Comparison of twelfth rib and rump fat thickness measurements for predicting commercial beef yield in local market carcasses

Abstract

The abilities of 12th rib and rump fat thickness measurements to predict yield of saleable beef were compared in 40 Hereford steer carcasses weighing 173-235 kg. Saleable beef yield and fat trim were significantly related (P< 0.05) to all 4 fat thickness measurements studied, rump P8, rump sacral crest, 12th rib (all cold) and 12th rib (hot). Rump measurements generally, had slightly lower standard errors of estimate than the 12th rib measurements in predicting the weights and percentages of saleable beef yield and fat trim. Rump P8 predicted saleable beef yield weight, saleable beef yield percentage, fat trim weight and fat trim percentage with means (¦ s.e.) of 72.55 (¦ 6.69) kg, 70.52 (¦ 0.72)%, 7.23 (¦ 0.86) kg and 6.99 (¦ 0.68)%, respectively. Multiple regression analysis showed that the addition of hot carcass weight or cold carcass weight as the second regressor resulted in predictions of similar accuracy. Quadratic analyses indicated that weight or percentage of cuts, manufacturing trim, saleable beef yield and fat trim were linearly related to 12th rib (cold) fat thickness and to P8 fat thickness.