Growth of Holstein Friesian females in the Venezuelan tropics

Abstract

ABSTRACTA study was made of the growth of Holstein Friesian females in an intensive production system in the Venezuelan tropics, using monthly weights from birth (no. = 922) up to 72 months of age (no. = 63). Birth weights were adjusted for age of dam, month and year of birth of heifer, whereas subsequent weights were adjusted for birth weight and month and year of birth. Despite lower weights at birth (mean = 35·9 kg), live weights were comparable to the Beltsville standard for the breed up to 12 months of age. However, at 24, 36, 48 and 72 months of age the weights observed only reached 0·84, 0·77, 0·75, 0·79 and 0·78, respectively, of the Beltsville standard. No effect was observed on birth weight of age of dam, month or year of birth, but birth weight affected subsequent weights (P < 0·001) and the effects of month and year of birth on live weight were significant at most ages. The poor quality of the forage consumed and stress due to high environmental temperatures and humidity appear to be the main reasons for the reduced growth rates. Von Bertalanffy's model gave a higher residual error than a polynomial model when fitted to the data, but resulted in a curve which agreed more closely with the conventional biological growth pattern.