Finishing steers on high grain rations. The effects of three roughages, and of urea, vitamin A, colbalt and sodium chloride supplements

A 2 x 2 x 3 x 3 split plot design was used to investigate the effects of the following treatments on the finishing of steers : cobalt supplementation-as an intraruminal cobalt oxide pellet; vitamin A supplementation-as an intramuscular injection of 2.5 x l06 i.u. ; additives to the grain-nil, 1 per cent urea, and 1 per cent urea plus 1 per cent sodium chloride ; roughage source-wheaten chaff, sorghum silage, and lucerne chaff. Ten groups each of 10 steers, of a mean (� S.E.) shrunk body-weight of 537�3.4 lb were used. One group was slaughtered before feeding the rations to measure initial carcase weight and composition. Individual steers from the other nine groups were slaughtered at 900 lb body-weight. The mean body weight gain of all steers was 2.64 � 0.05 lb per head per day, for a mean D.M, intake of 15.7 lb grain and 2.5 lb roughage over 135 � 2.2 days. Roughage sources, sodium chloride, cobalt, and the vitamin A supplement had no significant effect on performance. Steers fed lucerne, particularly with urea, exhibited mild to moderate bloating. Carcase weight gain was significantly increased by the addition of urea to the grain. Carcase weight increased from 276 � 2.2 lb in the pre-treatment group to 482 � 1.8 lb in the finished steers. The composition of this increase was 71 per cent commercial cuts of meat, 20 per cent fat trimmings and 9 per cent bone. The mean total hepatic vitamin A reserves of the unsupplemented steers at slaughter was 38 per cent of the initial reserves ; the hepatic level in 20 of these animals was less than 10 �g/g.