Bayesian estimates of genetic parameters for reproductive traits in Nellore cows raised on pasture in the tropics

Abstract Text: We estimated (co)variances and genetic parameters for calving interval (CI), age at first calving (AFC), gestation length (GL) and days open (DO). Using multi-trait Bayesian procedures and a dataset composed of 9663, 28785, 24529 and 27944 records of AFC, CI, DO and GL, respectively, collected on Polled Nellore cows from 1977 to 2009. Heritabilities for AFC, CI, GL and DO averaged 0.36, 0.05, 0.10 and 0.04, respectively. The permanent environmental components associated with CI, GL and DO were also low, averaging 0.08, 0.07 and 0.15, respectively. The genetic correlations between AFC and CI, AFC and GL, AFC and DO, CI and GL, CI and DO and GL and DO were 0.20, 0.12, 0.11, 0.02, 0.92 and -0.21, respectively. Despite of the low heritability estimates, there is genetic variability to select the best cows and to reduce, mainly, age at first calving and calving interval.

Keywords: animal breeding, fertility, reproductive efficiency, zebu