Factors affecting body weight at birth and at 90 days of age in pure-bred and cross-bred cattle in a tropical environment

Abstract

SUMMARYLive weights of 8764 calves born in seven herds in Cuba during the years 1966–8 were measured at birth and at approximately 3 months of age. Over 2600 were pure bred: Zebu (2002), Santa Gertrudis (435) and Charolais (212); the remainder were crossbred Holstein x Zebu (4955) and Brown Swiss x Zebu (1160).Year, season of birth, herd and sex were associated with variation in mean birth weight in all breeds and crosses except Charolais in which no seasonal effect was apparent and in Brown Swiss x Zebu cross-breeds in which herd and sex effects were absent.At 90 days there was a general tendency for calves born in late spring and summer to be heavier than those bom at other times. By this age, herd variation had subsided among Brown Swiss x Zebu cross-breds, and variation due to sex had ceased to be important among Charolais calves.Estimates of heritability of birth weight ranged from 0·09 in Holstein crosses to 0·62 in Brown Swiss crosses, and of weight at 90 days from 0·05 in Brown Swiss crosses to 0·44 in the Charolais breed. Phenotypic correlations between birth and 90 days weights were of the order of + 0·25 while genetic correlations were positive for pure breeds and negative for cross-breeds.