Developmental growth and body weight loss of cattle. 1. Experimental design, body weight growth, and the effects of developmental growth and body weight loss on the dressed carcass and the offal
Austral. J. Agric. Res 18: 1015-1031
Of 20 Aberdeen-Angus bullocks of mean weight 214 kg individually fed to achieve a daily growth rate of 1 kg 2 were killed at 250, 281, 316, 356 or 400 kg. Growth in other pairs was continued to 15% above each of these weights, then allowed to drop 0.5 kg daily to return to these weights, when the bullocks were killed. The ration during the growth phase was mainly of pellets with 16.5% crude protein and during the period of weight loss it was of oat straw with 1.9% crude protein. Carcass yield increased with increasing liveweight. The relative growth rates of hide, feet and head were less than that of liveweight. Adjusted mean weights of feet, head and tail were greater in the cattle grown to heavier weight then reduced than in those killed immediately on achieving the required weight. In the cattle killed immediately the relative growth rates of liver, gall bladder, heart, lungs, kidneys and gut tissue were less than that of liveweight, although changes in weights of spleen and blood were similar to that in liveweight. The difference between cattle killed immediately and those reduced in adjusted mean weight were significant for all components except heart, lungs and abdominal fat.