Effect of Plane of Nutrition on Carcass Composition and the Palatability of Pasture - Fed Lamb

Abstract

Two trials were undertaken, each with 72 grazing lambs. In trial 1, the lambs were Romney wethers and ewes with an average live weight of 27 kg and a mean initial age of 91 days. In trial 2, lambs were Southdown × Romney wethers and ewes that weighed 32 kg and had a mean initial age of 118 days. The animals were given either ad libitum or restricted postweaning access to pasture over a 6-week period, which was aimed at producing weight gain, weight maintenance or weight loss. In trials 1 and 2, respectively, the live weight changes in the gain groups were 5.6 and 6.6 kg; in the maintenance groups, the changes were 1.7 and 2.4 kg, and in the loss groups, they were —.5 and —1.5 kilograms. The gain groups lost more weight (P<.01) during transport and holding before slaughter than did the loss groups. The nutritional treatments resulted in differences in carcass composition; the carcasses from the gain group were heaviest and fattest (P<.01). However, the nutritional treatments apparently had no additional effect on carcass composition other than that normally associated with carcass weight. In the first trial, shear force values were higher (P<.01) for the loss group than for the gain group, and in both trials, the loss group had a lower (P<.01, P<.05, respectively) flavor score than the other groups. However, differences in palatability due to the fairly severe 6-week grazing treatments were small and considered to be of minor significance compared with the more important differences in carcass weight and composition.