EFFECTS OF EARLY WEANING ON CALF GAIN AND COW PERFORMANCE AND INFLUENCE OF BREED, AGE OF DAM AND SEX OF CALF

Abstract

A study was conducted to determine the effects of early weaning and preconditioning to feedlot on calf gain and the effects of early weaning on cow weight and reproductive performance. A total of 390 cow-calf pairs in 1982 and 460 in 1983, representing four breed, three age-of-dam groups and two-sex-of-calf groups, were randomly assigned to either an early weaned (EW) or a late weaned (LW) group. In the fall of each year, EW calves were weaned 1 mo before LW calves and fed grain (up to 4.8 kg head−1 d−1) and hay during this period. EW calves gained approximately 0.5 kg d−1 less over the 1 mo fall test period than LW calves in 1982 (0.16 vs. 0.75 kg d−1) and 1983 (0.05 vs. 0.58 kg d−1). EW cows gained 0.32 kg d−1 more during this same period than LW cows in 1982 (0.86 vs. 0.54 kg d−1) and lost 0.21 kg d−1 less in 1983 (−0.10 vs. −0.31 kg d−1). These differences in gain did not result in significant weight differences between EW and LW cows entering the winter feeding period in either year. EW and LW cows lost a similar amount of weight over the winter feeding period in 1982–1983 (−0.13 vs. −0.12 kg d−1) and had the same weight after calving in 1983. However, during the winter feeding period of 1983–1984, EW cows lost less weight than LW cows (−0.22 vs. −0.30 kg d−1) and, thus, weighed 27.3 kg more than LW cows after calving in 1984 (468.3 vs. 441.0 kg). Weaning treatment had no effect on pregnancy rate, calf crop percentage or calving interval. Weaning treatment also had no effect on cow weight and gain, calf birth date and weight, calving interval or calf preweaning gain the following year. Interactions between weaning treatment and breed, age of dam or sex of calf were absent for most weight and weight gain parameters and for calving intervals. Calf weights were affected by breed, age of dam and sex of calf while calf gains over the fall test were affected by age of dam. Cow weights were affected by breed and age, calf crop percentage by breed and calving interval by age. Breed, age of cow and sex of calf effects for all other parameters were not significant. Key words: Beef cattle, beef calves, early weaning, preconditioning