Cattle reproductive performance in the Paiaguas subregion of the Brazilian Pantanal. 4. Effect of calf weaning age on breeding cows

Abstract

Effects of weaning age on reproductive performance of breeding cows were studied from 1979 to 1984 in the Brazilian Pantanal. Three hundred cows were randomly assigned to a 3 x 3 factorial. Treatments were three calf weaning ages (6,8 and 10 months) and three mineral supplements. Cows were first assigned to mineral supplementation, then, at calving, animals within each group were randomized to calf weaning age. Each group comprised 100 cows and 10 bulls. Groups were kept in three native pasture areas where groups were rotated monthly. Data were analyzed by Stepwise Multiple Regression. Calving interval was regressed on weaning age, mineral supplement, year of parturition, weight at conception, linear and quadratic effect of month of parturition and cow weight at weaning. Average calving interval was 599 t 120 days. All variables influenced (P < 0,01) calving interval, except mineral supplement. Calving rates were 62%, 61% and 55%, for weaning at 6, 8 and 10 months, respectively.