Estimation of carcass leanness in young rams

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Abstract
The accuracy of six methods to estimate carcass leanness in young rams was studied in 36 Texel-Oxford rams, measured at 5 months of age. The rams were slaughtered and dissected. Plasma non-esterified fatty acid and very low density lipoprotein concentrations, sampled before, during and after fasting, showed no relationship with carcass leanness. The same was true for food conversion efficiency measured from 6 to 16 weeks of age, and for measurements taken with the Scanogram ultrasonic machine. The Vetscan and Danscanner ultrasonic machines gave repeatable measurements of fat depth (0·41 and 0·46 respectively). The Vetscan was the best predictor of carcass leanness by proportionally reducing the residual mean square by about 0·20, corresponding to a correlation of −0·45 between ultrasonic fat depth and carcass leanness. Inclusion of average daily gain and ultrasonic fat depth in a selection index would allow appreciable improvements in both traits.