WSVMA Annual Conference

Transcription

1 WSVMA Annual Conference Dairy Spokane Convention Center Spokane, Washington October 1-3, 2010 Ken Nordlund, DVM, DABVP University of Wisconsin-Madison School of Veterinary Medicine

2 Kenneth Nordlund, DVM, Diplomate ABVP (Dairy) University of Wisconsin Madison, WI Biography: Ken Nordlund is a Clinical Professor in the Food Animal Production Medicine group in the School of Veterinary Medicine at the University of Wisconsin-Madison. He was a private practitioner and practice owner in Fergus Falls, Minnesota from 1977 to In 1989, he joined the University of Wisconsin and helped to found the Food Animal Production Medicine program. His research interests include dairy record systems including development of the Transition Cow IndexTM and interactions between dairy cattle housing and health. Contact nordlund@wisc.edu

3 OBJECTIVE MONITORS OF TRANSITION COW MANAGEMENT PROGRAMS Kenneth Nordlund, DVM Diplomate, ABVP-Dairy Specialty University of Wisconsin-Madison, USA INTRODUCTION Approximately 75% of dairy cow disease events occur in the month following calving and are predicated by feed intake and immune function changes in the weeks prior to calving (Leblanc et al., 2006). How cows are managed through this window of time called the transition period can have major consequences on fresh cow health and subsequent performance. Records of disease events would seem to be a logical data source to evaluate programs, but the lack of standardized recording systems, coupled with inconsistent clinical case definitions and erratic recording practices renders on-farm health records nearly useless for comparative herd studies. In the past 5 years, we have moved toward more objective monitors based upon consistently recorded milk and component data, along with survival through the early lactation period. Our key monitors include the Transition Cow Index TM, 1 st Test fat:protein ratio, change in somatic cell count (SCC) between the prior lactation and the first test, and the turnover rate in less than 60 days-in-milk. TRANSITON COW INDEX TM Reduced milk yield is associated with each of the common fresh cow diseases (Edwards & Tozer, 2004, Østergaard and Gröhn, 1999). Because milk yield is commonly recorded in a standardized method through Dairy Herd Improvement Association (DHIA) services in the USA, it could potentially be used to monitor fresh cow health. A technique called Transition Cow Index TM has been developed where the actual 1 st test milk yield collected between 5-40 DIM is compared to a prediction of 1 st test milk yield (Nordlund, 2006). The prediction equations were developed using mixed models and the AgSource DHIA cow data from a two-year period merged with herd-level Posilac-purchase records supplied by Monsanto. The merged data set represented 4,025 herds. Effects used in the final model include DIM at first test (limited to the interval from 5-40 DIM), previous lactation milk, DIM in prior lactation, start of current lactation as calving or abortion, start of prior lactation as calving or abortion, month of calving, SCC log score at last test of prior lactation, days dry, milking frequency current lactation, milking frequency prior lactation, parity number, breed, and Posilac use at the herd level. TCI TM, the difference between actual and predicted first test milk, can be expressed as lbs on 1 st test day or as 1 st test projected 305-day milk. Commercial use of TCI TM by AgSource, the Wisconsin-based DHIA service, uses the 305-day projection version. We have data, as yet unpublished, showing that disease events are strongly associated with negative TCI TM scores. While individual cows can have very low first test milk yield records for many reasons other than disease, the herd average TCI TM appear to be reflective of overall transition cow management. 1

4 Because TCI TM values can be generated for all cows with a previously recorded lactation, herd average scores can be produced for all herds participating in DHIA testing programs. The 10 th, median, and 90 th percentile values for herd average TCI TM scores in our industry are -1,200, -32, and +1,050 lbs (AgSource, 2009). Using these as benchmark values can be a powerful motivator for many dairy operators in improving transition cow management. Herd managers can use to monitor the performance of transition cow management programs over time. In Figure 1, a graph of TCI values of individual cows are plotted according to calving date. In addition, monthly average values are printed above the graph and a rolling average value is presented as a red line moving through the individual cow values. Figure 1. Graph of TCI over 12 month period. A new special needs barn was constructed in June 2009 and the transition cows moved into the barn in July. Individual cow performance subsequent to her TCI TM score shows correlations with survival to 61 days, survival to another lactation, increased milk yield, and modest improvements in likelihood of pregnancy by 150 days in milk. Each increase of 1,000 lbs of TCI TM was associated with an increased survival rate into the next lactation of 2.4% and an increased lactational cumulative milk of 1,270 lbs. In the AgSource herd base, some over 2,000 lbs TCI TM separates the 10 th and 90 th percentile of herds. Using associated survival and milk yields, 2,000 lbs TCI TM should yield a gross economic difference approaching $500 per cow per year between the poorer and best programs. TCI TM offers an objective method to benchmark individual herd transition management programs, enhances options for field trials and surveys, provides economic information about the 2

5 value of programs, and offers a tool for ongoing monitoring of herd transition management programs. First test fat:protein ratio In addition to milk yield, DHIA organizations also determine fat and protein content of milk on a routine basis. Several researchers have examined associations between first test milk fat and protein and ketosis. Duffield and Bagg (14) defined ketosis problem herds as herds where more than 20% of the cows showed a serum beta-hydroxybutyrate concentration greater than 1400 umol/l. Using first DHIA test day data on protein % and fat %, problem herds were accurately identified if more than 40% of cows at first test had a protein to fat ratio of less than Geishauser et al (1997) used the inverse ratio of fat% to protein % for first test-day data as a monitor for displaced abomasum. Using a fat:protein ratio (FPR) of >1.4 on test day data captured at days in milk, the sensitivity and specificity for predicting a DA was 80% and 69% respectively. Heuer et al., (1999) used first test-day information from 1335 lactation records of cows in 16 dairy herds in the Netherlands to explore the risk of disease in cows with a FPR >1.5. First milk tests were collected at 18 ± 8 days in milk. Odds ratios for ketosis, cystic ovarian disease, mastitis, and lameness were 3.2, 1.7, 1.7, and 1.5 respectively. In addition, cows identified with ketosis prior to first test had a 4.4 fold increase in the rate of FPR >1.5 and left displaced abomasum increased the rate by 5.3 times. Care must be taken when using these ratios. For the guidelines above, milk protein is measured on a true protein basis. Some milk testing services use crude protein, not true protein, in their component testing. If crude protein is the measure used, the cut-point should be increased to 1.5 rather than 1.4. We have used the herd guidelines developed by Duffield et al (1997) of greater than 40% of the cows have a ratio greater than 1.4 as suggestive of herd at high risk for ketosis. As we work with the data from the ~5,000 herds in the AgSource client base (AgSource, 2009), we find that the average herd is considered a high-risk herd. In this population of herds, the 10 th, 50 th, and 90 th percentile herds have <22%, 44%, and >68% of cows with 1 st test FPR>1.4. It is sometimes suggested that high producing herds will have higher rates of ketosis and higher than average rates of 1 st Test FPR>1.4. However, our clinical work indicates that many of the truly elite transition cow programs in herds with average milk yields above 14,000 kg per cow per year show rates of high ratios at less than 25%. Change in SCC between last test of the prior lactation and the first test SCC One of the primary goals of transition management programs is the elimination of existing intramammary infections and the prevention of new infections. Monitoring SCC changes across the dry period is an important component of transition program monitoring. Somatic cell counts (SCC) at the first DHI test day can be used to monitor dry period mastitis management, using a threshold of 200,000/ml as an indicator of infection. Concern is occasionally expressed about false positives using this threshold in early lactation. However, 3

6 Barkema et al. (1999) monitored quarter SCC after calving and showed that in culture-negative quarters, 95% have a SCC less than 250,000/ml by the fourth milking. Because DHIA rules mandate that only SCC data from cows six days in milk or more are stored, composite milk from all quarters taken at the first test after calving can be used to assess the infection status of the udder. To track SCC changes across the dry period requires that the SCC from the last test date of the prior lactation is stored as such and paired with the 1 st test SCC of the new lactation. Stewart, et al, (Stewart et al, 1995) introduced a scatterplot technique to group cows according to changes in infection status across the dry period. All cows in their second or greater lactation are grouped into the following four categories: uninfected cows at dry off that remain uninfected, formerly uninfected cows that developed new infections, infected cows at dry-off that cured the infection, and infected cows that remain infected. Cook et al., (2002) described and presented benchmarks using this method from 145 Wisconsin dairy herds. More recently, data from the AgSource client base indicates the following benchmarks for our industry (AgSource, 2009). For formerly uninfected cows that developed new infections, the 10 th, median, and 90 th percentiles are <7%, 23%, and >43% respectively. For dry period cure rates, the 10 th, median, and 90 th percentiles are <45%, 64%, and >80% respectively. For first lactation cows, there are no SCC data from prior lactations. As benchmarks for the proportion of 1 st lactation cows infected at first test, the 10 th, median, and 90 th percentiles are <9%, 24%, and >41% (AgSource, 2009). Some precautions must be observed in using these benchmarks to make inferences about transition cow udder health management. Similar to the use of the single first test SCC, the new infection risk across the dry period reflects the interval between calving and first test in addition to the dry period. While the experience of the authors indicates that most new infections are related to the dry cow environment and sometimes dry treatment practices, there are occasions where inadequately maintained fresh cow milking systems and poor milking practices of fresh cows create new infections in the days between calving and the first DHI test. Conversely, the new infection risk of dry cows may be artificially suppressed by use of the California Mastitis Test and treatment of positive quarters at 2-3 days in milk, sometimes called the Fresh Start program (Fresh Start Program, Pfizer). This program will cure some infected quarters prior to the first test date, thus invalidating the use of this test as a primary monitor. In this situation, data must be interpreted in light of the proportion of cows receiving treatment prior to first test day. SURVIVING THE TRANSITION PERIOD: Turnover rate less than 60 DIM Dairy recording organizations most commonly use turnover rate to measure overall culling. Turnover rate, a traditional term used in business inventory monitoring (US Bureau Labor Statistics, 2004), is calculated by dividing the number of cows removed from the herd by the average number of cows in the herd during the same period of time and multiplying by 100. (Fetrow et al, 2006). Cows that leave the herd in the first 60 days after calving are usually removed because of disease or injury (USDA, 2002). Therefore, removal rates within the first few months can serve as a critical monitor of the efficacy of transition cow management programs. There are exceptions to the general assumption that early lactation culled cows are the 4

7 result of transition management failures, such as dairy sales and cows removed because of positive test results in Johnes disease eradication programs. In most situations, such exceptions are unusual. We calculate early lactation culling as a herd turnover rate of cows removed before 60 days in milk (TOR <60 DIM). By presenting early culling losses as a percentage of the herd rather than as a percentage of culls, early lactation culls can be compared between farms. Based upon data from ~5,000 herds in the AgSource client base (AgSource, 2009), the average herd has a TOR<60 DIM of 9.0 %, the highest 90th percentile is >13% and the lowest 10% percentile is <5%. SUMMARY In recent years, transition cow monitoring has shifted away from disease event rates and toward consistently collected data based upon milk yield, milk components, and cow turnover in early lactation. Table 1 outlines the key indices and benchmarks that we use in our herd consulting services. By using these monitors, effective transition cow programs can be differentiated from problematic ones and many of the problems can be resolved for the good of the herd owners, dairy laborers, and most of all, the cows. Table 1. Key Performance Indicators for Transition Cow Management Poor Average Excellent TCI TM, Lbs -1, ,050 1 st Test FPR>1.4 >68% 44% <22% SCC across Dry Period Dry Cow New Infections >41% 23% <7% Dry Cow Cures <45% 64% >80% SCC>400K, 1 st lactation cows >41% 24% <9% TOR<60DIM >13% 9% <5% BIBLIOGRAPHY AgSource Cooperative Services. Herd Summary Averages page. Available at: Accessed on: March 26, Barkema HW, Deluyker HA, Schukken YH, Lam TJGM. Quarter-milk SCC at calving and at the first six milkings after calving. Prev Vet Med 1999;38:1 9. Cook NB, Bennett TB, Emery KM, Nordlund KV. Monitoring nonlactating cow intramammary infection dynamics using DHI somatic cell count data. J Dairy Sci 2002;85(5): Duffield, T.F., Kelton, D.F., Leslie, K.E., Lissemore, K., Lumsden, J.H. Use of test day milk fat and milk protein to predict subclinical ketosis in Ontario dairy cattle. CVJ 38: ,

8 Duffield T, Bagg R Herd level indicators for the prediction of high-risk dairy herds for subclinical ketosis. In: 35 th Annual Meeting of the American Association of Bovine Practitioners. Rome, GA; 2002, p Edwards JL, Tozer PR. Using activity and milk yield as predictors of fresh cow disorders. J Dairy Sci 2004;87(2): Fetrow, J., K. V. Nordlund, and H. D. Norman Invited Review: Culling: Nomenclature, Definitions, and Recommendations. J Dairy Sci 89: Geishauser T, Leslie K, Duffield T, Edge V. Fat/protein ratio in first test milk as test for displaced abomasums in dairy cows. J Vet Med A 1997;44: Heuer C, Schukken YH, Dobbelaar P. Postpartum body condition score and results from the first test day milk as predictors of disease, fertility, yield, and culling in commercial dairy herds. J Dairy Sci 1999;82(2): LeBlanc SJ, Lissemore KD, Kelton DF, Duffield TF, Leslie KE Major advances in disease prevention in dairy cattle. J Dairy Sci 89: Nordlund, K Transition Cow Index TM. In: Proc. 39th Ann. Amer. Assn. Bov. Pract., Auburn, AL. pp Østergaard, S., Y. T. Gröhn. Effects of Diseases on Test Day Milk Yield and Body Weight of Dairy Cows from Danish Research Herds. J Dairy Sci : Stewart S, Fetrow F, Eicker S. Field use of DHIA somatic cell counts with scatter graphs. Compend Contin Educ Pract Vet 1995;17(11): U.S. Bureau of Labor Statistics. Job Openings and Labor Turnover Survey. People are Asking page. Available at: Accessed May 25, USDA Part III: Reference of Dairy Cattle Health and Health Management Practices in the United States, USDA:APHIS:VS, CEAH, National Animal Health Monitoring System, Fort Collins, CO #N

9 KEY RISK FACTORS FOR TRANSITION COWS IN FREESTALL DAIRIES Kenneth Nordlund, DVM Diplomate, ABVP-Dairy Specialty University of Wisconsin-Madison, USA INTRODUCTION The objective monitor Transition Cow Index TM (TCI; Nordlund, 2006) has allowed us to study the overall effectiveness of transition management programs across a wide range of dairy herds. In 2005, we surveyed the transition management practices of 50 Wisconsin freestall herds. The herds, some over 600 cows, were selected from a stratified ranking of herd average TCI values; meaning that equivalent numbers of herd were selected from each TCI category, i.e., <-1,500, - 1,500 to -500, -500 to +500, etc. A wide range of management practices, housing characteristics, and animal evaluations were recorded. While the formal report of this survey has not yet been published, 5 factors emerged as the primary factors associated with herd average TCI scores. The 5 factors that have emerged are: 1) bunk space in both the pre-fresh and fresh cow pens; 2) minimizing pen moves and social stress in the peripartum period, particularly during the 10 d prior to calving; 3) increasing cow comfort through the period with amply sized stalls; 4) sand resting surfaces on which to lie; and 5) an efficient and effective screening process to identify cows needing medical attention or nursing care. Further refinements of these factors have been made using clinical data gathered in field investigations of problem dairies by the Food Animal Production Medicine group at the University of Wisconsin. We are now using these 5 factors as the primary focal points as we work to improve fresh cow health with our clients. FIVE FACTORS Bunk space Sufficient space at the feeding fence for all transition cows to eat simultaneously appears to be the most important determinant of transition cow performance in our current industry. Essentially, we are recommending a minimum of 76 cm of bunk space/cow in pre-fresh and postfresh pens for a 90-min period after fresh feed is delivered and after every milking. For a discussion of these issues, please read the article referenced at the end of this section (Nordund et al., 2006). To determine feeding space/cow, it is important to measure the length of the feed fence. If the feeding fence is fitted with self-locking stanchions, do not assume that a cow can feed in each stanchion. Our video studies show that lactating cows fill a row of standard 61-cm headlocks to a maximum of 80 % at peak feeding periods, regardless of the number of cows in the pen. This suggests that in fresh pens, cows will fill to a space of about 76 cm. It is likely that prepartum cows would benefit from even more space than lactating cows. Calculation of feeding fence space/cow in the transition pens on a single day may not represent the typical situation, because of the variation in the number of cows calving each week throughout the year. It will be helpful to estimate the typical stocking pressure in the pre-fresh and post-fresh pens. First, calculate the average number of calvings/wk by dividing the total number of calvings in the past year by 52. Multiply the average number of calvings/wk by the 7

10 target number of weeks in the pen. If the feeding fence space goal of ~ 76 cm/cow is reached with the average expected number of cows in the pen, then the pen will typically be over-stocked half of the time. In most situations, provision of space for 140 % of the average expected number of calvings will meet the goals for bunk space more than 90 % of the time. During periods of pressure, most dairy managers reduce the number of days that individual cows reside in these pens. However, it is preferable to minimize these adjustments of time in special management pens. These recommendations for 30 in of space assume that the pens are equipped with lockups or other vertical dividers between feeding spaces. If the cows are fed at a post-and-rail feeder, additional space should be provided as dominant cows appear to clear subordinates sooner in these situations (Endres et al., 2005). Pen moves and social stress versus stable social groups Each pen move requires that a cow familiarize herself with the surroundings, as well as reestablish a pecking order within the group (Hasegawa et al., 1997). More recent work has shown reduced time spent eating, increased feed evictions, and reduced milk yield following a pen move (von Keyserlingk et al., 2008). Minimizing the number of regroupings through the transition period is consistent with successful transition programs. In most situations, steps to reduce any moves will result in improved transition performance. Cows are social animals. Isolation from the herd creates stress for a cow and separating a single cow into a separate calving pen for more than a couple of days appear to be high risk practices. However, movement into a new social group also creates stress as the cow establishes rank within the group. The first 2 d after a move into a new group are characterized by a dramatic increase in the number of agonistic interactions, most of them physical (Kondo and Hurnik, 1997). If no additional new cows enter the pen, the group becomes relatively stable. A concept of social turmoil profile of a pen has been described (Nordlund et al., 2006). In pens where cows enter at intermittent intervals, like a week or more, extended stays in such pens are considered desirable. However, pens where cows enter and leave on a daily basis are considered to be in constant social turmoil and every effort should be made to minimize the time that prepartum cows spend in these pens. Close-up pens There are many different approaches to close-up and calving pens. The basic idea that we bring to an evaluation of pen moves is that there is a period of about 2-3 d of social turmoil within a pen after new cows enter. In the pre-fresh period, we want to minimize the risks for development of fatty liver and Type II ketosis. The optimal entry policy for a close-up pen would be an all-in pen where a cohort of cows due to calve within a short period of time, such as a 1 wk to10 d, are assembled with no further additions through the calving process. Less optimal would be weekly entries of new cows into the close-up pen; and even less attractive are daily entries of new cows into the pen, which result in pens of constant social turmoil. 8

11 We have begun to see dairies establish stable social groups as early as dry-off. Dry cow housing consists of a series of pens, each sized to hold approximately 15 to 20 % of the total number of dry cows. Each pen is filled over a period of a week to 10 days and the group in each pen is kept together without the addition of new cows through calving. Calving pens Calving pens can refer to either a pen to which a cow is moved hours before delivering her calf or it could be a close-up pen where cows enter several weeks before their anticipated calving date and deliver the calf within the pen. If the calving pen has a stable social structure (no additions), extended stays are fine. If new cows are continually being added, we recommend that the duration of stay be limited to 48 hr maximum. Clinical data from field investigations by the Food Animal Production Medicine group at the University of Wisconsin show dramatic increases in ketosis and displaced abomasums and early lactation culling of cows that stay 3-10 d in daily-entry group calving pens (Nordlund et al., 2006). When cows are moved on a daily basis to daily-entry calving pens, they should be selected carefully so that minimal numbers spend more than 48 hr in these high turmoil pens. It has become common to move cows to calving pens when feet are showing. Moving cows to calving pens once calving has begun effectively minimizes the time in high turmoil pens, but presents a new set of challenges. First, it requires round-the-clock labor to check and move cows. Freestall pens can be designed to facilitate this practice with the construction of two-row head-to-tail arrangements of the stall rows. With the tails of all cows visible from the central feed alley, the observer can monitor each cow without walking through and disrupting the pen. Second, workers must be monitored carefully in that they should not move cows into calving pens too early. In a report on moving cows when calving was imminent (Carrier et al., 2006), cows that were moved when in labor but with only mucus showing had 2.5 times the rate of stillbirths as cows that were moved when the calf s feet or head were showing. When the closeup cows are in freestalls, there is a tendency of laborers to move cows into calving pens too early. By moving cows into the pens early, fewer calves are born into the alleys and workers can avoid soiling their clothing when picking up slurry-covered calves. Isolation pens, i.e., box stalls would appear to minimize social turmoil, but cows are social animals and separation from the herd is usually a stressful experience. If cows are moved to individual box stalls for calving, the duration of stay should be limited to a matter of a few hours. Bedded pack all-in pens with the combined function of pre-fresh period and calving are considered optimal. There are several ways to achieve this goal, but a feasible strategy requires a minimum of 3 pens, one may be freestalls and the last two would be bedded packs. On a weekly move day, for example, the new group of cows on the calving pack would be 0-7 d before due date. The new cows on the second pack would be 8-14 d before due date, and the new group of cows in the close-up freestalls would be d before due date. Cow groups stay intact as they move on a weekly basis from pen to pen. After calving, the individual cow and calf are removed and transferred to appropriate pens. To avoid the stressful experience of being left alone in a pen, the last two cows remaining to calve should usually be commingled with another pen when that situation arrives. 9

12 Amply sized freestalls or bedded packs A deeply bedded pack is the preferred housing for close-up cows in confinement housing. The guideline of 100 sq ft of space/cow (Bickert, 2000) includes the bedded area only and assumes that cows have access to an external feeding alley or outside lot. If the feeding area is continuous with the bedded pack, the space should provide a minimum of 120 sq ft/cow with good bedding covering most of the area. The pack should be sized to accommodate surges in cow numbers. The estimated number of cows calving/wk is estimated by the annual number of cows calving by 52 wk/yr. If the plan is to leave cows in a pen for 3 wk, the average pen population would be expected to hold 3 x the number of average calvings/wk. If the pen is sized to handle 140 % of the average population, it will provide the goal space for each cow approximately 90 % of the time. If freestalls are used, sand is the preferred material because it presents relatively low risk for mastitis compared to organic products. However, any deep, loose surface will be an improvement over a hard surface. Mattresses covered with modest quantities of shavings or other materials are viewed as average, and any stall surface such as concrete or other firm packed materials covered with modest bedding should be considered a high risk to successful transitions. Freestall size Prepartum freestalls, in particular, need to accommodate the ample dimensions of pregnant cows and allow for some clumsiness in their rising and lying motions. Stalls for prepartum Holsteins and Jerseys should be at least 127 and 114 cm wide respectively. Length is the distance between the outer corner of the rear curb to the point where the stall surface touches the brisket locator. If there is no brisket locator, the total stall length is the stall resting length. This distance should be greater than 178 and 160 cm for Holstein and Jersey cows respectively. Appropriate dimensions have been developed for cows of other breeds and various sizes (Nordlund and Cook, 2003; Cook and Nordlund, 2005). Evaluating the potential for lunge, bob, and rise should reflect assessments of 3 separate items in a freestall: a brisket locator that does not restrict rising motions including the forward swing of the front foot, freedom from impediments to the forward lunge of the head and shoulder, absence of bob zone obstructions, and the neck rail being sufficiently high and forward (Nordlund and Cook, 2003; Cook and Nordlund, 2005). For a stall to be considered low risk for Holstein cows, the total stall length should be at least 3 m long with no obstructions to forward lunge and bob. If the stall is less than 3.0 m, but the lower side rail is 11 in above the stall bed or less, it will allow for side lunging but is still considered an average risk for transition cows. If the stall is less than 2.4 m and has obstructions to side lunging, such as lower divider rails greater than 33 cm above the stall bed, the stalls present major risks to successful transition performance. Finally, the neck rail should be approximately cm above the stall surface. Effective screening program for cows needing attention While difficult to assess, the primary determinant of the fresh cow screening and treatment program is the quality of the people and how much they care for the cows. Facilities that allow easy restraint without exciting the cows is also critical to these programs. 10

13 The optimal screening programs appear to use some form of appetite assessment. The practices of the herdspersons of the elite transition programs in our survey study were remarkably similar: placement of fresh TMR while fresh cows were being milked, observation of them returning to the pen, self-locks engaged, and assessment of appetite and attitude. Similarly, the herdspersons in the elite herds knew and cared about the fresh cows under their watch. Obviously, this requires both special people and facilities. The bunk space issue returns in screening. In order to evaluate appetite of all cows, there must be sufficient feeding space for all cows to eat simultaneously. Cows that do not lock-up, or cows that lock-up with suppressed appetite or signs of depression were examined. Other examination procedures including rectal temperature, observations for vaginal discharge, ketosis, displaced abomasum, lung sounds, etc., were conducted when primary assessments indicated further evaluation. While formal screening programs in lockups for fresh cows are a desirable practice, the procedure needs to be efficient and not interfere significantly with the daily time-budget of the fresh cows. Screening procedures that lock cows up for a period of 1 hr or less/d are considered optimal. While cows are quite capable of compensating for a 1-2 hr change in routine, if lock-up is prolonged and in association with other stressors, such as overstocking, then the ability of the cow to compensate and catch-up on lying time may be exceeded. Cooper et al. (2007) showed that when cows were deprived of lying for 2-4 h/d, they only managed to recover approximately 40 % of the lost lying time by 40 hr after the deprivation. Extended lockup time adds substantially to the stresses of transition. The location of the screening procedures has a substantial impact on the time constraints. If the cows have access to feed while being examined, feeding and the screening can proceed almost simultaneously. Screening time at a palpation rail, for example, must be weighted as riskier than equivalent time in lockups over feed. This antagonism between holding time and the thoroughness of the screening procedure puts some severe constraints on the fresh pen. Disclaimer Obviously, this list is not comprehensive. There will be many potential risks to individual transition programs that are not listed. However, the risk factors presented here are considered to be common problems in today s intensively managed freestall dairies. BIBLIOGRAPHY Bickert, W.G Chapter 4. Milking Herd Facilities, in Dairy Freestall Housing and Equipment, MWPS-7, Seventh Edition. Ames, Iowa, Midwest Plan Service, Iowa State University, Ames, IA. Carrier, J., S. Godden, J. Fetrow, S. Stewart, and P. Rapnicki Predictors of stillbirth for cows moved to calving pens when calving is imminent. In: Proc. 39 th Ann. Amer. Assn. Bov. Pract., Auburn, AL. pp Cook, N. B., and K.V. Nordlund An update on dairy cow freestall design. Bov. Pract. 39:

14 Cooper, M.D., D.R. Arney, and C.J.C. Phillips Two-or-four-hour lying deprivation on the behavior of lactating dairy cows. J. Dairy Sci. 90: Endres, M.I., DeVries, T.J., von Keyserlingk, M.A.G., and D.M. Weary Short Communication: Effect of Feed Barrier Design on the Behavior of Loose-Housed Lactating Dairy Cows. J. Dairy Sci. 88: Hasegawa, N, A. Nishiwaki, K. Sugawara, and I. Ito The effects of social exchange between two groups of lactating primiparous heifers on milk production, dominance order, behavior and adrenocortical response. Appl. Anim. Behav. Sci. 51: Kondo, S., and J.F. Hurnik Stabilization of social hierarchy in dairy cows. Appl. Anim. Behav. Sci. 27: Nordlund, K.V., and N.B. Cook A flowchart for evaluating dairy cow freestalls. Bov. Pract. 37: Nordlund, K Transition Cow Index TM. In: Proc. 39 th Ann. Amer. Assn. Bov. Pract., Auburn, AL. pp Nordlund, K., N. Cook, and G. Oetzel Commingling dairy cows: pen moves, stocking density, and health. In: Proc. 39 th Ann. Amer. Assn. Bov. Pract., Auburn, AL. pp von Keyserlingk, M., D. Olenick, and D. Weary Acute behavioral effects of regrouping dairy cows. J. Dairy Sci. 91:

15 ADVISING CLIENTS IN BUILDING OPTIMAL TRANSITION COW HOUSING Kenneth Nordlund, DVM and Nigel Cook, MCRVS University of Wisconsin-Madison, USA INTRODUCTION Over the last few years, our Food Animal Production Medicine group at the University of Wisconsin-Madison has used our clinical experiences troubleshooting fresh cow health problems on farms and research conducted by other groups and ourselves to formulate a plan for designing transition cow barns which results in optimal health and performance. In this article, the planning process we have devised and used successfully to create these new facilities is summarized. WHERE TO START? The planning process starts with one simple question: How am I going to manage my cows at the point of calving? Clinical data from field investigations by the Food Animal Production Medicine group at the University of Wisconsin show dramatic increases in fresh cow disease for cows that stay 3-10 d in daily-entry group calving pens (Nordlund et al., 2006). To avoid this risk, two strategies are considered. Cows can calve in the close-up pen, or they can be moved just-in-time to specific calving pens. Bedded packs and open-lots can be appropriate for the combined service of close up housing and calving. The just-in time move to a calving pen is a common practice with cows housed in freestalls, but can be used in conjunction with bedded packs and open lots. The just-in-time move requires a round-the-clock labor force where the close up pen is checked hourly for cows in early stages of labor, and this is typically available for herds of about 600 cows and greater. JUST-IN-TIME CALVING PENS PARAMETER CALVING IN THE CLOSE- UP PEN Freestalls, bedded pack, or open lot Less roof space required, but increased floor and stall construction costs in freestalls Limited to stall bedding and bedding for individual or group calving pen Need to check prefresh pen hourly 24/7 Elevated if workers move cows too early (Carrier et al, 2006) Good, provided hygiene is excellent in the pen Type of Housing Space Requirement and Cost of Construction Bedding Costs Labor Risk for dystocia Bedded pack or open lot More roof space required, but no stall construction costs High due to the use of multiple bedded packs Less need for constant supervision Decreased, as cows do not have to be moved when they are in labor Exposure to infectious disease More exposure time to dam, allowing for increased Johne s and other risk Excellent opportunity for Passive Colostrum administration is more 13

16 colostrum administration immediately after birth Immunity Transfer likely to be delayed because if greater intervals between visits Just-in-time calving pens If cows are moved just-in-time, keys to success are: 1) a correctly designed pen, such as the one shown in Figure 1 below, 2) calving pens located close to the prefresh pen and away from heavy traffic areas, 3) excellent hygiene in the pen with fresh, dry bedding that arrives with the cow and leaves with the cow, 4) maternity pen workers who are trained to identify the stages of labor and who do not move cows into the pen too early with only mucus showing. Figure 1. An excellent maternity pen layout with a concrete apron against the feed bunk in the foreground, a bedded area with sand covered with straw in the rear half of the pen, and a head gate in the far corner. The water trough is located away from the bedded area in the feeding area. 12 Head-gate Swing gate 12 Bedded calving area Calving in the close-up pen If the cow delivers her calf in the close-up pen, special attention must be paid to maintaining a clean environment, for which the key determinant is stocking density. Feed Bunk If the pen is a bedded pack, it should provide a minimum of 100 square feet of bedded area per cow at maximum Water trough fill. The pen is bedded fresh daily with sufficient bedding that feces are not visible without moving bedding aside. If the pen is an open-lot, there should be a minimum of 650 sq ft per cow at maximal stocking density with a minimum of 50 sq. ft. of shade (Armstrong, 2010). Supervision is still required to make sure that assistance with dystocia and administration of colostrum is timely. One disadvantage is that identification of dam and calf pairs with sometimes be difficult when there have been multiple deliveries overnight. GROUPING STRATEGIES PRIOR TO CALVING Traditional move to close up pen 3 weeks before due date Because every pen move requires that cow re-establish social rank, it is desirable to avoid pen moves during the vulnerable time windows in the weeks before and after calving. For decades, dairy managers have moved cows from the dry cow pen into a close up pen approximately 21 days prior to due date. Usually, these moves are completed once per week. Although cows already residing in the close up pen have some seniority and may be approaching their due date, they must still establish their rank with the newcomers. Any disruption that reduces or destabilizes dry matter intake in the week prior to calving increases risk for fresh cow problems. Stable social groups prior to calving Bedding retainer Concrete feed alley 12 14

17 Anecdotal reports from dairies who establish stable social groups in the transition period suggest that there are substantial benefits for fresh cow health. Stable social groups can be formed at dry off or they can be established for the last 3 weeks in close up pens. The optimal strategy appears to be to dry off a cohort of cows together and let them establish a stable group at that time. The expected calving dates could span a one to two week window. In a large herd with a 55-day dry period, for example, it may be appropriate to have a total of six dry cow pens with cohorts of cows due within 10 day windows. In general, the original cohort of cows in one pen would remain intact throughout the period with no additions to the pen and no removals until calving. In practice, it is typical to need to make a number of pen changes of cows that were dried off early so that they can be placed in a pen of cows with similar due dates. It is best to make these adjustment moves at least 20 days before due date. In addition to the advantage to the cows, these strategies offer benefits for labor. No longer is the entire dry cow pen being locked up once or twice a week so that cows can be identified and moved to the close up pen. If a just-in-time calving pen is used, proximity of cows to those pens is important. In this system, the cows just recently dried are furthest from the calving pens, and intact stable groups move sequentially from pen to pen to gain proximity to the calving pens. The pens can be either freestalls, bedded packs, or open lots. Some cows will go well beyond their expected calving date. Practical experience indicates that when the pen gets down to a couple of stragglers, they should be mixed with the next group. Once the pen is empty, it is cleaned and re-bedded and the filling cycle repeats. SIZING THE PENS CORRECTLY The actual duration of stay within any given transition cow pen (which includes the far-dry, prefresh, maternity, calving, colostrum and postfresh management groups) is determined by two factors; the rate of calving and the target duration of stay in the pen. Traditional approaches to pen sizing are based upon the average number of calvings per week times the number of weeks in the pen. For example, planning manuals for a 1,200 cow dairy would divide the # of cows by 52 weeks to yield an estimated 23 calvings per week (Figure 2.) If they spend 3 weeks in the close-up pen, the pen would be sized for 69 cows. However, sizing pens for the average means that the pen is overstocked half of the time. Considering the negative impact on fresh cow health, a better approach is to build the transition pens so that they are rarely overstocked. Using data from 73 large Midwest US herds, sizing pens for 140% of the weekly average will yield overstocked pens only 10% of the time. 15

18 Steps to Determine Pen Figure 2. Calving rate by week for a 1200 cow dairy with Size average (solid line) and 90 th percentile (dotted line) calculated. 1. Calculate the average 50 weekly rate of 45 freshenings for the herd. 40 For herds that are 35 remodeling, we can 30 graph this in 25 programs like DC and file out the data into Excel. For new 15 herds, we estimate the 10 number of calvings to 5 be 104% of the 0 rolling average number of cows in the herd, and the weekly Date rate will be this number divided by 52. For example, a 1,000 cow dairy will freshen 20 cows and heifers per Number of Calvings Per Week 11/13/ /13/2004 1/13/2005 2/13/2005 3/13/2005 4/13/2005 5/13/2005 week on average. 2. Calculate the 90 th percentile of the weekly calving rate or 140% of the weekly average. In the example 1,200 cow dairy from Figure 2 above, multiply the weekly average of 23 times 1.4 to yield the 90 th percentile threshold of 32 cows. 3. Determine the target duration of stay in each transition cow pen. Factors such as target dry days, time of return of heifers to the close-up or far-dry pens, days in prefresh, time in the calving or maternity pen, and days in postfresh need to be decided. These are management decisions that will be farm dependent. 4. Calculate the number of cows in each group. Using the same example above, a postfresh pen sized to accommodate these cows to 21 DIM would need 96 stalls (32 cows x 3 wks). We have brought these ideas together in a pen size calculator for use on farm available at An example output is shown in Figure 3 for a 1000 cow dairy with a 60 day dry period and 21 days spent in the pre- and post-fresh pens. 6/13/2005 7/13/2005 8/13/2005 9/13/ /13/ /13/ /13/2005 1/13/2006 2/13/2006 3/13/2006 4/13/2006 5/13/2006 6/13/2006 7/13/2006 8/13/2006 9/13/ /13/2006 Once we know the inventory in each group that we need to build for, we can proceed with the rest of the building design. MINIMUM DESIGN Figure 3. Pen size calculator Heifers Cows Total Weekly Calvings (140% of average) Days in Pre-Fresh Pen Days in Calving Pen Days in Post-Fresh Pen Average Days Dry NA Days pre-calving to return to the dairy 30 NA 30 Far-Off Dry Cow/Heifer Inventory Pre-Fresh Pen Inventory Calving Pen Inventory Post-Fresh Pen Inventory

19 REQUIREMENTS Using the calculated pen inventory as a starting point, we can now determine the dimensions and layout of each pen, using the following minimum stall and feedbunk requirements: 1. At least one stall per cow pre- and post-fresh. 2. Stalls should be of adequate width, resting area and length to accommodate heavily pregnant pre-fresh cows. 3. Stalls should have a soft giving surface with good cushion, traction and support and ideally have a sand base. 4. There should be a minimum of 30 inches of bunk space per cow for pre- and post-fresh cows, in order allow all of the cows to eat at the same time. 5. Allow a target of 24 inches of bunk space per cow for far-dry cows and heifers. 6. For bedded packs, provide a minimum of 100 square feet of bedded area per cow Using the above requirements we know from the predicted inventory how many stalls are desired (or square foot of bedded area) and we can calculate the feed bunk length of each pen. For example, a 1200 cow dairy would need a 21 day prefresh pen feed bunk that was 96 x 2.5 feet = 240 feet long. PEN AND BARN LAYOUT To accommodate these recommendations for stalls and bunk space, freestall barns for transition cows should be built with only 2 rows of stalls. For ease of cow identification, head to tail is preferred for farms where pen workers need to check cows for signs of labor every hour. Pens of around 30 stalls split with a foot crossover with a water trough in the middle provide flexibility to cope with changing numbers of cows in each group over time (Figure Figure 4. A 2-row head to tail layout around a cross-over with a waterer 12 stalls 12 stalls 18/19 stalls 18/19 stalls 4). Stall width should be determined based on the size of the cows using the pen, with a typical range of between 48 and 54 inches for Holstein cows and heifers stalls per 48 wide = 29.4 bunk per cow 31 stalls per 50 wide = 30.6 bunk per cow 30 stalls per 54 wide = 32.4 bunk per cow 17

20 An example layout for a 1,000 cow facility is shown below in Figure 4. It provides for far-dry cows, split groups of prefresh cows and heifers, individual calving pens, a postfresh monitoring pen and a sick cow bedded pack, with a transfer lane around the perimeter. Figure 4. An example special needs barn layout for a 1000 cow dairy. Once a stylized barn layout has been agreed upon and sketched out, it is time to consult with builders and engineers to put the final plan together. Pre-fresh 29 heifers Far dry 96 cows Pre-fresh 55 cows Calving pens Sick Pen sq ft Post-fresh 52 cows ECONOMICS A special needs barn to support a 1,000 cow dairy with prefresh and postfresh pens built to accommodate 140% of the average weekly calving rate would require 60 more stalls than a facility built to accommodate the average. At $3,500 per stall, this equates to $210,000 or $210 per cow in the herd. Based upon an amortization schedule using a 10-year repayment period and 10% annual interest rates, the annual payment would be $34.18 per cow per year for the extra stalls to accommodate 90% of the ebb and flow of calving rates. If we assume that feed costs account for half of the price of milk, each cow would need to generate an additional $70 in milk income per year. Based upon $14 cwt milk, this would require an additional 500 lbs of milk per cow per year to pay for building to the surge! Our preliminary data suggests that provision of the additional space and stalls will yield an increased TCI of more than 1,000 lbs, which translates into approximately 1,250 lbs of milk and a reduced turnover rate of more than 5%. We have not tried to estimate reduction in drug and veterinary costs. The economics of a properly sized special needs barn appear to be easy. REFERENCES Cook, N.B, and Nordlund K.V. (2004). Behavioral needs of the transition cow and considerations for special needs facility design. Pages In: Veterinary Clinics of North America, Food Animal Practice: Managing the Transition Cow to Optimize Health and Productivity. November 2004, Volume 20, Number 3. W.B. Saunders Co. Nordlund, K., N. Cook, and G. Oetzel Commingling dairy cows: pen moves, stocking density, and health. In: Proc. 39 th Ann. Amer. Assn. Bov. Pract., Auburn, AL. pp

21 Carrier, J., S. Godden, J. Fetrow, S. Stewart, and P. Rapnicki Predictors of stillbirth for cows moved to calving pens when calving is imminent. In: Proc. 39 th Ann. Amer. Assn. Bov. Pract., Auburn, AL. pp Armstrong, D. Dry Lot Dairy Management National Mastitis Council Annual Meeting Proceedings. Page

22 UPDATES TO A FREESTALL EVALUATION FLOWCHART Ken Nordlund, DVM Diplomate, ABVP-Dairy University of Wisconsin-Madison, USA INTRODUCTION TO FLOWCHART 20

23 This article updates an original publication entitled Flowchart for evaluating dairy cow free stalls (Nordlund and Cook, 2003). The original article can be accessed at our website < >. This serves as a companion piece, updating that flowchart with new knowledge gained through research or through practical experience learned from implementing new designs. Resting Surface Cushion and Traction Sand has emerged as the gold standard for bedding of dairy freestalls because it is associated with major reductions in the prevalence of lameness (Cook et al, 2004, Espejo et al, 2006) and with cleaner udders (Cook, 2004) when compared to mattress freestalls. We relate this difference in lameness to the alteration of standing behavior of lame cows on mattresses, whereas lame cows do not alter behavior on sand (Cook et al, 2004). Hygiene scores in cows in sand herds are on average better than for cows in mattress stall herds (Cook, 2004). Table 1. Least squares mean (SE) hygiene scores (Proportion scoring 3 and 4 for each zone using a 4-point scale to assess degree of cleanliness) in the high group pen on 12 free stall herds (6 sand and 6 mattress). Sand Herds Mattress Herds SE P Udder Lower Leg Upper Leg and Flank Adequate and defined resting space Since our previous article, research has shown that increasing stall surface area has an impact on resting and standing behavior. A Canadian study found that cows lay down for 1.2 h/d longer in wider stalls (52 compared with 44 inches wide) and spent less time standing in the stall (Tucker et al, 2004). The most recent recommendations for resting area place stall widths at 48 inches for first lactation heifers, 50 inches for mature cows and 54 inches for pre-fresh cows (Figure 1), measured between dividers on center (Anderson, 2003, Cook, 2004). Where mixed ages and sizes are penned together, we suggest using the 48 inch dimension, or be prepared to tolerate dirtier stalls. The distance from the rear curb to the brisket locator should be 68 to 70 inches for first lactation heifers, and 70 to 72 inches for mature cows, depending on their size. 21

24 We have also begun to appreciate more the impact on cow movement and behavior of how the stall area is defined. The brisket locator should be no higher than 4 inches above the stall surface so that the cow could lie with one forelimb extended if she chose to, and be able to thrust the fore-limb forward during the rising motion (Nordlund and Cook, 2003). Recent studies have indicated that cows prefer stalls without a brisket locator (Tucker et Figure 1. A rounded and sloped concrete brisket locator is present in these stalls, but covered with al, 2006). However, our clinical sand. The edge of the brisket locator is indicated by experience indicates that small the canvas hem in the photo below. cows are frequently poorly located in stalls without brisket locators, frequently lying too far forward and resulting in fecescontaminated stalls and udders. We have been working with a sloped and rounded concrete brisket locator design that has performed successfully to position small cows properly, yet allow large cows to sprawl over it as shown in Figure 1. Plans are available at the website: f Room to lunge and bob room 22

25 New barns continue to be built Figure 2: Dividers mounted on a single beam located with obstructions to the lunge above the lunge and bob zone. and bob movements of the head. The most common mistakes being made are mounting of the stall dividers on structures that prevent forward lunging. The most problematic are horizontal mounting bars located 10 inches or more above the surface of the stall and will impede the head-bob movement when lying down and rising. However, if the freestalls are mounted on the single beam that sits at least 36 inches above the stall surface (Figure 2), the front becomes open and consistent with excellent lunge and bob space. For head-to-head stalls, we are recommending a 17-ft base for Holstein cows to minimize social obstructions to entry and rising. If one cow occupies a stall on a head to head platform that is only 15 feet long, she becomes a social barrier to another cow lunging into the shared space, resulting in reduced stall usage and reduced lying time. s Correct Neck Rail Location No other part of stall design has given us as many problems as correct location of the neck rail both vertically above the stall bed and horizontally from the rear curb. Current recommendations put the vertical height above the stall surface at 48 to 50 inches in mattress stalls (Anderson, 2002). In loose bedded sand stalls, the aim must be to maintain the neck rail between 44 and 50 inches above the bedded surface (Cook, 2004). 23

26 The more difficult position is the horizontal location of the neck rail. It is common to find the neck rail located at 57 to 68 inches from the rear curb in both sand and mattress stalls a huge variation, suggesting that we are not providing farmers with advice that works in practice. In a mattress stall, the neck rail should be located vertically above the brisket locator or around 68 to 72 inches from the rear curb, depending on the size of the cow. This location should allow the cow to stand square in the stall with all four feet on the platform, while still ensuring that most of the manure falls into the alley if the cow defecates. The situation is complicated by the presence of the rear curb in the loose bedded stall as cows prefer not to stand with their rear feet on top of a sloped or rounded curb. To avoid this, they frequently stand diagonally and with their rear feet in the sand, resulting in defecation in the corners of the Figure 5. Correct location of the neck rail in a loose bedded stall with a stall bed. Based raised rear curb by moving the rail back from above a correctly positioned brisket locator a distance equivalent to the width of the rear upon clinical curb. records of Move the neck rail back from mastitis and above the brisket locator a distance equivalent to the lameness, we width of the curb. recommend a more aggressive location of neck rails in sandbased stalls or any other loose bedding material. Essentially, the neck rail is located about 6 inches further to the rear than in equivalent sized mattress stalls as shown in Figure 5. Our recommendation for stalls with loops that locate the neck rail 44 to 50 inches vertically above the stall surface, is to move the neck rail from above the brisket locator toward the rear by about 6 inches. In a mature cow sand stall with 72 inches from the rear lip of 24

27 the curb to the brisket locator, the neck rail should be located 72 6 = 66 inches from the rear lip of the curb. For first lactation heifers with 68 inches from the rear curb to the brisket locator, the neck rail should be located 68 6 = 62 inches from the rear lip of the curb. In stalls with neck rails lower than 44 inches, the farmer must be prepared to raise the neck rail location to ensure that the cow can rise without hitting the rail. RESPONSES OF THE COW TO STALL DESIGN PROBLEMS Lame cows The ability of a lame cow to rise and lie down will be further compromised by stall design problems such as inadequate resting area, low neck rails that are too near the rear curb, brisket locators that are too high and impediments to lunge and bob. While sand appears to help lame cows to compensate for some design faults, smooth mattress surfaces do not. It is our clinical opinion that many of the cows that become entrapped in poorly designed stalls do so because they are lame and are struggling to get up in the stall. Many of these cows end up too far up the front end of the stall as a result of failed attempts to rise. In addition, difficulties rising mean that the lower rear limb is dragged across the stall surface, increasing hock damage. It is noticeable that many of the cows with the worst hock swellings are those that are also foot lame. We recommend that lame cows be removed from compromised mattress stalls to an area such as a well managed straw bedded pack for a recovery period once they are recognized. Diagonal lying Cows that lie diagonally deposit manure in the rear corner of the stall and contaminate the bedding material with fecal matter. Manure is transferred directly to the flank and udder. Once located diagonally across the stall, the tail is more likely to hang in the alley and potentially lead to transfer of Figure 6. Cows lying diagonally across stalls that are 15-ft head to head layout with a bob zone obstruction and a high brisket locator. 25

28 manure from the alley to the tail, to the flank, and to the rear udder (Cook, 2004). In addition, in the dug out loose bedded stall, or any stall with an unprotected curb with a sharp edge, diagonal lying is a major cause of medial hock injury (Nordlund and Cook, 2004). Diagonal lying is a complex issue caused by a variety of stall design factors involving lunge space, standing position, brisket locator design and social obstructions (Figure 6). Diagonal lying is a response by the cow to a failure to meet some or all of these requirements and we have included a flow diagram as Figure 7 to help the investigator consider the possible causes and solutions. Figure 7. A flow chart for trouble-shooting reasons for diagonal lying in free stall barns. What is the stall layout? Head to Head Against a side wall Is the stall platform at least 17 feet long? Are stalls at least 9 feet long to allow front lunging? No Yes Yes No Social Obstruction: Cows lying in the adjacent stall in front will force the cow opposite to lie diagonally across the stall and side lunge Is the brisket locator less than 5 inches high above the stall surface, with no concrete fill behind it? Yes No Cows must side lunge to rise in the stall and many will lie diagonally - unless the stall platform is extended or the side wall modified. Make sure that the upper edge of the lower divider rail is no higher than 11 inches above the stall surface. Yes Mount stall dividers on vertical posts or other type of vertical mounting and remove obstruction Is there a "bob zone" obstruction? No Is the neck rail located too close to the rear curb? Yes Allow the front limb to be thrust forward during the rising movement by lowering the height of the brisket locator and removing the concrete obstruction No Move the neck rail forward in mattress stalls to 68-70" (for first lactation heifers) and 70-72" (for mature cows) from the rear curb along the horizontal (in sand stalls, the width of the rear curb must be subtracted from this Some cows will lie diagonally across the stall when given the opportunity to side lunge! 26

29 Too often, practices such as modified or upside-down dividers, tail docking to reduce manure contamination, and unusual neckrail locations are unnecessary if we just take the time to consider the reason for the diagonal lying in the first place. BIBLIOGRAPHY Anderson N: Observations on cow comfort using 24 hour time lapse video. Proc12th Int Symp on Lameness in Ruminants, Orlando, FL, pp 12:27-34, Anderson N: Dairy cattle behavior: Cows interacting with their work place. Proc 36th Ann. Conv. Amer. Assoc. Bov. Pract. 36:10-22, Colam-Ainsworth P, Lunn GA, Thomas RC, Eddy RG: Behaviour of cows in cubicles and its possible relationship with laminitis in replacement dairy heifers. Vet Rec 125: , Cook NB: The cow comfort link to milk quality. Proc Nat Mast Council Reg Meeting, Bloomington, Minnesota, pp 19-30, Cook NB, Bennett TB, Nordlund KV: Effect of Free Stall Surface on Daily Activity Patterns in Dairy Cows with Relevance to Lameness Prevalence. J Dairy Sci 87: , Cook, NB. Concrete Brisket Slope Planning. < talls.pdf > Accessed Jan. 28, Espejo, LA, Endres, MI, and J. A. Salfer. Prevalence of Lameness in High-Producing Holstein Cows Housed in Freestall Barns in Minnesota. J Dairy Sci 89: , Galindo F, Broom DM, Jackson PGG: A note on possible link between behaviour and the occurrence of lameness in dairy cows. Applied Animal Behaviour Science 67: , Nordlund KV, Cook NB: A flowchart for evaluating dairy cow freestalls. Bovine Practitioner 37:89-96, Tucker CB: The effects of free stall surfaces and geometry on dairy cattle behavior. PhD thesis. The University of British Columbia, Tucker CB, Weary DM: Bedding on Geotextile Mattresses: How Much is Needed to Improve Cow Comfort? J Dairy Sci 87: , Tucker CB, Weary DM, Fraser D: Effects of three types of free-stall surfaces on preferences and stall usage by dairy cows. J Dairy Sci 86: , Tucker CB, Weary DM, Fraser D: Free-stall dimensions: Effects on preference and stall usage. J Dairy Sci 87: , Tucker CB, G. Zdanowicz, D M Weary. Brisket Boards Reduce Freestall Use. J Dairy Sci 89: , Wagner-Storch AM, Palmer RW, Kammel DW: Factors affecting stall use for different freestall bases. J Dairy Sci 86: , Weary DM, Taszkun I: Hock lesions and free stall design. J Dairy Sci 83: ,

30 EXTREME MAKEOVER: FREESTALL EDITION Ken Nordlund, DVM Diplomate, ABVP-Dairy Specialty University of Wisconsin-Madison, USA INTRODUCTION Despite a general appreciation that a clean dry comfortable place to lie down for dairy cows is associated with improved milk production and health, there is an understandable reluctance by dairymen to remodel existing facilities to achieve this goal. Industry recommendations for stall design and dimensions have not been consistent between consultants. Construction of partial budgets has been hampered by a lack of knowledge of the potential financial benefits that might accrue from stall improvements. However, we have started to accumulate sufficient experiences to overcome some of these barriers. This article tracks three herds over a minimum period of two years. Two barns were remodeled from mattresses to sand bedding and one barns was remodeled to improve existing mattress stalls. While each individual herd taken in isolation is merely an interesting story, the collection of these herds and others, taken together, give us insight into the actual rewards that may be realized. MATTRESS TO SAND CONVERSIONS We have shown that sand bedded freestalls allow lame cows to maintain normal patterns of stall use behavior, while mattress freestalls fail to provide a surface that results in increased standing time and reduced lying times of lame cows (Cook et al, 2004). This work has stimulated several farms to remodel their mattress freestalls to sand. In the following paragraphs, we ll review the changes in two dairies where, in 2004, stalls have been converted with simultaneous installation of a flush flume system to handle sand-laden manure. In flush flume systems, manure is scraped into an 18 inch diameter pipe while a pump pushes a recycled liquid component from a settling manure pit into the high end of the pipe. The liquid carries the sand laden manure to a settling lane, where the flow decelerates to around 1-2 feet per second along a foot long concrete settling lane. The majority of the sand settles out of the manure and is left in the lane. This washed sand is removed from the lane, allowed to drain for 2-3 weeks, and is recycled back into the stalls. The liquid component goes through a 2 or 3 stage settling process before it is used again to pump back into the system. Example Herd A Figure 1. Original mattress stalls in Herd A Herd A was expanding from 600 to 800 cows in November Existing housing consisted of a 6- year-old, 2-row tail to tail rubber crumb filled mattress barn for lactating cows and a 3-row specialneeds barn. BST use in the herd was label for mature cows throughout the follow-up period. BST was used on 28

31 approximately one third of the first lactation heifers up to March 2005, and then it was used on all heifers. The old lactating cow barn was converted by removing the mattresses and adding a 4-inch fiber glass retaining pipe bolted to the rear edge of the stall. Approximately 4-5 inches of sand were maintained on the platform and no other changes were made to the stall design. The outside walls of the special needs barn were extended to increase capacity for dry cows and post-fresh cows. Stalls in this barn were 10 feet long against the side wall, 50 inches wide, with a PVC pipe brisket locator 70 inches from the rear curb, built to accommodate 1,700 lb special needs cows. Herd performance is summarized in Table 2. Table 2. Herd performance statistics for 2 years following the change from mattresses to sand for Herd A Figure 2. A remodeled stall (left) with sand on a concrete platform and a fiber glass bedding retainer. In the special needs barn to the right, new walls are 10 feet long against the side wall to accommodate front lunge. Parameter Year 11/1/04 11/1/05 11/24/06 Difference Herd Size Turnover rate (%) Rolling Herd Avg Milk (lbs) 26,524 28,066 29,114 2,590 1 st Lactation ME305 (lbs) 28,597 31,509 31,342 2,745 Mature cow ME305 (lbs) 27,571 30,260 30,881 3,310 Annual Avg SCC ( 000/ml) Milk per cow (lbs) Rolling Avg Days-inmilk Table 3 is a completed one year partial budget for the stall changes, which cost the herd $310,000 ($403 per cow). The positive impacts assume a $13.00 milk price, 3lbs of milk per cow 29

32 per day attributed to the stalls and some improvements in SCC premium, and mastitis and lameness treatments. The financial investment was paid back within 1.5 years with an increased income of $286 per cow per year after feed costs. Table 3. Partial budget for the stall changes in herd A. POSITIVE IMPACTS COMPETING IMPACTS Increased Incomes Increased Costs 1. Improved SCC Premium from 220 to , Increased feed costs 25,262 Higher premiums at $0.03 per lb milk, 2. Improved turnover rate from 30 to 19% 84, Cost of installation of flush flume sand separation system 309, more dairy sales 3. Increase in milk production by 3lbs milk per cow per day 109, cows x 3 lbs x 365 days x $13.00 Total Increased Incomes 226,673 Total Increased Costs 334,822 Reduced Costs Reduced Incomes 1. Reduced number clinical mastitis cases 9, Improved turnover rate from 30 to 19% 25, fewer $90 per case 42 fewer cull $ Fewer lame cows treated 90 fewer cows $100 per case 9,000 Total Reduced Costs 18,720 Total Reduced Incomes 25,200 Increased Incomes + Reduced Costs = Total Positive Impacts 245,393 Increased Costs + Reduced Incomes = Total Competing Impacts 360,022 Positive Impacts minus Competing Impacts of this Project - $ 114,629 Time for Payback on Investment = 1.5 years Example Herd B Herd B was also a mattress facility milking 700 cows, with plans to expand to 1000 cows. In September 2004 they built new sand stalls Table 4. Stall dimensions in the old barn at herd B before and for first lactation after conversion to sand heifers and by March Dimensions in inches Before After 2005, they had Length, inches 96 No change removed the existing Width 47 mattresses in the old Curb to brisket locator 66 barns. Herd B went Curb to neck rail 65 one step further than Height of lower divider rail 12 Herd A and removed Height of neck rail 47 the concrete platform, Loop diameter 32 re-pouring the rear Curb height 11 curb to provide a deep sand bed. All other Surface Mattress Sand stall dimensions remained the same. The herd used Posilac at label dosage. 30

33 Herd performance data are given in Table 5 for the 2 years after the change over to sand. In the last year, the herd has added a new section to the barn and now houses over 1200 cows. Rolling herd average milk production has increased by 1,869 lbs per cow, with a 6 lb per cow per day increase. Somatic cell count has fallen slightly and rolling average DIM has increased by 21 days. Figure 3. Deep sand stalls after rennovation Table 5. Herd performance statistics for 2 years following the change from mattresses to sand for herd B Parameter Year Difference 09/01/04 09/01/05 09/01/06 Herd Size Turnover rate (%) Rolling Herd Avg Milk (lbs) 28,532 30,103 30,401 1,869 1 st Lactation ME305 (lbs) 30,232 31,701 32,662 2,430 Mature cow ME305 (lbs) 29,484 31,615 31,781 2,297 Annual Avg SCC ( 000/ml) Milk per cow (lbs) Rolling Avg Days-in-milk The changes in herd B are remarkably similar to those seen in herd A. Both were very well managed herds before the change and the improvement in cow comfort has allowed both herds to achieve more of their potential. Assuming an investment of $40 per cow for 794 cows for the stall changes and around $350,000 for the sand lanes, total expenditure was $382,000. If we assume that only half of the increase in milk, or 3 lbs per cow per day, is attributable to sand at $13.00 per cwt, minus $0.03 per lb increased feed costs yields (794 x 3 x 365) x ( ) = $86,943 extra revenue. The reduced turnover rate yielded approximately 56 more potential dairy sales at $1800-$300 = $1,500 per transaction, for a total of $84,000. Increase in income per cow was therefore $86, ,000 = $170,943 or $215 per cow. The investment will be paid back in 2.3 years. 31

34 EXPANSION OF MATTRESS STALLS WITH NO CHANGE IN SURFACE Figure 4. Mattress stalls in barn of Herd C Example Herd C This 310 cow Holstein dairy was remodeled in February Cows were housed in a 6-row mattress freestall barn with 4 pens. BST was used per label directions for all mature cows and heifers. The first lactation heifer pen was left unchanged, while each of the three mature cow pens were altered at low cost by increasing width from 44 inches to 48 inches on center and moving neck rails from 63 inches from the rear curb to 70 inches. All the work was done by the owners. In each of the three mature cow pens, the number of stalls was reduced from 74 stalls to 68 stalls (total loss of 18 stalls) and herd size was reduced to 298 cows. Eleven of the cows were sold as dairy sales. Table 7. Stall dimensions before changes were implemented in Herd C Dimension Before After Length 98 No change Width Curb to brisket locator 66 No change Curb to neck rail Height of lower divider rail 10 No change Height of neck rail 43 No change Loop diameter 32 No change Curb height 12 No change Surface Mattress No change Herd size has remained lower than previous as stocking density has been held at around 115% in most pens. Turnover rate has been reduced while rolling herd average increased by an astonishing 4,905lbs over the last 3 years, and milk / cow per day has increased by 14 lbs. 32

35 Some consultants express concern that larger stalls will become soiled and SCC problems. Once again, those concerns have not been realized, with a reduction of 94,000/ml in annual SCC. Changes in ME305 by parity have been tracked in DC305 and are shown in Figure 5. Specifically, note the difference between ME305 averages between parity groups over time. Prior to the stall enlargement, the first lactation cows averaged ~2,000 lbs more than the 3+ lactation cows. As the years pass, the first lactation cows become second lactation cows, then third lactation cows on approximately 14 month steps. As cows age in these larger stalls, their ME305 milk is closing with that of the smaller cows. Figure 5. Change in ME305 by parity before and after the stall remodel in ME Milk Production Average (lbs) Parity 1 Parity 2 Parity 3 Parity Year Herd improvements in cow comfort were associated with a reduction in new lameness case rate in herd D and allowed the hoof-trimmer to move to trimming cows twice a year. The rate of Table 8. Herd performance statistics for 3 years following the stall modification in herd C Parameter Year Difference 02/01/03 02/01/04 02/01/05 02/01/06 Herd Size Turnover rate (%) RHA Milk (lbs) 25,999 26,864 28,649 30, st Lactation ME305 (lbs) 29,042 29,701 31,858 34, Mature cow ME305 (lbs) 26,645 28,230 30,741 32, Yr Avg SCC ( 000/ml) Milk per cow (lbs) Rolling Avg DIM

36 infectious lameness (digital dermatitis) did not change, but the proportion of cows receiving hoof blocks for claw horn lesions declined to less than 5% of cows trimmed (Figure 6). SUMMARY All three herds show improvements suggesting that improvements in cow comfort pay. Investments have been recovered within the period 6 months to 3.5 years by improved milk production, lower turnover rates, higher milk quality, less lameness and an increase in the proportion of older healthier cows in the herd. For any given herd, it is impossible to predict the actual outcome of improvements in cow comfort. However, a good starting point is to compare mature cow ME305 and first lactation heifer ME305 milk production. If there is a Figure 6. Rate of infectious lesions and block treatments for claw horn lesions from hoof trimming records before and after the change in stalls and increase in preventive trimming. % Cows Trimmed /29/2002 3/29/2002 5/29/2002 7/29/2002 9/29/ /29/2002 1/29/2003 3/29/2003 %Wrap large gap between the heifers and the cows, model the potential benefits to the herd if mature cows achieve the same ME305 as the heifers over a three year period. 5/29/2003 7/29/2003 9/29/2003 %Block 11/29/2003 Date of Trim 1/29/2004 3/29/2004 5/29/2004 7/29/2004 9/29/ /29/2004 1/29/2005 3/29/2005 REFERENCE Cook NB, Bennett TB, Nordlund KV: Effect of Free Stall Surface on Daily Activity Patterns in Dairy Cows with Relevance to Lameness Prevalence. J Dairy Sci 87: ,

37 MICROENVIRONMENTS IN CALF BARNS Kenneth V. Nordlund, DVM Diplomate, ABVP-Dairy Specialty University of Wisconsin- Madison INTRODUCTION Portable air sampling devices have made it clinically feasible to evaluate air hygiene in livestock buildings. By determining the concentration of bacterial colony forming units per cubic meter of air in different areas within a barn, microenvironments of polluted air within buildings can be identified. Air sampling devices have facilitated a reconsideration of traditional assumptions about ventilation of calf barns. Both natural ventilation and mechanical ventilation using negative pressure systems are widely and successfully used in buildings used to house adult cattle. However, field investigations of herds with calf respiratory disease by our clinical service suggest that both methods are problematic for calf barns, particularly in cold weather. Barns ventilated with negative-pressure mechanical systems present their own set of practical problems. Because of the relatively small air exchange rates used in cold weather, it is difficult to design inlet systems to distribute small volumes of fresh air throughout a barn. In addition, the proper functioning of negative pressure systems is dependent upon a level of maintenance and management that is not commonly provided by calf barn personnel. In contrast, naturally ventilated calf barns present a different set of problems that include draft-free pens that prevent ventilation of the pen itself, resulting in highly polluted microenvironments within well ventilated barns. In contrast, positive-pressure ventilation systems to supplement natural or negative-pressure ventilation systems appear to be effective in overcoming these problems. This paper will review some of the basic principles of aerobiology, discuss common problems of natural and negative-pressure mechanical ventilation systems in calf barns, and describe some techniques for installing supplemental positive-pressure ventilation systems. AIRBORNE BACTERIA CONCENTRATION AS A MARKER OF AIR HYGIENE Airborne bacteria sampling devices based upon impaction on agar plates have been developed for quality control programs in sterile room manufacturing facilities, surgical suites, and other purposes. A programmed quantity of air is drawn through the sampling device at precise speeds where the mass of the airborne organism impacts the media in a Petri dish (Eduard, 1998). After incubation, the colonies are counted, allowing the user to estimate the quantity of colonyforming units per cubic meter of air (cfu/m 3 ). Because the sampling devices being manufactured are designed for very clean spaces, collections of even the minimal volumes of air frequently result in overgrown plates. In our clinical program, the standard collection through the air sampler (airideal, biomerieux, Inc., Hazelwood, MO) is 5 liters of air onto blood agar plates (BAP) where the maximum accurate count is 326,418 cfu/m 3 In the most general terms, outdoor air collected onto BAP will contain about 100-1,000 cfu/m 3, although we have collected samples as high as 20,000 in some situations. In well-ventilated livestock buildings, we expect to recover from 5,000-30,000 cfu/m 3. Generally, bacterial counts 35

38 exceed 100,000 cfu/m 3 in poorly ventilated calf housing associated with enzootic calf pneumonia. Gross observation of plates, however, suggests that many calf barns will have counts that exceed several million live organisms per cubic meter of air. There is a mixed growth of bacteria recovered on the plates, usually dominated by various Staphylococci, Streptococci, Bacillus, and E. coli. Rather than attempt to isolate and count specific respiratory pathogens, we have used the total count on BAP as a marker of air hygiene. While the total count should not be viewed as causative, a field study by Lago et al. (2006) shows an association between total cfu/m 3 and the prevalence of calves with respiratory disease. FACTORS THAT DETERMINE BACTERIAL COUNTS IN AIR A conceptual formula has been developed to describe bacterial density in air (Webster, 1984). N R C = x V ( qr + qs + qd + qv) The symbol C is the concentration of bacterial colony forming particles per cubic meter of air, N is the number of animals, V is the volume of building space, R is the release of organisms per animal, and q describes the clearance of bacteria from air by ventilation (v), sedimentation (s), inspiration into respiratory tracts (r), and desiccation and UV light (d). Stocking density is the most significant determinant of air bacterial counts. Using mathematical models to calculate airborne bacterial densities, an approximate tenfold increase in ventilation rate (example, from 4 to 40 air changes per hour) does not fully compensate for a doubling of stocking density (Webster, 1984). Airborne bacteria are released primarily from skin, feces, and bedding, but cattle with respiratory disease can exhale and cough pathogens into the air (Webster, 1984). Clearances of organisms by inspiration (q r ) into lungs and sedimentation (q s ) to the floor are minor factors. The primary clearance mechanisms are though desiccation (q d ) and ventilation (q v ). Most bacteria die within seconds after becoming airborne because of dehydration. As relative humidity increases above approximately 80%, bacterial survival time varies with species but generally increases into minutes, resulting in dramatic increases in bacterial density (Webster, 1984). Floors that allow urine and water to accumulate will be associated with higher humidity levels. Careless water-use practices from hoses and power washers can increase humidity greatly and increase the bacterial load in air. Warm air can hold more water than cold air, therefore heating air will reduce the relative humidity although the absolute water in the air remains the same. Therefore, heating air will reduce relative humidity, which may reduce bacterial loads because of increased clearance through desiccation. Ventilation removes organisms directly in the airstream leaving the building, and also reduces relative humidity which again may reduce the numbers of live airborne bacteria in the building. THE ISSUE WITH CALF HUTCHES The traditional single calf hutch remains the preferred standard for calf housing and is associated with reduced morbidity and mortality (Waltner-Toews, et al, 1986a, Waltner-Toews, et al, 1986b). Hutch housing offers several advantages for calf respiratory health including isolation and spatial separation from other calves (Callan and Garry, 2002). Unpublished data summarizing air samples collected deep inside hutches as a part of our clinical investigations 36

39 shows typical total counts of about 20,000 cfu/m 3, but will exceed 100,000 cfu/m 3 if the bedding is disturbed by an active calf. Compared with most other housing types, hutches offer the calf considerable choice to move between very different thermal environments in the rear of the hutch, front, and an outdoor pen (Brunsvold et al, 1985). However successful hutches may be for calves, they present very uncomfortable working conditions for calf caregivers in adverse weather. Delivering milk to 4 or 6 calves during a snowstorm may be viewed as a challenge, but delivery to a hundred calves is a hardship. As dairy herds in the Midwest have increased in size, there has been a renewed interest in moving calves and caregivers out of the weather and into a variety of calf barns. INDIVIDUAL CALF PENS IN NATURALLY VENTILATED BARNS Because natural ventilation systems have been successfully used in the new cow barns in expanded herds, many dairy owners have constructed naturally ventilated barns for calves as well. The barns usually have the typical open ridge and curtain sidewalls as recommended for adult cow barns (Holmes et al, 1989) and are ventilated by external wind forces and by effects of thermal buoyancy as animals warm the interior air (Albright, 1990). In warm weather, the curtain walls are lowered and the barn is ventilated by prevailing winds that move directly through the building. In cold weather, the curtain sidewalls are raised and the building is ventilated by wind entering the open eave on the windward side and potentially by thermal buoyancy of warmed air rising toward the open ridge. Figure 1. Interior view of a naturally ventilated calf barn with four rows of pens. There is a ridge opening above the translucent-panel roof to the south, adjustable curtain sidewalls, and individual calf pens surrounded by solid panels and a feeding opening in the front. The pen structure within the barns varies considerably. Some pens have three or four solid sides as shown in Figure 1, sometimes a top hover, and at the other extreme are pens with mesh panels on three or more sides as shown in Figure 2. The fully enclosed pens seem to have evolved because of concerns about drafts of cold air on young calves. Because our clinical investigations of problem herds suggested that endemic calf pneumonia is common in these new barns, we conducted a field trial to explore risk factors for calf respiratory disease in winter conditions (Lago et al, 2006). In comparing the alley and pens within barns, the airborne bacterial concentrations in the alleys were associated with the estimated barn ventilation rate, but the air hygiene within the pens was independent of barn ventilation rate. Albright (1985) indicates that incoming air from prevailing winds generally enters the barns 37

40 through eaves at too slow a speed to allow for good mixing, particularly when there are solid obstructions within the barn. Ventilation by thermal buoyancy is also limited in calf barns in winter because of the minimal difference between the interior and exterior temperatures. In the temperature data collected by Lago et al. (2006), the average temperature difference was only 1.6º C and one fourth of the barns were colder inside than outside at midday. Because both of the forces essential for natural ventilation are compromised in winter operation of calf barns, most of the pens are poorly ventilated microenvironments within well ventilated barns. Figure 2. Interior view of a naturally ventilated calf barn. The pens on the left are constructed of wire mesh panels, and the pens on the right side have been removed for cleaning. While ventilation of barns and pens is the focus of this article, the field study by Lago et al (2006) identified three factors as significantly associated with reductions in the prevalence of respiratory disease within the barns: a solid panel between each calf, sufficient bedding to nest, and lower airborne bacterial counts. The findings are summarized graphically in Figure 3. 38

41 Solid Panel between Calves The difference in prevalence of respiratory disease in pens with a wire mesh or a solid panel between each pen was substantial. A solid panel between each calf is a traditional recommendation from veterinarians and perhaps helps to limit movement of pathogens from one calf to another. However, increasing the number of solid sides was associated with higher airborne bacterial counts, a factor adverse to respiratory health. In the later part of this paper, the use of positive pressure ventilation systems to dilute and freshen the air between solid panels will be discussed. Figure 3. Graphic model of the associations between airborne bacterial concentration and prevalence of calf respiratory disease with different degrees of nesting and the presence or absence of a solid barrier between each pen. Deep nesting and presence of a solid barrier ( ); deep nesting and absence of a solid barrier ( ); moderate nesting and presence of a solid barrier ( ); moderate nesting and absence of a solid barrier ( ), minimal nesting and presence of a solid barrier ( ); and minimal nesting and absence of a solid barrier ( ). Prevalence of respiratory disease 70% 60% 50% 40% 30% 20% 10% 0% Airborne bacteria cfu/m 3 x 1000 Sufficient Bedding for the Calf to Nest With the thermoneutral zone of a newborn calf is between 10 and 26 ºC and between 0 and 23 ºC for a 1-month old calf (Wathes et al, 1983), nursing calves are very vulnerable to cold stress. In the field study by Lago et al. (2006) the average midday temperature in the barns was 3.9 C and ranged from -6.7 to 12.2 C. Overnight temperatures would be lower. Clearly, the young calves were exposed to temperatures below their thermoneutral zone during many days and nights through the period in which the trial was conducted. 39

42 Bedding provides a potentially effective mechanism for calves to Figure 4. An example of deep nesting where the reduce heat loss. If the bedding is legs of this calf are completely obscured by bedding. sufficiently deep, the calf can nest and trap a boundary layer of warm air around itself, which reduces the lower critical temperature of the calf (Webster, 1984). In our clinical work, we assign a nesting score based upon how visible the calf legs are when the calf is lying down. A score of minimal nesting is assigned when the calf lies on top of the bedding with its legs exposed. A score of moderate is assigned when calves nestle slightly into the bedding, but parts of the legs are visible above the bedding. An excellent score is assigned when the calf appears to nestle deeply with its legs completely obscured by the bedding. The potential for the calf to nest deeply appears to reduce the risk of chilling and allows for colder and better ventilated spaces. Low Total Airborne Bacterial Counts within the Pens Lower total airborne bacterial counts were associated with reduced prevalence of respiratory disease in the barns. The total airborne bacterial counts should not be viewed as the cause of respiratory disease, but rather as a marker of poorly ventilated spaces. Wathes et al. (1983) point out that most airborne bacteria are non-pathogenic, but that even dead airborne bacteria can be a burden to respiratory tract defenses. Because calves spend 100% of their time in the pens and cannot leave for even short periods of time, the exposure to the air within the microenvironment is continuous and chronic. Factors associated with lowered airborne bacterial loads include larger area pens and fewer solid sides around the pen. Increasing the area of the pen from 2.3 m 2 (25 ft 2 ) to 3.7 m 2 (40 ft 2 ) reduces the airborne bacterial density in the pen by nearly half (Lago et al, 2006). The finding that any solid panels increased the airborne bacterial counts which increases the risk of respiratory disease confounds the finding that a solid panel between each calf reduces the risk of respiratory disease. In practical terms, the expected reduction in the prevalence of respiratory disease by placing a solid panel between each calf is greater than the expected effect of the improved air hygiene without them. In our clinical work, we have emphasized the use of a solid paned between each calf, open mesh panels on the front and, if possible, rear of the pen, and use of supplemental positive pressure ventilation systems to achieve improve air hygiene between the solid panels. 40

43 REFERENCES Albright L. Natural ventilation. In: Environment control for animals and plants. St. Joseph, MI: Amer Soc Agri Eng; p Brunsvold R, Cramer C, Larsen H. Behavior of dairy calves reared in hutches as affected by temperature. Transactions of the ASAE 1985; 28(4): Callan R, Garry F. Biosecurity and bovine respiratory disease. Vet Clin North Am Food Anim Pract 2002;18: Eduard W, Heederik D. Methods for quantitative assessment of airborne levels of noninfectious microorganisms in highly contaminated work environments. Amer Industrial Hyg Assn Jour 1998; Holmes B, Bickert W, Brugger M, et al. MWPS-33 Natural Ventilating Systems for Livestock Housing. Ames, IA: Midwest Plan Service, Iowa State University; p Holmes B, Bickert W, Brugger M, et al. MWPS-32 Mechanical Ventilating Systems for Livestock Housing. Ames, IA: Midwest Plan Service, Iowa State University; p Lago A, McGuirk S, Bennett T, et al. Calf respiratory disease and pen microenvironments in naturally ventilated calf barns in winter. J Dairy Sci 2006;89: Waltner-Toews D, Martin S, Meek A. Dairy calf management, morbidity and mortality in Ontario Holstein herds. III. Association of management with morbidity. Prev Vet Med 1986;4: Waltner-Toews D, Martin S, Meek. Dairy calf management, morbidity and mortality in Ontario Holstein herds. IV. Association of management with mortality. Prev Vet Med 1986;4: Webster J. Environmental Needs. In: Calf husbandry, health and delfare. London: Collins; p Wathes C, Jones C, Webster A. Ventilation, air hygiene and animal health. Vet. Rec. 1983;113:

44 POSITIVE PRESSURE SUPPLEMENTAL VENTILATION IN CALF BARNS Kenneth V. Nordlund, DVM Diplomate, ABVP-Dairy Specialty University of Wisconsin- Madison INTRODUCTION Based upon our research showing a relationship between total airborne bacteria and the prevalence of respiratory disease, we began a serious clinical effort to use supplemental ventilation to improve air quality within individual calf pens. The following paper summarizes those experiences. NEGATIVE PRESSURE VENTILATION IN CALF BARNS IN WINTER Negative pressure mechanical ventilation systems are commonly recommended for livestock buildings because passive inlet systems are usually cheaper to construct than ductwork associated with positive pressure systems. While negative pressure systems can be very successful in many housing systems, they present special problems in calf barns. In winter, the recommended ventilation rates result in very small capacity systems that are very difficult to design and maintain. For example, MWPS guidelines suggest a minimal cold weather ventilation rate of 25 cubic meters of air per hour (m 3 /h) or 15 cubic feet per minute (ft 3 /m) per calf (Holmes et al, 1990). Some of the difficulties are best understood by working through the design parameters of an example barn housing 50 calves. A cold weather ventilation system would provide 1,275 m 3 /h (750 ft 3 /m) of fresh air to be distributed throughout the building. In order to mix with the air already in the barn, inlets should be designed so that the incoming air enters at about 4.2 meters per second (m/s) or 800 feet per minute (ft/m) (Holmes et al, 1990). To achieve this velocity, the total air inlet area would need to approximate square meters (0.93 square feet), a very small area. If the barn were configured with two rows of 25 pens on each side of a central alley, and each pen were 1.2 m (4 ft) wide, the barn might be 30 meters (100 ft) long. If a single continuous slot inlet is designed along one side of the barn, the required width of the slot would be 0.27 cm (0.009 ft) wide, or 0.14 cm ( ft) wide if it ran along both sides. Slots of this width cannot be constructed with any accuracy with standard farm building construction practices. An alternative would be to drill inlet holes into an attic to yield the appropriate area. If one inlet hole were to be drilled above each pen, each of the 100 holes would need to be just over 2.54 cm (1 inch) in diameter. More feasible, but holes this size in an attic are easily plugged with insulation, leaves, and other refuse that enters attics of livestock buildings. In addition to the difficulty of inlet sizing is the risk of other inlet openings. If there are undetected openings in the walls or around windows, air will also enter through those openings, becoming part of the cumulative inlet area, and reducing the incoming air speed. In a calf barn of this size, it would be almost impossible to not have at least a square foot of unrecognized openings. Because of these openings, the air coming into the barn usually enters too slowly to mix well and is frequently poorly distributed within the barn. Finally, if a worker should leave a door slightly ajar or break a window, the area of such an opening will essentially render the distribution system non-functional. 42

45 Clinical experience using the air sampling device during the winter has demonstrated that very poor distribution of fresh air is almost standard in negative-pressure mechanically ventilated barns. These experiences have led me to the conclusion that low-volume negative pressure systems for winter calf-barn use are not reliable enough to be recommended. POSITIVE PRESSURE SYSTEMS TO SUPPLEMENT OTHER VENTILATION SYSTEMS In contrast, positive pressure mechanical systems appear to be very dependable and consistent for low capacity situations. The advantage is that they can be a self-contained system of a fan forcing air into a distribution duct. It will not be affected by unseen cracks in the walls and windows or doors left ajar. They can complement naturally ventilated calf barns as shown in Figure 1 and deliver minimal volumes of fresh air to dilute polluted air within the pens. As weather warms, the sidewall curtains are lowered and the positive pressure system continues to operate. Positive pressure systems can also be used to complement negative pressure systems, i.e., the positive pressure system can be used at low ventilation winter situations and then be supplemented with larger capacity negative pressure systems that engage as the temperature increases. DESIGNING A POSITIVE-PRESSURE SYSTEM FOR WINTER USE The general approach to designing a positive-pressure supplemental system for winter is to 1) determine the total minimal winter ventilation rate for the building, 2) decide how many distribution ducts are required, 3) calculate the minimal cross-sectional area of the duct(s) so that it can carry the required volume of air at moderate speeds, 4) specify the area required for air to leave the duct at high speeds, and 5) distribute that air inlet area along the entire length of the duct. Minimal Ventilation Rate for Cold Calf Barns Current recommendations for a minimal winter ventilation rate in calf barns range from 25 m 3 /h (15 ft 3 /m) per calf to 4 air changes per hour of the building. If the number of calves varies from time to time, the ventilation rate should be based upon the maximal number of calves. It is often practical to calculate the ventilation capacity using both approaches and then purchase a fan to move a Figure 1. A positive pressure distribution duct installed in a naturally ventilated calf barn. The fan the powers the system is installed in an outside wall and forces air into the tube. Holes are punched at 4:00 and 8:00 o clock positions in this barn and sized so that air exits the holes at about 800 feet per minute. The very small volumes of air are driven into the pens between the solid panels. In this barn, the airborne bacterial counts in the pens dropped from 170,000 cfu/m 3 to approximately 40,000 and the annual number of calves treated for respiratory disease was reduced by approximately 75% following the installation of the supplemental system. 43