Pre-weaning growth of red deer calves is not determined by ability of hinds to produce milk

Abstract

Three experiments were carried out to determine whether growth of suckling red deer calves is determined by the potential of their mothers to produce milk. In the first experiment red deer hinds (n = 10, calves 6 weeks old) were treated either with bovine somatotrophin (bST, 54 mg s.c. injected every 2 weeks for 8 weeks then 108 mg every 2 weeks for a further 8 weeks) or saline. There was no effect of bST treatment on calf or hind liveweight, calf liveweight gain or body condition score of hinds. The second experiment used red and red-wapiti crossbred deer calves (n = 8–11) suckled by red deer dams that had been treated with bST or had received excipient only for 12 weeks from when the calves were 5 weeks old. Calf liveweight was affected by genotype (wapiti-red crossbreds were heavier than their red counterparts) but there was no effect of bST treatment of the hinds on calf growth in either of the genotypes. Although bST treatment of the suckled hinds elevated their plasma insulin-like growth factor-1 concentration it had no effect on milk yield. A third experiment ruled out the possibility that bST ingested by calves in milk from treated hinds would have had any influence on growth of calves in the other experiments. From these results it is concluded that the inherent demand from suckling calves, rather than the ability of adequately nourished hinds to produce milk, determines growth rate of red deer calves from birth to weaning.