A comparison of live animal measurements for selecting lean beef sires

Abstract

ABSTRACTThe value of several live animal measurements for predicting carcass lean content was assessed on 97 Hereford bulls. The bulls were from a series of performance tests extending over a period of 4 years. The measurements made were live weight, ‘Weighband’ estimate of live weight, skin-fold thickness at the 13th rib, anal-fold thickness and Danscanner and Scanogram ultrasonic fat area. All measurements, except anal-fold thickness, showed satisfactory repeatability from one day to the next (0·45 to 1·00). Ultrasonic measurements showed the highest correlations with carcass lean content (0·22 to 0·66; corresponding residual s.d.'s, 13·87 and 26·46 g/kg). The most precise prediction of lean content was achieved with live weight and ultrasonic measurements in a multiple regression. The precision achieved and best anatomical sites for ultrasonic measurement varied with the group of bulls (highest R2 values 0·61 to 0·77; corresponding residual s.d. 's, 25·75 and 22·47 g/kg). The Scanogram machine produced more repeatable results than the Danscanner. When compared on the same animals Scanogram measurements gave slightly more precise prediction of carcass lean content than Danscanner measurements. Over all groups of bulls the two machines produced results of similar accuracy. Accounting for precision of estimating carcass lean content, response to selection for leanness was estimated to be 0·0034 to 0·0049 of the mean per annum for bulls of about 400 or 500 days of age.