E conomic effects of bovine

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1 The Professional Animal Scientist 27 (2011): American Registry of Professional Animal Scientists E conomic effects of bovine respiratory disease on feedlot cattle during backgrounding and finishing phases 1 K. R. Brooks,* 2,3,4 K. C. Raper,* C. E. Ward,* B. P. Holland, 5 PAS, C. R. Krehbiel, PAS, and D. L. Step *Department of Agricultural Economics; Department of Animal Science; and Veterinary Clinical Sciences, Oklahoma State University, Stillwater ABSTRACT Bovine respiratory disease (BRD) can cause significant economic losses for cattle producers. This research assessed the economic effects of BRD in backgrounding and finishing phases with assessment of calves based on serum haptoglobin (Hp). Crossbred heifers with expected high risk of BRD (n = 337) were assembled at a Kentucky order buyer facility and delivered to Stillwater, Oklahoma, in September Heifers were assigned to pens according to arrival Hp concentration: low (serum Hp <1.0 µg/ml), medium (1.0 µg/ml < serum Hp < 3.0 µg/ml), and high 1 The authors acknowledge funding support from USDA Cooperative State Research, Education and Extension Service, Hatch project H Corresponding author: kbrooks@wtamu. edu 3 Current address: Department of Agricultural Sciences, West Texas A&M University, Box 60998, Canyon Complete summary statistics on data collected can be obtained from the senior author. 5 Current address: Department of Animal and Range Sciences, South Dakota State University, Brookings (serum Hp >3.0 µg/ml). The heifers were monitored daily for signs of BRD during a 63-d backgrounding phase. After backgrounding, initial serum Hp was disregarded and heifers (n = 193) were allocated to finishing pens (5 to 7 heifers per pen) according to number of BRD treatments received: never treated (0X; n = 54), treated once (1X; n = 54), treated twice (2X; n = 34), treated 3 times (3X; n = 39), and chronically ill (CX; n = 12). Because of the limited number of pens available for the finishing phase, only 54 heifers each from the 0X and 1X categories were randomly selected for inclusion in the finishing phase. Arrival haptoglobin concentration had no significant effect on net returns (P 0.50) and was not different across number of BRD treatments (P 0.11). However, net returns decreased in the backgrounding phase (P < 0.001) and the combined backgrounding and finishing phases (P = 0.001) as number of BRD treatments increased. On average, the 0X, 1X, 2X, and 3X groups had $111.12, $92.51, $59.98, and $20.62, respectively, greater net returns than CX (P < 0.001) during backgrounding. When combining backgrounding and finishing phases, the 3X and CX groups lost $72.01 and $ more than the 0X group (P 0.03). Key words: bovine respiratory disease, cattle backgrounding, cattle feeding, haptoglobin, net returns INTRODUCTION Bovine respiratory disease (BRD) is the most common disease among feedlot cattle in the United States. It accounts for approximately 75% of feedlot morbidity and 50 to 70% of all feedlot deaths (Edwards, 1996; Galyean et al., 1999; Loneragan et al., 2001). Most BRD-related deaths occur shortly after feedlot arrival or within the first 45 d (Edwards, 1996; Loneragan et al., 2001). In fact, Buhman et al. (2000) reported approximately 91% of calves diagnosed with BRD were diagnosed within the first 27 d after arrival. Bovine respiratory disease causes an estimated $800 million to $900 million in economic losses annually to the United States beef industry from death, reduced feed efficiency, and treatment costs (Chirase and Greene, 2001). Demand for higher quality products and increased value-based marketing have heightened beef producers awareness of health management practices that may increase profit-

2 196 Brooks et al. ability and beef product quality. Feedlot producers able to purchase calves that are more likely to remain healthy during the feeding period may increase profits through reduced costs and higher revenues. Previous studies have documented the economic effect of BRD in either backgrounding or finishing programs. Knowing the economic effect of BRD on both backgrounding and finishing phases is important. Furthermore, a tool that enables producers to determine whether animals are likely to remain healthy could increase producers profits. Serum haptoglobin (Hp) concentration has been suggested as such a tool. Haptoglobin is an acutephase protein produced by the liver in response to cellular injury (Baumann and Gauldie, 1994). In cattle, Hp has been investigated as a biomarker for monitoring the response to antibiotic (Wittum et al., 1996) and discriminating between acute and chronic infection (Horadagoda et al., 1999). Berry et al. (2004) and Carter et al. (2002) found that cattle requiring treatment for BRD had higher Hp concentrations upon arrival than calves that remained healthy throughout the backgrounding phase. Using Hp concentration measured at arrival, producers could potentially determine which animals are more likely to remain healthy. The overall objective of this research was to determine the economic effects of BRD on backgrounding and finishing phases individually, as well as the 2 phases combined for the same cattle. This research also measured the effectiveness of using serum Hp concentration to predict BRD occurrence and the economic effect of multiple treatments for BRD in backgrounding on cattle feeding performance. MATERIALS AND METHODS Backgrounding Phase The current research was conducted according to an Oklahoma State University Animal Care and Use Committee approved protocol (#AG-07-14). Both phases of this experiment were conducted at the Willard Sparks Beef Research Center (Stillwater, OK). For this study, 337 crossbred heifers were purchased by Eastern Livestock order buyers, assembled at the West Kentucky Livestock Market, Marion, Kentucky, in September 2007, and transported to the experiment site. Heifers were processed after arrival on September 12 and 14 (d 0) and assigned to pens according to Hp concentration: low (serum Hp <1.0 μg/ ml), medium (1.0 μg/ml < serum Hp < 3.0 μg/ml), and high (serum Hp >3.0 μg/ml). Of the 337 heifers, 86 (25.52%) were in the low group, 98 (29.08%) were in the medium group, and 153 (45.40%) were in the high group. Heifers were fed twice daily, ad libitum, a 65% concentrate receiving growing ration during the 63-d backgrounding phase, costing $ per ton as fed. Specific details regarding rations, animal management, and experimental procedures are described by Holland et al. (2010). Heifers were evaluated daily for signs of BRD according to standard facility protocol (Step et al., 2008) in which animals were assigned a clinical attitude score (CAS; 1 4) based on depression, appetite, and respiratory signs. Personnel evaluating cattle for signs of BRD were blinded to Hp concentration group and BRD treatment history. Antimicrobial therapy was administered when CAS was 1 (mild) or 2 (moderate) and rectal temperature was 40 C or when CAS was 3 (severe) or 4 (moribund) regardless of temperature. First treatment was 10 mg of tilmicosin per kilogram of BW costing $1.0814/mL (Micotil 300, Elanco Animal Health, Greenfield, IN), second treatment was 10 mg of enrofloxacin per kilogram of BW costing $0.59/mL (Baytril 100, Bayer Animal Health, Shawnee Mission, KS), and third treatment was 2 doses of 2.2 mg of ceftiofur per kilogram of BW costing $0.50/mL (Excenel, Pharmacia & UpJohn, New York, NY), administered 48 h apart. A $0.50 chute charge was added when animals were administered treatments. After each antimicrobial treatment, calves were returned to their home pens and a hospital pen was not used. Therefore, second and third treatments were administered independent of previous treatments following the protocol described above. However, for animal welfare reasons, chronically ill animals were removed from home pens on or after d 21. Conditions necessary to be classified as chronically ill were 1) being independently assigned a BRD severity of 3, 2) receiving all 3 antimicrobial therapies according to protocol, 3) being on feed more than 21 d, and 4) experiencing a net loss of BW over the preceding 21 d on feed. For the treatment of eye infections or trauma, heifers were treated with long-acting oxytetracycline costing $0.0742/mL (Bio-Mycin 200, Boerhinger-Ingelheim, Ingelheim am Rhein, Germany). These treatments were considered independent of BRD treatments. Of the animals that died during the backgrounding phase, 2 were never treated, 4 were treated 1 time, 1 was treated 2 times, 2 were treated 3 times, and 18 were identified as chronically ill. Heifers were individually weighed on d 0, 7, 14, 21, 42, and 63. Production data included ADG during the 63-d backgrounding phase, feed intake, cost of gain (COG), vaccination costs, G:F, Hp group, number of BRD treatments, and cost of BRD treatments. Because animals were pen fed, feed intake of individual animals could not be directly measured during the backgrounding phase. Intake calculations were based on ADG and energy density of the diet using net energy equations (NRC, 2000). Feed intake for mortalities was calculated according to average feed intake per day from animals that lived times the number of days the dead animal was on the trial. Daily gain for mortalities was the last recorded weight minus initial weight divided by the number of days on trial. Backgrounding costs included vaccination costs and costs of treatment of eye or other infections. Heifers were vaccinated in the backgrounding phase against infectious bovine herpesvirus-1, bovine viral diarrhea virus (Types I and II),

3 Economic effects of bovine respiratory disease in feedlots 197 bovine parainfluenza-3, and bovine respiratory syncytial virus, costing $1.72 per calf (Pyramid 5, Fort Dodge Animal Health, Overland Park, KS), and against clostridial pathogens, costing $0.75 per calf (Vision 7 with Spur, Intervet/Schering-Plough Animal Health, De Soto, KS). Heifers were dewormed with moxidectin (5 ml/49.9 kg of BW), costing $0.055/ ml (Cydectin, Fort Dodge Animal Health), and implanted with estradiol and trenbalone acetate at $1.34 per calf (Component TE-G, Vetlife, Overland Park, KS). The initial and d-63 prices were estimated using USDA Agricultural Marketing Services feeder cattle weighted-average sale data from the Oklahoma National Stockyards (Oklahoma City, OK). Prices used were from the weeks of arrival and d 63, with adjustments for weights (KO_ LS795 for the weeks of September 12, 2007, and November 14, 2007). An ordinary least squares regression for price as a function of the number of animals sold per pen, average weight per pen, weight squared, and grade was estimated for both arrival price and d-63 price using the Agricultural Marketing Services data. Finishing Phase After the backgrounding phase (63 d), heifers were allocated to finishing pens according to the number of times they had been treated for BRD. The classification groups were never treated (0X), treated once (1X), treated twice (2X), treated 3 times (3X), and identified as chronically ill (CX). Initial classification based on arrival serum Hp was disregarded in the finishing phase. If treatment protocol was not followed in the backgrounding phase (n = 5), the animal was lame (n = 1), or the animal died during the backgrounding phase (n = 29), the animal was not included in the finishing phase. All heifers that qualified from the 2X (n = 34), 3X (n = 39), and CX (n = 12) groups were used in the finishing phase. Because a limited number of pens were available for the finishing phase, 54 heifers from each of the 0X and 1X groups were used for the finishing phase. Heifers were stratified by BW and selected using a random number generator so that a similar d-63 BW between the selected heifers and the total number of heifers in that group was maintained. Within BRD outcome group, heifers were blocked by BW (light and heavy). Nine pens were used for each of the 0X and 1X groups (n = 6 heifers/pen), 6 pens for the 2X and 3X groups (n = 5, 6, or 7 heifers/ pen), and 2 pens for the CX group (n = 6 heifers/pen). Cattle were fed according to standard procedure at the facility and weighed every 28 d. Three diets with increasing concentrate density were fed over the first 19 d until heifers adapted to the final finishing diet, costing $ per ton as fed. On d 65 and 122 of the finishing phase, LM area, fat thickness over the 12th rib, and percent intramuscular fat were estimated using ultrasound (data not shown). Using these estimates, visual appraisal, and ADG, heifers were targeted for slaughter at equal compositional endpoints. Slaughter dates were targeted for heifers within BRD treatment category and BW block, and heifers were expected to have sufficient body fat to grade US Choice and have on average 1.27-cm 12th-rib fat thickness. Heifers were slaughtered in 3 groups at the end of the feedlot phase on April 21, May 13, or May 28, 2008 (152, 174, or 189 d on feed, respectively), and slaughter dates were common for all pens in the same BRD outcome group within BW block. Because of distance and logistics involved with sample collection in a commercial abattoir, all CX group heifers were harvested on the final date (189 d on feed; Holland et al., 2010). Personnel involved in feed bunk management and slaughter date selection were not blinded to BRD treatment category. However, all heifers were managed similarly during the finishing phase except when described. Further information on finishing phase procedures and rations are outlined by Holland et al. (2010). Finishing phase production data included ADG, feed intake and cost, vaccination costs, G:F, and total days on feed. Animals that died during the finishing phase were not included in the total days on feed calculations. Feed intake in the finishing phase per animal was calculated using as-fed kilograms per day per pen divided by the number of heifers in the pen. Carcass data included marbling, YG, HCW, and fat thickness over the 12th rib. Heifers were priced on a commonly used industry grid from the commercial packing plant where they were slaughtered. Data were used to determine the effects of Hp level for BRD, treatment of sick animals, and the Hp group treatment interaction on net returns, costs, and animal performance for the backgrounding phase, finishing phase, and backgrounding and finishing phases combined. Economic Analysis Least squares means were used to analyze the performance and net return differences across Hp groups in the backgrounding phase [1] and number of BRD treatments in the finishing phase [2]: [1] [2] where Z is the independent performance measure, α and β are the parameters to be estimated; HG i is the Hp group i (i = low, medium, high), and C j is the number of BRD treatments j (j = 0, 1, 2, 3). Performance measures included ADG, G:F, feed costs, d-63 weight, and number of BRD treatments for the backgrounding phase (n = 337), finishing phase (n = 193), and the phases combined (n = 193). Carcass measures included HCW, marbling score, and YG. Net returns were analyzed for the backgrounding and finishing phases separately and for the 2 phases combined. Interaction between haptoglobin levels and number of treatments was tested in the backgrounding phase, but no significant differences were noted. Covariance was used to adjust

4 198 Brooks et al. for initial BW during the finishing phase for all performance measures; however, no significant variance was found. Confounding may still be evident because of the allocation of cattle to pens according to treatment status. Mortalities are included in net return calculations but not in physical performance measures. Final BW for cattle were taken at the feed yard on the day before slaughter and were used for finishing-phase gain calculations. Net returns were calculated for the backgrounding phase as transfer revenue/cost less purchase cost of the calves, BRD treatment costs, vaccination costs, and feed costs in the backgrounding phase. Transfer revenue/ cost is the d-63 price that was used as the revenue for the backgrounding phase and as the initial cost in the finishing phase. Processing costs varied depending on the initial BW of the animals. The net returns for the finishing phase were calculated by subtracting transfer revenue/cost, vaccination costs, and feed costs for the finishing phase from ending revenue. The total net returns was calculated by subtracting placement cost, all vaccination costs, feed costs, and BRD treatment costs from ending revenue. The transfer revenue/cost was defined as dollars per heifer at the end of the backgrounding phase and the beginning of the finishing phase. Ending revenue was dollars per heifer based on an industry pricing grid used at the slaughter facility. Estimated prices were also calculated using alternative grid premiums and discounts based on Agricultural Marketing Services data (LM_CT155) but were not found to be significantly different from the packing plant s grid prices (National Weekly Direct Slaughter Cattle Premiums and Discounts for the weeks of April 21, 2008, May 12, 2008, and May 26, 2008, respectively). The grid premiums and discounts used are included in Table 1. RESULTS AND DISCUSSION Table 2 shows the number of BRD treatments given to heifers across Hp groups. Of all BRD treatment costs, 99.7% were incurred during the 63-d backgrounding phase. Of the 337 heifers, there were a total of 113 never treated (33.53%), 98 treated once (29.08%), 42 treated twice (12.46%), 43 treated 3 times (12.76%), 12 classified as chronically ill (3.56%), and 29 mortalities (8.61%) during the backgrounding phase. During the finishing phase, 2 heifers were treated for signs of BRD. One heifer was from the 2X group and remained in her home pen throughout the duration of the finishing phase. The other heifer was in the CX group and died. Three more animals died because of digestive causes, one each from the 0X, 3X, and CX groups. Four additional heifers were not included in final statistics because of incomplete carcass data, 2 heifers each from the 2X and 3X groups. High mortality may be attributed to the use of high-risk cattle. The heifers in the study were most likely weaned immediately before transport to the auction market, where they were commingled and then shipped to the feedlot, and they appeared stressed upon arrival. Table 1. Premiums and discounts grid Item Slaughter date April 21, 2008 May 13, 2008 May 28, 2008 Choice price $ $ $ QG Prime $5.00 $5.00 $5.00 Choice $0.00 $0.00 $0.00 Select $3.00 $4.00 $5.00 Standard $25.00 $25.00 $25.00 YG 1 $3.00 $3.00 $ $1.50 $1.50 $ $0.00 $0.00 $ $25.00 $10.00 $ $25.00 $25.00 $25.00 Weight discounts, kg <250 $40.00 $40.00 $ $5.00 $5.00 $5.00 >455 $25.00 $25.00 $25.00 Other discounts Commercial $35.00 $35.00 $35.00 Utility $50.00 $50.00 $50.00 Canner $35.00 $35.00 $35.00 Dark cutter $35.00 $35.00 $35.00 Maturity stand $25.00 $25.00 $25.00 Hp Group Least squares means by Hp group are shown in Table 3. No significant differences were observed across Hp groups for any of the net returns. However, the low group had a greater (P = 0.03) marbling score than did the high group. Out of 89 heifers in the medium Hp group in the backgrounding phase, 4 heifers had negative ADG, which would have led to inflated COG; therefore, the COG for these heifers were zeroed. There was still a tendency for lower COG in the medium group compared with the high (P 0.09) and low (P 0.06) groups when these negative ADG were accounted for. Cost of BRD treatments was not different (P 0.11) across the Hp groups. Step et al. (2008) also observed Hp concentration upon arrival was unrelated to severity of the case or the need for treatment in feedlot cattle. However, Hp concentrations have been shown

5 Economic effects of bovine respiratory disease in feedlots 199 Table 2. Health outcome category of heifers across haptoglobin (Hp) groups in the backgrounding phase Hp group 1 Bovine respiratory disease (BRD) treatment group 2 0X 1X 2X 3X CX 4 Mortalities 3 Low (25.52%) Medium (29.08%) High (45.40%) Total (33.53%) (29.08%) (12.46%) (12.76%) (3.56%) (8.61%) 1 Heifers were assigned pens according to Hp concentration: low (serum Hp <1.0 μg/ml), medium (1.0 μg/ml < serum Hp < 3.0 μg/ ml), and high (serum Hp >3.0 μg/ml). 2 Groups: 0X = never treated; 1X = treated 1 time for signs of BRD; 2X = treated 2 times for signs of BRD; 3X = treated 3 times for signs of BRD; CX = classified as chronically ill. 3 Of the animals that died during the backgrounding phase, 2 were never treated, 4 were treated 1 time, 1 was treated 2 times, 2 were treated 3 times, and 18 were from the CX group. 4 Conditions necessary to be considered chronically ill were as follows: receiving all 3 antimicrobial therapies according to protocol, being on feed more than 21 d, and experiencing a net loss of BW over the preceding 21 d on feed. Total to decrease after antimicrobial treatments (Wittum et al., 1996; Carter et al., 2002; Berry et al., 2004). Berry et al. (2004) and Carter et al. (2002) observed that Hp concentration upon arrival was elevated for calves treated for BRD compared with animals that were not treated. Berry et al. (2004) showed high correlations between the number of treatments and d-0 and d-7 Hp concentrations. BRD Treatments Backgrounding Phase. Least squares means by the number of BRD treatments are shown in Table 4. Net returns in the backgrounding phase were different (P < 0.001) across all treatment groups. Heifers in the 0X, 1X, 2X, and 3X groups had $111.12, $92.51, $59.98, and $20.62, respectively, greater net returns than did the CX group (P < 0.001). Similar findings have shown calves never treated for BRD had greater returns than did calves treated once or more than once (Fulton et al., 2002). Beginning BW for cattle in the backgrounding phase was not different (P 0.51) across BRD treatments. However, BW at the end of backgrounding and the start of finishing phase were different (P < 0.001) between all treatment groups. The 3X and CX groups had lower (P < ) ADG compared with the 0X, 1X, and 2X groups. One component of the selection criteria for heifers to be grouped into the CX category was BW loss over a period of 21 d. It is possible that cattle in the 3X group could have lost weight over a period of 21 d; however, they were not removed unless they were assigned a CAS >3 by the evaluators. The CX group gained 0.98, 0.84, and 0.56 kg/d less than heifers in the 0X, 1X, and 2X groups, respectively, during the backgrounding phase (P < 0.002). Because BW loss was one factor involved in the classification of a heifer into the CX group, ADG comparisons involving the CX group may be confounded by the selection criteria. Body weight loss may be due in part to the severity and duration of the disease challenge, but other factors cannot be ruled out because there is some confounding of effects. Buhman et al. (2000) also reported sick heifer calves had reduced ADG when compared with those not sick or not removed for treatment. Other studies have also reported increased ADG for steers never treated compared with those treated once or more than once (Wittum and Perino, 1995; Gardner et al., 1999). Bovine respiratory disease treatment costs increased (P < 0.001) as the number of antimicrobial treatments increased. The 1X group averaged $9.63 per animal more than the 0X treatment group (P < 0.001), accounting for 52% of the difference in net returns. The 3X and CX groups were not different from each other (P = 0.81) but were different (P < 0.001) from the 0X group, with total BRD treatment costs more than $35 per heifer more, accounting for 39.5 and 31.8% of the difference in net returns. Bovine respiratory disease treatment has been shown to cost up to $21.70 per animal (Fulton et al., 2002). Cost of gain was greater (P < 0.001) for heifers in the 0X and 1X groups compared with the 2X, 3X, and CX groups. Finishing Phase. Net returns in the finishing phase were not different (P = 0.07) across treatment groups. This may be attributed to the fact that most of the negative effects due to health were realized in the backgrounding phase and not carried through to the finishing phase. All but one heifer (99%) treated for BRD were treated during the back-

6 200 Brooks et al. Table 3. Least squares means for production characteristics by haptoglobin group 1,2 Description Haptoglobin group Low Medium High Backgrounding phase Beginning BW, 4 kg Beginning BW, 5 kg Initial price, 4 $/heifer ADG, 4 kg/d G:F conversion BRD treatments drugs, 4,6 $/heifer Cost of feed, 4 $/heifer Cost of gain, 4,7 $/kg of gain End BW, 4 kg End price, 4 $/heifer Net returns, 4 $/heifer Finishing phase Start BW, 5 kg Start price, 5 $/heifer ADG, 5 kg/d G:F conversion Cost of feed, 5 $/heifer Cost of gain, 5 $/kg of gain Net returns, 5 $/heifer Combined phase DOF 5, Overall ADG, 5 kg/d G:F conversion Cost of gain, 5 $/kg of gain HCW, 5 kg Marbling score a ab b YG Carcass value, 5 $/heifer 1, , , Net returns, 5 $/heifer a,b Means in the same row with a different superscript letters differ (P < 0.05) 1 Mortalities are included in net return calculations but not in physical performance measures (ADG, cost of gain, or conversion). 2 Heifers were assigned to pens according to haptoglobin (Hp) concentration: low (serum Hp <1.0 μg/ml), medium (1.0 μg/ml < serum Hp < 3.0 μg/ml), and high (serum Hp >3.0 μg/ml). 3 Largest standard error of least squares means (SEM) is shown. 4 Indicates 337 heifers in backgrounding phase. 5 Indicates 193 heifers in finishing phase and overall. 6 BRD = bovine respiratory disease. 7 Out of 89 heifers in the medium group, 4 had negative ADG, which were not included in the cost of gain but were included in net returns. 8 DOF = days on feed during finishing phase (all 193 animals in combined phase were on 63-d backgrounding phase). SEM 3 grounding phase. Buhman et al. (2000) reported 91% of BRD occurrence was within the first 27 d after arrival, whereas Babcock et al. (2009) observed 74% of BRD cases occurred within the first 42 d. Although arrival BW was not different (P = 0.26) between heifers that required BRD treatment, heifers in the 3X and CX groups weighed 48 and 72 kg less, respectively, than those in the 0X group when entering the finishing phase (P < 0.001). This difference in BW is likely due to BRD effects on performance during the backgrounding phase. When calculating differences across BRD treatments, covariance was used to adjust for the differences in finishingphase initial BW, but no significant variance was found. Daily gain across BRD treatments was not different (P = 0.20) during the finishing phase. The CX heifers cost $0.48/kg of gain less than heifers in the 0X group (P = 0.01). Heifers in the 1X group did not differ (P 0.16) in COG compared with those in the 0X group with COG of $2.19/kg of gain. The CX heifers tended to have increased

7 Economic effects of bovine respiratory disease in feedlots 201 Table 4. Least squares means for production characteristics by number of bovine respiratory disease (BRD) treatments 1 Variable BRD treatment group 2 0X 1X 2X 3X CX 4 Mortalities SEM 3 Backgrounding phase Beginning BW, 5 kg Beginning BW, 6 kg Initial price, 5 $/heifer ADG, 5 kg/d 1.41 a 1.27 b 0.99 c 0.66 d 0.43 d 0.11 G:F conversion a 0.13 a 0.11 b 0.10 c 0.07 d 0.01 BRD treatments drugs, 5 $/heifer 0.00 a 9.63 b c d d e 1.34 Cost of feed, 5 $/heifer a b c d de e 5.16 Cost of gain, 5,7 $/kg of gain 1.03 a 1.19 a 2.99 b 2.54 b 3.76 b 0.80 End BW, 5 kg a b c 283 d 263 e 8.33 End price, 5 $/heifer 705 a 682 b 649 c 612 d 573 e Net returns, 5 $/heifer 8.63 a 9.98 b c d e f 5.83 Net returns relative to 0X 5, Finishing phase Start BW, 6 kg 331 a 318 b 306 c 283 d 259 e 5.16 Start price, 6 $/heifer 703 a 679 b 657 c 613 d 565 e 9.76 ADG, 6 kg/d G:F conversion a 0.11 ab 0.12 bc 0.11 bc 0.13 c 0.01 Cost of feed, 6 $/heifer a ab a b a Cost of gain, 6 $/kg of gain 2.28 a 2.19 ab 2.06 bc 1.97 c 1.80 c 0.16 Net returns, 6 $/heifer Net returns relative to 0X 6, Combined phase DOF 6, a a ab b b 6.29 Overall ADG, 6 kg/d 1.42 a 1.39 ab 1.37 ab 1.31 bc 1.19 c 0.06 G:F conversion Cost of gain, 6 $/kg of gain 1.87 a 1.92 a 1.94 ab 2.06 b 2.05 ab 0.09 HCW, 6 kg a ab ab ab b 9.28 Marbling score YG a 3.25 ab 3.10 ab 2.94 b 3.19 ab 0.28 Carcass value, 6 $/heifer 1, a 1, a 1, a 1, a 1, b Net returns, 6 $/heifer a a ab bc c Net returns relative to 0X 6, a f Means in the same row with a different superscript letters differ (P < 0.05). 1 Mortalities are included in net return calculations but not in physical performance measures (ADG, cost of gain, or conversion). 2 Groups: 0X = never treated; 1X = treated 1 time for signs of BRD; 2X = treated 2 times for signs of BRD; 3X = treated 3 times for signs of BRD; CX = classified as chronically ill. 3 Largest standard error of least squares means (SEM) is shown. 4 Conditions necessary to be considered chronically ill were as follows: receiving all 3 antimicrobial therapies according to protocol, being on feed more than 21 d, and experiencing a net loss of BW over the preceding 21 d on feed. 5 Indicates 337 heifers in backgrounding phase. 6 Indicates 193 heifers in finishing phase and overall. 7 Out of 89 heifers, 4 had negative ADG in the backgrounding phase, which were not included in the cost of gain but were included in net returns. 8 Net returns relative to the 0X treatment group, $/heifer, based on least squares means. 9 DOF = days on feed during finishing phase (all 193 animals in combined phase were on 63-d backgrounding phase). G:F during the finishing phase. Lower rate of gain during the backgrounding phase by CX heifers likely resulted in a compensatory response during finishing. Similar responses have been shown when growing-phase ADG has been altered by dietary energy concentration (Sainz et al., 1995) or winter forage quality (Hersom et al., 2004). However, CX heifers had (P = 0.02) lower HCW than did 0X heifers ( and kg, respectively).

8 202 Brooks et al. Figure 1. Net returns ($/heifer) in backgrounding (P < 0.001), finishing (P = 0.07), and combined backgrounding and finishing (P = 0.001) phases for heifers not treated (0X) or treated once (1X), twice (2X), or thrice (3X) for signs of bovine respiratory disease or classified as chronically ill (CX) during the backgrounding phase. There were no differences (P = 0.30) across treatment groups for marbling score. The 3X group had lower (P = 0.05) YG compared with the 0X group (2.94 and 3.35, respectively). Backgrounding and Finishing Phases Combined. In combining the backgrounding and finishing phases, there were significant differences (P 0.03) between the 3X and CX groups compared with the 0X group for net returns. Figure 1 shows net returns across the number of BRD treatments for all 3 phases. Heifers in the 3X and CX groups lost $72.01 and $ more than those in the 0X group when combining phases. Most of the loss was during the backgrounding phase, when CX heifers lost $ more compared with 0X heifers, with 32% of this difference being attributed to BRD treatment costs. There were no significant differences between heifers in the 1X and 2X groups when combing the backgrounding and finishing phases. Previous research showed calves treated more than once decreased net returns (Edwards, 1996; Fulton et al., 2002). No differences (P 0.327) were observed for days on feed in the finishing phase among the 0X, 1X, and 2X groups. The 3X and CX heifers were on feed at least 13 d longer than those in the 0X group (P = 0.01 and P = 0.05, respectively). All CX-group heifers were slaughtered on the final date (189 d on feed). Daily gain, when combining backgrounding and finishing phases, was different (P = 0.001) between the 0X and CX groups (1.42 and 1.19 kg/d, respectively). Buhman et al. (2000) reported sick calves to have lower ADG in the first 62 d after arrival compared with those never treated, and the reduction in ADG continued throughout the remainder of the feedlot period. During the backgrounding phase in the current study, differences in ADG among the 0X, 1X, and 2X groups were observed, but no differences were observed during finishing phase or when phases were combined. Most of the BRD incidence occurred during the backgrounding phase. When viewing both phases together as a single growing finishing system, it is evident that animals treated for signs of BRD had reduced performance during the time of the disease challenge. During the finishing phase, after recovering, 1X and 2X cattle were able to compensate and regain, respectively, the 14- and 29-kg disadvantage in BW observed at the beginning of the finishing phase, and only 13 to 21 d were required for 3X cattle to regain the 70-kg disadvantage in BW. An increase in ADG by cattle previously treated for BRD versus nontreated animals has been observed previously (Snowder et al., 2006; Montgomery et al., 2009). In addition, Babcock et al. (2009) reported that BRD observed in lighter calves, with increased days on feed after treatment before slaughter, did not have as great an effect Figure 2. Cost of gain ($/kg of gain) in backgrounding (P < 0.001), finishing (P = 0.03), and combined backgrounding and finishing (P = 0.06) phases for heifers not treated (0X) or treated once (1X), twice (2X), or thrice (3X) for signs of bovine respiratory disease or classified as chronically ill (CX) during the backgrounding phase.

9 Economic effects of bovine respiratory disease in feedlots 203 on finishing performance and carcass characteristics as that observed in heavier cattle that were treated closer to slaughter. Figure 2 shows the COG across the number of BRD treatments for all 3 phases. During the backgrounding phase, there were significant differences between COG for 0X and 1X heifers and COG for 2X, 3X, and CX heifers (P < 0.05). The difference between 0X and CX was more than $2.73/kg of gain. The 0X heifers still had a different COG (P < 0.03) from that of 3X and CX heifers during the finishing phase; however, the 0X group was more than $0.31/kg of gain compared with the 3X and CX groups. Once both phases were combined, only slight differences in COG were observed. One of the main costs in the backgrounding phase is BRD treatment. When these costs are distributed across the combined phases, the increased gain offsets the effect from BRD treatment costs. Although 3X and CX heifers in the current study were able to achieve similar final live and carcass weights and carcass traits to those heifers never requiring treatment, or requiring only 1 or 2 treatments, for signs of BRD, they still exhibited lower overall net returns. Those heifers in the 3X and CX treatment groups required longer days on feed, which resulted in increased feed and yardage costs. IMPLICATIONS The present study showed serum Hp concentration upon arrival to the feedlot was not an effective predictor of BRD incidence in a backgrounding phase. Bovine respiratory disease groups, based on serum Hp concentrations, had no effect on net returns. Further studies should be conducted to target management strategies for heifers that have increased risk of health problems. Further research should be conducted to identify possible cutoff values for Hp levels in predicting BRD outbreaks in heifers. Heifers in the 3X and CX groups were able to produce carcasses with similar values to those never treated or treated once or twice. Future research should be conducted to determine from an economic standpoint whether to sell all cattle on a pen average or to sort those animals with multiple treatments and hold them longer in hopes that the carcass value will overcome the extra cost. LITERATURE CITED Babcock, A. H., B. J. White, S. S. Dritz, D. U. Thomson, and D. G. Renter Feedlot health and performance effects associated with the timing of respiratory disease treatment. J. Anim. Sci. 87:314. Baumann, H., and J. Gauldie The acute phase response. Immunol. Today 15:74. Berry, B. A., A. W. Confer, C. R. Krehbiel, D. R. Gill, R. A. Smith, and M. Montelongo Effects of dietary energy and starch concentrations for newly received feedlot calves: II. Acute-phase protein response. J. Anim. Sci. 82:845. Buhman, M. J., L. J. Perino, M. L. Galyean, T. E. Wittum, T. H. Montgomery, and R. S. 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