Abstract
Calf records on 188 Boran and 5 grades of Simmental x Boran crossbreds were analyzed for the effect of Simmental breeding and other factors on pre- and post-weaning growth traits in Ethiopia. Crossbred calves were significantly (P < 0.05) heavier at birth than purebred Boran and birth weights increased with increasing levels of Simmental blood. Crossbred calves with 50% Simmental blood had the heaviest (P < 0.05) weight at all ages after birth. Crossing Boran cattle with Simmental breeds improved growth performances of calves up to a maximum with 50% Simmental blood. Male calves were significantly (P < 0.01) heavier at birth and at all other ages (P < 0.05) than female calves, and they grew 6.2 and 10% faster than females during pre- and post-weaning periods, respectively. Calves born in the wet season were heavier (P < 0.05) than dry-season calves at weaning age. Age of dam significantly (P < 0.05) affected pre-weaning growth rate and weaning weights of calves in a quadratic fashion. The pattern of the effect of age of dam on pre-weaning average daily gain (ADG) and weaning weights showed that 6- and 7-year-old dams had maximum positive maternal influence. Pre-weaning ADG and 6- month weaning weight of calves were positively and significantly (P < 0.01) correlated with total annual rainfall of the year of birth, in a linear fashion.
