COMPARATIVE PERFORMANCE AND DIGESTIBILITY IN DAIRY CALVES WEANED AT THREE, FIVE, AND SEVEN WEEKS OF AGE

Abstract

Ayrshire and Holstein bull calves were weaned onto dry feed at 3, 5, and 7 wk of age. Growth rates from birth to 14 wk of age, and feed intake and feed efficiency from 9 to 14 wk were not affected by weaning age. Dry matter digestibility in the week after weaning was similar for the different weaning age treatments and for the several digestion periods up to 14 wk of age. Nitrogen (N) retention was lower in the 3-wk weaned group immediately after weaning but when compared at uniform ages of 8 and 14 wk N retention was the same in the three weaning age groups. Total volatile fatty acids (VFA) in rumen fluid and proportions of acetic, propionic, and butyric acids were not affected by weaning age in the week after weaning and showed little change in proportions of individual VFA up to 14 wk, when the diet composition was constant. It was concluded that early weaning, at 3 wk of age, had little or no effect on the calf except for a slight slowing in growth during the week after weaning. Dry feed consumption increased rapidly and a relatively stable rumen fermentation developed as quickly in the calves weaned at 3 wk as in those weaned at 5 and 7 wk. In the week after weaning, dry matter and energy were digested as effectively in the early-weaned calves as in those weaned at 5 and 7 wk. Key words: Calves, weaning, digestibility, VFA