EFFECT OF VARYING PLANES OF WINTER NUTRITION OF BEEF COWS ON CALF PERFORMANCE TO WEANING

For 4 consecutive years, calf production was compared for Shorthorn cows fed at four levels during winter pregnancy and barn-nursing: (I) ad libitum corn silage plus 1.0 kg mixed hay/100 kg initial body weight daily; (II), (III) and (IV) approximately 80, 60 and 40%, respectively, of level-I intake. Half of the cows on each level received 0.45 kg linseed oilmeal (LOM) per head, daily, and half of both the LOM and no-LOM cows received supplemental vitamin A (84,000 IU per head, weekly).Neither the 4-year average birth weight (32.8, 32.3, 34.8, 32.4 kg for levels I to IV, respectively) nor the 4-year average daily gain to weaning (0.85, 0.89, 0.89, 0.89 kg for levels I to IV, respectively) were significantly different (P > 0.05). The 4-year average wither height and body depth at birth were similarly not different for the four levels. Supplementing the dam’s ration with LOM and/or vitamin A had no significant (P > 0.05) effect on either weight and body measurements at birth or gain to weaning. It was only during year 3, when level-IV cows’ (non-LOM-supplemented) daily intake was 0.033 kg digestible protein and 0.36 kg total digestible nutrients per 100 kg initial weight, that protein supplementation significantly (P < 0.05) increased birth weight and body measurements of their calves. There was little difference in survival of calves from cows fed at different levels or fed LOM versus no LOM. Contrary to expectations, vitamin A-supplemented cows appeared to produce calves with poorer survival.