Abstract
Birth weight (BWT), 240-day weight (WWT), and pre-weaning average daily gain (PADG) records from F1 crosses involving Charolais, Montbeliard, Limousin, and Tarentais (Bos taurus) bulls mated to Gudali and Wakwa (Bos indicus) dams were obtained from Wakwa Animal Research Station from 1970 to 1973 and analysed for genetic and environmental effects. Data were fitted to a fixed-effects model and analysed using Harvey's least-squares procedure. Both genotype and birth period significantly (P < 0.01) influenced all traits studied. Sex of calf significantly (P < 0.01) affected all traits except BWT. Charolais-sired calves were 2.8 kg heavier (P < 0.01) at birth than Limousin-sired calves. Gudali F1 calves had 0.04 kg day-1 higher PADG (P < 0.05) and 10.3 kg greater WWT (P < 0.05) than Wakwa F1 calves. Charolais- sired and Montbeliard-sired calves had similar PADG and WWT. Male calves had 0.09 kg day-1 higher PADG (P < 0.01) and 21.6 kg heavier WWT (P < 0.01) than their female contemporaries. Calves born in March and April had 0.11 kg day·1 higher PADG (P < 0.01) and 21.4 kg heavier WWT (P < 0.01) than those born in May and June. Thus, on the basis of calf growth, breeding of cows may be recommended to be restricted to the late rainy season (i.e., March-April- May).
