Hamlin K E, Green R D, Perkins T L, Cundiff L V, Miller M F
Department of Animal Science and Food Technology, Texas Tech University, Lubbock 79409-2141, USA.
J Anim Sci. 1995 Jun;73(6):1713-24. doi: 10.2527/1995.7361713x.
Serial ultrasonic measures of fat thickness (FTU) and longissimus muscle area (LMU) were taken on 180 feedlot steers representing 11 sire-breed groups at two 60-d intervals. Cattle then were slaughtered in four groups of 45 at 21-d intervals with ultrasonic measures taken at each interval. Analyses of variance indicated weight (WT) effects (P < .001) for all FTU measures and many of the LMU measures. Age was a source of variation (P < .05) for FTU and LMU over the first five measurement dates. Sire-breed (SBD) effects (P < .001) were prevalent for all FTU estimates and early LMU predictions. Some dam line and SBD x dam line interactions were detected (P < .1) for the FTU and LMU estimates. Age effects were described quadratically (P < .001) when FTU and LMU were regressed on age (R2 = 47 and 68%, respectively). When FTU and LMU were regressed on WT, effects were described quadratically (P < .001) with R2 values of 46 and 72%, respectively. Animals then were assigned to one of four biological types (BT) based on percentage of retail product (0-mm fat trim) using discriminant cluster analysis. Within BT, ultrasonic variables were regressed on age. Quadratic effects (P < .01) were detected for both FTU and LMU. Weight also contributed to variation observed in both ultrasonically measured variables for all BT (P < .001). These data indicate that changes in fat and muscle size as affected by age and weight are detectable using serially collected ultrasound measures. Furthermore, the age and weight relationships of predicted FTA and LMA varied across the four biological types. This suggests a need for derivation of biological type-specific age and(or) weight adjustment equations for cattle evaluation purposes.
在两个60天的间隔期，对代表11个父本品种组的180头育肥牛进行了脂肪厚度（FTU）和背最长肌面积（LMU）的连续超声测量。然后，将牛分为四组，每组45头，每隔21天屠宰一组，并在每个间隔期进行超声测量。方差分析表明，所有FTU测量值和许多LMU测量值都存在体重（WT）效应（P < .001）。在前五个测量日期，年龄是FTU和LMU变化的一个来源（P < .05）。所有FTU估计值和早期LMU预测值都普遍存在父本品种（SBD）效应（P < .001）。在FTU和LMU估计值中，检测到了一些母系和SBD×母系的相互作用（P < .1）。当FTU和LMU与年龄进行回归时，年龄效应呈二次曲线关系（P < .001）（R2分别为47%和68%）。当FTU和LMU与WT进行回归时，效应呈二次曲线关系（P < .001），R2值分别为46%和72%。然后，使用判别聚类分析，根据零售产品百分比（0毫米脂肪修剪）将动物分为四种生物学类型（BT）之一。在每种BT内，将超声变量与年龄进行回归。FTU和LMU均检测到二次效应（P < .01）。体重也导致了所有BT的两个超声测量变量中观察到的变化（P < .001）。这些数据表明，使用连续收集的超声测量可以检测到年龄和体重对脂肪和肌肉大小的影响。此外，预测的FTA和LMA的年龄和体重关系在四种生物学类型中各不相同。这表明需要为牛的评估目的推导特定生物学类型的年龄和（或）体重调整方程。
