Season and parity number influence the conception rate of zebu breed cows in South-eastern Mexico

摘要

The aim of this study was to determine the effect of season of the year and parity number on conception rate of beef cows from three zebu breeds under the tropical conditions of the southeastern of Mexico. Information of 2064 calving to conception intervals (CCI) from 423 cows calving from 2006 to 2013 was used. The statistical model that described the reproductive status of the cow (conceived=1 or not conceived=0) at 90, 120, 150 and 180 days postpartum, included the effects of cow breed (Brahman, Guzerat and Nellore); year of calving (2006-2013), season of calving (dry, rainy and windy) and parity number (1 to 7). Data were analyzed to get the conception rate and odd ratios using binomial logistic regression. Overall conception rates at 90, 120, 150 and 180 days postpartum were 23.8, 37.0, 44.6 and 56.5%, respectively. Breed, parity number, season and year of calving had significant effects on conception rate. The best conception rate was for the Nellore cows followed by the Brahman and Guzerat. At 90 days postpartum, the conception rates were 48.09, 22.11 and 10.64%, whereas at 180 days the rates were 75.32, 58.21 and 37.67%, for those breeds in the same order. The worst conception rates belong to the rainy season and first parity cows. In conclusion, the overall conception rate, here obtained, was low (44.6% at 120 days postpartum) which suggest a possibility of improvement of this trait through better management that allows mating of cows in the season of better pasture availability. Breed, parity number and season were important factors that affected the conception rate. Under the conditions of this study, the Nellore cows had the highest conception rate.