Effects of year, weight gain, breeding season and sex of calf on the conception rate of primiparou cows

Abstract

Data on three hundred and fourty five calvings out of primiparous Ibagé cows (5/8 Angus - 3/8 Nelore) raised in the southwest region of Rio Grande do Sul, Brazil, was collected through a fifteen-year period (1967-1970 and 1976-1986). The analysis involved the conception rate (R) and the interval from the beginning of the 2nd breeding season to the moment the cow conceived (BCI). The effects of year, calving month, sex of calf and average daily weight gain from the first breeding season to the second breeding season (ADG) were investigated. Through the least-squares methodology it was possible to determine for dams with R = 36.5% and BCI = 94.7 days, that the effects of year, calving month and ADG were significant (P < 0.01). August and September were the best calving months. Each 50 gr. over the ADG increased R by 8.7% and decreased the BCI in 6 days.