Growth and carcass fatness of ewe, wether, ram and cryptorchid crossbred lambs reared at pasture: effects of weaning age

Abstract

The effects of weaning age and sex on growth, the carcass fatness and dressing percentage were studied in grazing Dorset x (Border Leicester x Merino) lambs. Entire male (ram and cryptorchid) lambs grew significantly (P<0.001) faster from marking to slaughter than did either wethers or ewes. They were also leaner than wethers, which were in turn leaner than ewes (mean � s.e. GR tissue depth: 11.4 � 0.16, 13.9 � 0.22 and 16.3 � 0.23 mm, respectively, at a carcass weight of 19.7 kg). Across all sex groups, the GR measurement increased 1.2 � 0.03 mm per kg increase in carcass weight. An earlier weaning (at 13-15 weeks of age) reduced (P<0.001) liveweight gains. There was also a small reduction (P<0.05) in the GR measurement associated with the earlier weaning, particularly in ewe and wether lambs. The dressing percentage of wethers increased with increasing liveweight over the entire range of weights. However, in ewes and entire males, there was little change in dressing percentage with increasing liveweight above 40 kg. An earlier weaning was associated with a small reduction in dressing percentage.