Bergen R, Miller S P, Wilton J W, Crews D H, Mandell I B
Department of Animal and Poultry Science, University of Guelph, Ontario, N1G 2W1, Canada.
J Anim Sci. 2006 Mar;84(3):546-57. doi: 10.2527/2006.843546x.
We studied genetic relationships between age-constant live yearling beef bull growth and ultrasound traits and steer carcass traits with dissected steer carcass lean percentage adjusted to slaughter age-, HCW-, fat depth-, and marbling score-constant end points. Three measures of steer carcass lean percentage were used. Blue Tag lean percentage (BTLean) was predicted from HCW, fat depth, and LM area measurements. Ruler lean percentage (RulerLean) was predicted from carcass fat depth and LM depth and width measurements. Dissected lean percentage (DissLean) was based on dissection of the 10-11-12th rib section. Both BTLean (h2 = 0.30 to 0.44) and DissLean (h2 = 0.34 to 0.39) were more heritable than RulerLean (h2 = 0.05 to 0.14) at all end points. Genetic correlations among DissLean and RulerLean (rg = 0.61 to 0.70), DissLean and BTLean (rg = 0.56 to 0.72), and BTLean and RulerLean (rg = 0.59 to 0.90) indicated that these traits were not genetically identical. Adjusting Diss-Lean to different end points changed the magnitude, but generally not the direction, of genetic correlations with indicator traits. Ultrasound scan-age-constant live yearling bull lean percentage estimates were heritable (h2 = 0.26 to 0.42) and genetically correlated with each other (rg = 0.68 to 0.99) but had greater correlations with DissLean at slaughter age (rg = 0.24 to 0.48) and HCW (rg = 0.16 to 0.40) end points than at fat depth (rg = -0.08 to 0.13) and marbling score (rg = 0.02 to 0.11) end points. Scan-age-constant yearling bull ultrasound fat depth also had stronger correlations with DissLean at slaughter age (rg = -0.34) and HCW (rg = -0.25) than at fat depth (rg = -0.02) and marbling score (rg = -0.03) end points. Yearling bull scan-age-constant ultrasound LM area was positively correlated with DissLean at all endpoints (rg = 0.11 to 0.23). Genetic correlations between yearling bull LM method 1 width (rg = 0.38 to 0.56) and method 2 depth (rg = -0.17 to -0.38) measurements with DissLean suggested that LM shape may be a valuable addition to genetic improvement programs for carcass lean percentage at slaughter age, HCW, and fat depth constant end points. At all end points, steer carcass fat depth (rg = -0.60 to -0.64) and LM area (rg = 0.48 to 0.59) had stronger associations with DissLean than did corresponding live yearling bull measurements. Improved methods that combine live ultrasound and carcass traits would be beneficial for evaluating carcass lean percentage at fat depth or marbling score end points.
我们研究了年龄恒定的一岁育肥牛生长与超声性状之间的遗传关系，以及阉牛胴体性状与经调整至屠宰年龄、热胴体重、脂肪厚度和大理石花纹评分恒定终点的解剖阉牛胴体瘦肉率之间的遗传关系。使用了三种测量阉牛胴体瘦肉率的方法。蓝标瘦肉率（BTLean）由热胴体重、脂肪厚度和腰大肌面积测量值预测得出。直尺瘦肉率（RulerLean）由胴体脂肪厚度以及腰大肌深度和宽度测量值预测得出。解剖瘦肉率（DissLean）基于第10 - 11 - 12肋段的解剖。在所有终点处，BTLean（h2 = 0.30至0.44）和DissLean（h2 = 0.34至0.39）的遗传力均高于RulerLean（h2 = 0.05至0.14）。DissLean与RulerLean（rg = 0.61至0.70）、DissLean与BTLean（rg = 0.56至0.72）以及BTLean与RulerLean（rg = 0.59至0.90）之间的遗传相关性表明，这些性状在遗传上并非完全相同。将DissLean调整至不同终点会改变与指标性状的遗传相关性的大小，但通常不会改变其方向。超声扫描年龄恒定的一岁公牛瘦肉率估计值具有遗传力（h2 = 0.26至0.42），且相互之间存在遗传相关性（rg = 0.68至0.99），但与屠宰年龄（rg = 0.24至0.48）和热胴体重（rg = 0.16至0.40）终点处的DissLean的相关性，高于与脂肪厚度（rg = -0.08至0.13）和大理石花纹评分（rg = 0.02至0.11）终点处的DissLean的相关性。扫描年龄恒定的一岁公牛超声脂肪厚度与屠宰年龄（rg = -0.34）和热胴体重（rg = -0.25）处的DissLean的相关性，也强于与脂肪厚度（rg = -0.02）和大理石花纹评分（rg = -0.03）终点处的DissLean的相关性。一岁公牛扫描年龄恒定的超声腰大肌面积在所有终点处均与DissLean呈正相关（rg = 0.11至0.23）。一岁公牛腰大肌方法1宽度（rg = 0.38至0.56）和方法2深度（rg = -0.17至 -0.38）测量值与DissLean之间的遗传相关性表明，腰大肌形状可能是屠宰年龄、热胴体重和脂肪厚度恒定终点的胴体瘦肉率遗传改良计划中的一个有价值的补充。在所有终点处，阉牛胴体脂肪厚度（rg = -0.60至 -0.64）和腰大肌面积（rg = 0.48至0.59）与DissLean的关联，比相应的一岁活公牛测量值更强。结合活体超声和胴体性状的改进方法，将有利于评估脂肪厚度或大理石花纹评分终点处的胴体瘦肉率。
