Understanding Nutrient & Sediment Loss at Breneman Farms - 7 Introduction Dry Matter Intake and Manure Production for Management Intensively Grazed Dairy Cattle Fall 2009 Kevan Klingberg, Dennis Frame, UW Extension/Discovery Farms/UW Madison Dennis Cosgrove, UW River Falls Figure 1. Cows on MIG grass pasture Grass-based dairies have existed in Wisconsin since we began milking cows. While many dairies have moved cattle into confinement facilities, the Wisconsin dairy industry includes an important and ever-growing group of producers who practice Management Intensive Grazing (MIG). In the past several years the interest in MIG has been increasing, as demonstrated in the 2004 Agricultural Statistics, which indicates that about 14 percent of the state s dairy operations were utilizing some version of managed grazing. Grazing systems allow producers to begin or continue dairying with minimal investment in equipment on farms where their daily activities center on managing grass and dairy animals. As with any farming system, there are many variations within rotational grazing, which include choices in the frequency of moving cattle, the types of facilities to house and milk cattle, and the method to produce milk - either conventionally or organically. The use of MIG farming systems can be done with dairy cattle, beef, sheep or any other form of livestock capable of utilizing forage-based systems. Grass-based dairy systems simultaneously combine grazing animals, actively growing pasture forage, paddock fences, watering facilities, travel lanes, and generally some type of low-cost housing facilities. These systems greatly minimize the need for mechanical forage harvesting equipment, feed storage and handling and intensive housing facilities, as well as manure storage, handling and hauling. Dairies practicing MIG report increased profitability as a Figure 2. Common paddock layout showing perimeter fences on MIG farm
result of lower feed, energy, equipment, and labor costs, as well as improved animal health and lower veterinary costs. Although Wisconsin studies have shown that when managed correctly, both grazing and non-grazing dairy systems can be profitable, a University of Wisconsin - Center for Dairy Profitability study shows that the nine year average (1999-2007) total basic costs on grazing dairies were $650 less per cow, compared to confinement dairies. Similarly, grazing dairies earned $230 more net farm income per cow compared to confinement operations over the same time period. At the heart of this farming system is a focus on ruminant livestock harvesting high quality forage via grazing and spreading their own manure in the process (Figure 1). Pastures are usually delineated by permanent perimeter fences and further subdivided by temporary fencing within the main pastures, allowing cattle controlled access to a small section of pasture at a time (Figure 2). Cattle are systematically moved into and out of paddocks, eating good quality fresh pasture, followed by a rest period that allows adequate time for the perennial grass and legume plants to re-grow before the next grazing cycle. Pastures are often connected by travel lanes, with watering systems placed in common areas that serve numerous paddocks. UW - Extension publication A3529, Pastures for profit: a guide to rotational grazing covers the basics of setting up rotational grazing (MIG) on your farm. The UW - Discovery Farms Program conducted onfarm research on the Bob and Karen Breneman farm near Rio, Wisconsin, from 2003 to 2007. The purpose of this research was to investigate environmental challenges and opportunities that grass-based dairies may have on the Wisconsin landscape. Through this project, a number of water quality studies unique to the Breneman farm were conducted. Also, while cooperating with the UW-Discovery Farms Program, pasture and dairy herd management information from this farm was compiled within a larger pool of statewide farm information through a USDA Sustainable Agriculture Research and Education (SARE) project. The Breneman farm was one of seven farms utilized for on-farm research associated with a SARE project titled: Nutrient Management Planning for Dairy Farms Practicing Management Intensive Rotational Grazing, coordinated by Dr. Dennis Cosgrove, UW - River Falls. Forage, feed, and manure considerations on grazing dairies Crop and livestock producers in Wisconsin must manage commercial fertilizers and on-farm nutrient sources (manure and rotated legume crops) for profitable crop production. Similarly, all nutrients must be carefully applied in the best form, rate, placement, and timing to minimize nitrogen (N) and phosphorus (P) entry into surface water and groundwater. To date, nutrient management planning has primarily focused on farms that mechanically apply commercial fertilizer and livestock manure to grain and forage crops grown in rotation. With reference to grazing, the NRCS Nutrient Management Standard (590) does indicate that where pasturing occurs, producers should verify that the nutrients deposited as manure within fields do not exceed the N and P requirements of the standard. The NRCS Standard for Prescribed Grazing (528) identifies grazing practices that producers should pursue for improved forage quality and quantity. Prescribed grazing practices should holistically benefit the producer, livestock, wildlife, and environment; protect water quality; improve and maintain the health of livestock, plants, and soil; and reduce soil erosion. Well- designed prescribed grazing plans identify and describe livestock, paddock and grazing management practices that the producer plans to implement to enhance environmental quality. It is important to recognize that nitrogen, phosphorus and other nutrients applied in an agricultural system Figure 3. Dairy cattle eating mixed feed delivered in the barn
continuously cycle from the soil to crops to feed to livestock to manure, and back to the soil. Dairies practicing MIG uniquely fit into this cycle as cattle are deliberately moved through a series of paddocks, eating forage plants and naturally depositing manure to the paddocks along the way. Grazing cattle spread their own manure, bypassing the need for on-farm manure storage and mechanical manure applications. Similarly, grazing cattle harvest their own forages, bypassing the need for mechanical harvesting and on-farm feed storage. While this system greatly simplifies the labor and capital requirements for dairying, it further complicates the challenge of balancing the dietary ration for producers and their livestock nutritionist. Livestock producers attempt to define, mix and deliver precise diets to animals with Figure 4. Dairy cow grazing on grass + legume pasture correct ratios of nutrients, vitamins, carbohydrates, fats and proteins, such that animals maintain enough energy to produce meat and milk. Dairy nutrition and ration balancing is a detailed process of defining specific amounts and sources of grains, forages and other dietary additives to maintain productive and profitable rates of gain and milk production. The total amount of feed (mixed recipe of ingredients) consumed daily by dairy cows is a determining factor in balancing her protein, energy, vitamin and mineral needs. Since dairy cattle consume large quantities of forage, including dry hay, haylage, corn silage, and/or fresh pasture; the intake of forage is a critical factor in balancing a ration. A balanced ration accounts for the nutrition and energy eaten by the cow via forages, and then supplements grain, protein concentrate, fats, minerals and vitamins to make up the difference. Dairy herd managers must know how much feed their cattle are consuming to properly balance rations. Dry matter intake (DMI) is a standard term used for the moisture-free amount of feed an animal eats. DMI is relatively easy to determine for animals that are offered a known quantity of feed at the barn or from a feed bunk (Figure 3). Within confinement operations, the total pounds of feed offered minus pounds of feed uneaten at the end of the day equals daily DMI. Determining DMI for rotationally grazed dairy cattle becomes more challenging because pasture condition and forage quality vary seasonally (Figure 4). Also, the actual amount of forage eaten is a function of pre-grazing pasture condition and plant material present minus post-grazing plant material remaining. The nutrient content of manure and the amount of manure generated by individual dairy cows is a function of their size, diet, feed utilization efficiency, and milk production. Similar to determining DMI for confinement dairy systems, determining manure generated within confinement dairies is relatively easy. Confined livestock Figure 5. Liquid manure from a confinement barn; stored, pumped, transported and applied to cropland
manure production can, for the most part, be measured since almost all manure is captured in gutters, feedlots, or manure storage facilities (Figure 5). Again, determining manure generated by a grazing animal is more challenging because the material is deposited naturally within paddocks as cows eat pasture forage (Figure 6). Clearly, it is important for dairy producers who practice MIG to be able to determine how much pasture forage the cows are eating each day so that a large enough paddock is offered to the cows. It is also important to have a good handle on the forage quality so that a ration can be balanced by supplementing the correct amount of additional forages, concentrates, minerals and other dietary materials, as needed. Also, within grazing dairies, knowledge of manure volume generated is a critical value necessary to make sure enough pasture land is utilized for natural manure deposition and to accurately credit manure nutrients toward pasture crop nutrient needs. Figure 6. Dairy cows on MIG pasture, eating forage and naturally depositing manure SARE study A three year on-farm research study was conducted to improve nutrient management planning and implementation on dairy farms that practice MIG. Through the study, pasture growth and quality were measured and farm information was collected from seven Wisconsin dairy farms from 2003 to 2005. The study was designed to evaluate the accuracy of four methods that MIG dairy producers use to determine dry matter intake of cows on pasture. Another goal was to refine current estimated values for daily manure production from grazing dairy cattle. Study design summary: Collect and analyze pasture forage samples for quality before and after each grazing cycle. Measure milk production during the time when cows were in each sampled paddock. Collect and analyze manure five times per farm to define average nutrient content. Gather information about amount and quality of supplemental feed in ration. Determine pasture dry matter availability before and after each grazing cycle using four different methods: 2. Plate: Use pasture plate to partially compress fresh standing plant material from a small known area. Measure plant height. Multiply plant height x farmspecific calibration of pounds of dry matter per inch of plant height. See: http://www.uwex.edu/ces/forage/wfc/ COSGROVE.html 3. Height: Measure plant height directly and multiply by a defined constant for pounds of dry matter per inch of (uncompressed) plant height. 4. Energy: Utilize a simple energy balance equation. Identify daily quantities and net energy of lactation for stored and supplemental feed eaten daily per cow. Factor cow body weight, milk production and milk composition. Utilize energy balance equation, solving for remaining DMI necessary to produce measured daily milk. Estimate daily cow manure production using feed amounts and quality, along with milk production amounts and quality. Information on total feed intake levels of P and N and total P and N excreted in milk was used to estimate manure production required to excrete the remaining ingested P and N. 1. Clipping: Clip, dry and weigh plant material from representative areas within paddocks.
SARE results Estimating DMI: Dry matter intake was estimated each day for lactating dairy cows being fed in a MIG forage system. As outlined above, four methods were used and compared to determine the accuracy and variability in estimating DMI. Each of the methods (clipping and weighing; pasture plate; pasture height; and energy balance) could realistically be done on a commercial dairy grazing farm. Table 1 shows comparative results. Table 1. Estimate of pasture forage dry matter intake by four different methods. Method 2003 2004 2005 DMI (lbs / cow / day) Clipping 12.0 +/- 4.1 26.3 +/- 6.7 15.5 +/- 8.6 Plate 13.4 +/- 3.2 27.2 +/- 6.9 16.2 +/- 5.0 Height 33.3 +/- 8.8 59.0 +/- 10.3 40.9 +/- 19.4 Of the four ways used to estimate DMI, the least reliable was measuring plant height and multiplying by a constant value for pounds of dry matter per inch of growth. Table 1 shows this method generated the highest forage production estimate each year, as well as the greatest level of variation. The estimation of available forage was significantly higher using this method than any other method. Based on stocking rates and measured milk production, this study determined that the height method overestimates forage production, thus overestimating DMI. Two of the other methods, clipping and the pasture plate, both generated similar DMI estimates when compared to each other annually. Table 1 shows the annual difference in DMI prediction between clipping and plate to be Energy 20.9 +/- 3.1 20.5 +/- 2.4 20.0 +/- 2.8 Table from Estimating Dry Matter Intake of Grazing Dairy Cattle by Cosgrove and Cooper, UWEX. approximately one pound. Yet, both clipping and plate DMI estimation methods had a high enough level of variation (+/- 3 to 8 lbs per day) that accurate ration balancing was not possible. Table 1 shows the energy balance method to have the most consistent DMI estimates with minimal variability. This three-year, seven farm study found that even though the energy method requires more information to use, it also provides the most accurate estimate of a grazing cow s actual DMI. A spread sheet was developed to estimate pasture DMI using the energy balance method: Pasture Forage Intake Calculator for Dairy Cows, http://www.uwrf. edu/grazing/dmi.xls. Estimating Manure Production: The solid feces portion of manure generated by grazing dairy cattle was estimated to be 85 pounds per cow per day. This value was mathematically determined using the seven MIG dairy herds and three years of feed ration nutrient analysis, and milk production nutrient analysis. An N and P budget was developed such that total N and P feed intake levels and total N and P output in milk was used to estimate manure production required to excrete the remaining N and P. When urine was accounted for, the total manure production increased to 120 pounds per day, which is similar to the value currently used in Wisconsin for 1,200-pound dairy cows for nutrient management planning purposes (USDA- NRCS Nutrient Management Standard - 590 and WI Conservation Planning Technical Note, 2005). Outreach Information generated from this project has been incorporated into UW - Extension Grazing Schools that train producers and agriculture professionals in Wisconsin: http://www.uwex.edu/ces/regionalwaterquality/ conservationtraining/grazing.cfm A fact sheet and associated spreadsheet has been developed by Dr. Dennis Cosgrove and Dr. Dennis Cooper, UW-Extension Specialists, UW-River Fall: 1) Estimating Dry Matter Intake of Grazing Dairy Cattle, http://www.uwex. edu/ces/crops/uwforage/gn-estimatingdmintake.pdf, and 2) Pasture Forage Intake Calculator for Dairy Cows, http:// www.uwrf.edu/grazing/dmi.xls. Wisconsin nutrient management planning software SNAP Plus has been updated to reflect the information generated from this study. SNAP Plus can be downloaded at http://www.snapplus.net/.
Conclusion Nitrogen and phosphorus cycle on livestock farms from soil to crops to feed to livestock to manure, and back to the soil. Grazing cattle spread their own manure, minimizing the need for on-farm manure storage and mechanical manure applications. Grazing cattle also harvest most of their own forages, reducing the need for mechanical harvesting and on-farm feed storage and handling. This project found that an energy balance method was the most accurate and reliable way for dairy producers who practice MIG to determine how much pasture forage the cows are eating each day (DMI). This project also confirmed that the estimated amount of daily manure produced by a 1,200-pound lactating dairy cow (120 pounds per day) is in line with current nutrient management planning guides. For more information about SARE Project LNC03-237 contact: Dr. Dennis Cosgrove, UW River Falls, Department of Plant and Earth Science, 410 S 3rd St, River Falls, WI 54022. 715-425-3745. Dennis.r.cosgrove@uwrf. edu. Project details can also be found at www.sare.org by searching for project number LNC03-237. This material is based upon work supported in part by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, Federal Administration Extension Projects, under Agreement No. 2008-45045-04386. This is the seventh of eight fact sheets developed to report on-farm research results from the Breneman farm. The Breneman farm is a grass-based MIG dairy, pasturing 80 crossbred dairy cows and supporting young stock on 200 acres of grass/legume pasture, divided into 42 paddocks (Figure 2). The farm has sandy soils, does not grow row crops, and out-winters the dairy herd on several paddocks where they are fed winter forages. Although the Breneman farm is a dairy, this information is relevant for all producers who pasture and/or out-winter livestock. On-farm water quality monitoring was conducted on the Breneman farm to measure sediment and nutrient loads in runoff water from paddocks that are used for regular rotational grazing, and are also again used to out-winter the dairy herd. Results from this on-farm research are discussed in the other fact sheets in this series. This fact sheet is part 7 of an 8-part series and can be found along with the rest of the fact sheets on the web at: www.uwdiscoveryfarms.org or by calling the UW-Discovery Farms Office at 715-983-5668. 2008 by the Board of Regents of the University of Wisconsin System. University of Wisconsin-Extension is an EEO/Affirmative Action employer and provides equal opportunities in employment and programming, including Title IX and ADA requirements. Publications are available in alternative formats upon request.