May S G, Mies W L, Edwards J W, Harris J J, Morgan J B, Garrett R P, Williams F L, Wise J W, Cross H R, Savell J W
Department of Animal Science, Texas Agricultural Experiment Station, Texas A&M University, College Station 77843-2471, USA.
J Anim Sci. 2000 May;78(5):1255-61. doi: 10.2527/2000.7851255x.
Commercial slaughter steers (n = 329) and heifers (n = 335) were selected to vary in frame size, muscle score, and carcass fat thickness to study the effectiveness of live evaluation and ultrasound as predictors of carcass composition. Three trained personnel evaluated cattle for frame size, muscle score, fat thickness, longissimus muscle area, and USDA quality and yield grade. Live and carcass real-time ultrasound measures for 12th-rib fat thickness and longissimus muscle area were taken on a subset of the cattle. At the time of slaughter, carcass ultrasound measures were taken at "chain speed." After USDA grade data were collected, one side of each carcass was fabricated into boneless primals/subprimals and trimmed to .64 cm of external fat. Simple correlation coefficients showed a moderately high positive relationship between 12th rib fat thickness and fat thickness measures obtained from live estimates (r = .70), live ultrasound (r = .81), and carcass ultrasound (r = .73). The association between estimates of longissimus muscle area and carcass longissimus muscle area were significant (P < .001) and were higher for live evaluation (r = .71) than for the ultrasonic measures (live ultrasound, r = .61; carcass ultrasound, r = .55). Three-variable regression equations, developed from the live ultrasound measures, explained 57% of the variation in percentage yield of boneless subprimals, followed by live estimates (R2 = .49) and carcass ultrasound (R2 = .31). Four-variable equations using frame size, muscle score, and selected fat thickness and weight measures explained from 43% to 66% of the variation for the percentage yield of boneless subprimals trimmed to .64 cm. Live ultrasound and(or) live estimates are viable options for assessing carcass composition before slaughter.
选择329头商业屠宰公牛和335头小母牛，使其在体格大小、肌肉评分和胴体脂肪厚度方面存在差异，以研究活体评估和超声作为胴体组成预测指标的有效性。三名经过培训的人员对牛的体格大小、肌肉评分、脂肪厚度、背最长肌面积以及美国农业部质量和产量等级进行评估。对部分牛进行了第12肋骨处脂肪厚度和背最长肌面积的活体及胴体实时超声测量。在屠宰时，以“链式速度”进行胴体超声测量。收集美国农业部等级数据后，将每具胴体的一侧加工成去骨的主要/次要切块，并将外部脂肪修剪至0.64厘米。简单相关系数显示，第12肋骨处脂肪厚度与通过活体评估（r = 0.70）、活体超声（r = 0.81）和胴体超声（r = 0.73）获得的脂肪厚度测量值之间存在中等偏高的正相关关系。背最长肌面积估计值与胴体背最长肌面积之间的关联显著（P < 0.001），且活体评估（r = 0.71）高于超声测量值（活体超声，r = 0.61；胴体超声，r = 0.55）。由活体超声测量值建立的三变量回归方程解释了去骨次要切块产量百分比变化的57%，其次是活体评估（R2 = 0.49）和胴体超声（R = 0.31）。使用体格大小、肌肉评分以及选定的脂肪厚度和体重测量值的四变量方程解释了修剪至0.64厘米的去骨次要切块产量百分比变化的43%至66%。活体超声和（或）活体评估是屠宰前评估胴体组成的可行选择。
