The effect of body weight at calving on milk production and reproductive performance of Friesian × Zebu heifers

ABSTRACT Twenty-six pregnant Holstein-Friesian × zebu heifers, arranged in pairs according to age, body weight, expected calving date and amount of zebu breeding, were allocated at random to two nutritional regimens during the last 12 weeks before calving. If was planned that the animals in treatment A should calve at a pre-calving live weight of 480 kg and those in treatment B should calve at 380 kg. The diet consisted of maize silage or elephant grass silage, soya-bean meal and minerals. During the first 21 days of the post-partum period both groups were given 6 kg concentrate per head daily. After this period, the feeding level was adjusted every 14 days according to the current milk yield. The mean total milk yields were 2132 kg and 1283 kg (P < 0·05) and the lengths of lactation were 239 days and 156 days (P < 0·01) for cows in treatments A and B, respectively. There was no statistically significant difference between treatments in the intervals from calving to first heat or calving to conception.