The effects of castration and of the poll gene on prime lamb production

Abstract

During 1961 and 1962 experiments were conducted at Tamworth Agricultural Research Station to evaluate the effect of several castration treatments and of the poll gene on prime lamb production. Ram lambs and lambs sterilized by removal of the cauda epididymis had significantly heavier live weights at 16 weeks of age than did partially castrated lambs (half of each testis removed). These in turn were significantly heavier than wethers and ewes. Among single lambs, rams and sterilized rams had carcasses that were nine per cent heavier than those of wether and ewe lambs (P<0.01). With twins this difference was reduced to 1.3 per cent for wethers (n.s.) and eight per cent for ewes (P<0.05). The average carcass weight of partially castrated lambs was between these two groups. Mean horn volumes and preputial adhesion scores suggested that these lambs had less endogenous androgen than rams and sterilized lambs. All single lamb carcasses were classed as First Grade. There were no significant differences in the number of twin lambs that were down-graded in each treatment. Fifty-four per cent of the ram and sterilized ram carcasses were classed as Ram and would be subject to a price penalty regardless of their carcass grade. Taste panel tests of meat from the hind legs of wether and sterilized ram carcasses showed that the sterilized ram meat was slightly more acceptable. There were no significant differences in live weight, carcass weight or carcass grade between polled and horned lambs.