Department of Animal Science, Iowa State University, Ames, USA.
J Anim Sci. 2010 Apr;88(4):1220-8. doi: 10.2527/jas.2008-1755. Epub 2009 Dec 4.
The primary objective of this study was to estimate variance components and heritability of bovine respiratory disease (BRD) incidence in beef calves before weaning and during the finishing phase. The second objective was to investigate the impact of BRD incidence and treatment frequency on performance and carcass traits. Bovine respiratory disease is the biggest and most costly health challenge facing the cattle industry. The 2 populations used consisted of 1,519 preweaned calves and 3,277 head of feedlot cattle. The incidence rate of BRD in preweaned calves was 11.39%, and among treated cattle, 82.1% were treated once, 13.9% were treated twice, and 4.0% were treated 3 times or more. The incidence of BRD (P = 0.35) and the number of treatments (P = 0.77) had no significant effect on weaning BW. Heritability estimates of the entire preweaned population for BRD resistance and number of treatments were 0.11 +/- 0.06 and 0.08 +/- 0.05, respectively. The genetic correlation estimates for BRD incidence with weaning BW and birth BW were low (-0.02 +/- 0.32 and 0.07 +/- 0.27, respectively). The same estimate for the number of BRD treatments with weaning BW and birth BW was 0.25 +/- 0.35 and 0.30 +/- 0.27, respectively. The observed BRD incidence rate for feedlot cattle was observed at 9.43%. Incidence of BRD significantly (P < 0.01) decreased overall and acclimation ADG by 0.06 +/- 0.01 kg/d and 0.28 +/- 0.03 kg/d, respectively. Carcass traits were also significantly (P < 0.05) affected by BRD incidence; untreated cattle had a 9.1 +/- 1.7-kg heavier HCW. Results were similar in the analysis of treatment frequency. The heritability estimate of BRD incidence and the number of treatments were 0.07 +/- 0.04 and 0.02 +/- 0.03, respectively. Estimates of genetic correlations of BRD incidence with production traits were -0.63 +/- 0.22 for acclimation ADG, -0.04 +/- 0.23 for on-test ADG, -0.31 +/- 0.21 for overall ADG, -0.39 +/- 0.21 for final BW, -0.22 +/- 0.22 for HCW, -0.03 +/- 0.22 for LM area, 0.24 +/- 0.25 for fat, and -0.43 +/- 0.20 for marbling score. Similar results for the number of treatments and production traits were -1.00 +/- 0.68 for acclimation ADG, -0.04 +/- 0.39 for on-test ADG, -0.47 +/- 0.41 for overall ADG, -0.66 +/- 0.40 for final BW, -0.58 +/- 0.45 for HCW, -0.12 +/- 0.38 for LM area, 0.42 +/- 0.50 for fat, and -0.32 +/- 0.37 for marbling score. Because of the high economic cost associated with BRD incidence, even these modest estimates for heritability of BRD resistance should be considered for incorporation into beef cattle breeding programs.
本研究的主要目的是估计肉牛在断奶前和育肥阶段的牛呼吸道疾病（BRD）发病率的方差分量和遗传率。第二个目的是研究 BRD 发病率和治疗频率对性能和胴体性状的影响。牛呼吸道疾病是养牛业面临的最大和最昂贵的健康挑战。使用的两个群体包括 1519 头断奶前的小牛和 3277 头育肥牛。断奶前小牛的 BRD 发病率为 11.39%，在接受治疗的牛中，82.1%接受了一次治疗，13.9%接受了两次治疗，4.0%接受了三次或更多次治疗。BRD 的发病率（P=0.35）和治疗次数（P=0.77）对断奶体重无显著影响。整个断奶前群体对 BRD 抗性和治疗次数的遗传率估计值分别为 0.11±0.06 和 0.08±0.05。BRD 发病率与断奶体重和初生体重的遗传相关估计值较低（分别为-0.02±0.32 和 0.07±0.27）。BRD 治疗次数与断奶体重和初生体重的相同估计值为 0.25±0.35 和 0.30±0.27。育肥牛的观察 BRD 发病率为 9.43%。BRD 的发病率显著（P<0.01）降低了整体和适应期 ADG，分别降低了 0.06±0.01 kg/d 和 0.28±0.03 kg/d。胴体性状也受到 BRD 发病率的显著影响（P<0.05）；未治疗的牛的 HCW 重 9.1±1.7 公斤。在治疗频率的分析中也得到了类似的结果。BRD 发病率和治疗次数的遗传率估计值分别为 0.07±0.04 和 0.02±0.03。BRD 发病率与生产性状的遗传相关估计值为适应期 ADG 的-0.63±0.22，on-test ADG 的-0.04±0.23，整体 ADG 的-0.31±0.21，最终 BW 的-0.39±0.21，HCW 的-0.22±0.22，LM 面积的-0.03±0.22，脂肪的 0.24±0.25，大理石花纹评分的-0.43±0.20。治疗次数和生产性状的相似结果为适应期 ADG 的-1.00±0.68，on-test ADG 的-0.04±0.39，整体 ADG 的-0.47±0.41，最终 BW 的-0.66±0.40，HCW 的-0.58±0.45，LM 面积的-0.12±0.38，脂肪的 0.42±0.50，大理石花纹评分的-0.32±0.37。由于 BRD 发病率带来的高经济成本，即使是 BRD 抗性的这些适度遗传率估计值也应该考虑纳入肉牛育种计划。
