Genetic and phenotypic parameter estimates for reproduction traits in the Boer dam

Abstract

Variance components and further phenotypic and genetic parameters for reproduction traits including litter size at birth (LSB) and at weaning (LSW), gestation period (GP) and litter weight at birth (LWB) were estimated by use of the MTGSAM procedure fitting two-trait animal model ( y = X b + Z a a + Z P P + e ) in Boer dams. The calculations were based on 1205 parities of 435 Boer dams at Boer Goat Breeding Station in Yidu, China, during 2002–2007. Influencing factors such as parity and age of dam, kidding year and season, litter size at birth, sex of kids and some significant interactions were investigated as the fixed effects by PROC GLM (SAS8.1). The results showed that kidding year, parity and age of dam significantly influenced all the reproduction traits. Kidding season only affected the traits of GP and LWB. Litter size at birth had significant effect on LWB. The mean values of LSB, LSW, LWB and GP were 1.76 ± 0.67, 1.62 ± 0.62, 6.54 ± 2.51 kg and 151.7 ± 4.43 days. The estimates of direct additive heritability for above traits were 0.12 ± 0.01, 0.10 ± 0.01, 0.14 ± 0.02 and 0.09 ± 0.01, respectively. The estimates of all the correlations among LSB, LSW and LWB were higher than 0.52, and the genetic correlations were the highest among all the correlations. The estimates of genetic correlations between GP and other traits were medium (0.33–0.48) and lower than the permanent environmental correlations (0.60–0.72). In conclusion, compared with other goat breeds, the Boer goat has good characteristic in prolificacy. The gestation period is not significantly different in dams with increase of litter size, which is similar to the multiple birth species such as pig. However, the heritability estimates for all these reproduction traits obtained in the Boer dams are lower than 0.14; both LSB and LWB are traits with the highest heritability among 4 reproduction traits estimated. High genetic and permanent environmental correlations indicate that these traits were mainly attributable to different genetic effects or influenced by the permanent environmental effect for the different parity.