Effect of breed and some environmental factors on body weights till weaning and litter size in five goat breeds in Mexico

The aim of this study was to determine the possible effects of breed and some non-genetic factors on weights at birth (BW n = 17,857), one month of age (MW n = 14,409), weaning weight (WW n = 2629) litter size (LS n = 17,910) in five breeds of goats in Mexico. Data (n = 52,805) were collected at the National Goat Center, Tlahualilo, Durango, Mexico from the Nubian (N), Granadina (G), Saanen (S), Toggenburg (T) and Alpine (A) breeds. The model included the fixed effects of breed (BR), gender of kid (GK, 1, 2), type of birth (TB, 1, 2, 3), year of birth (YB, 1-21), season of birth (SB, 1-4) age of dam (AD, 1-10) and their interactions. Overall least square means for BW, MW, WW and LS were 3.03 ± 0.06 kg, 7.17 ± 0.08 kg, 13.2 ± 0.30 kg and 1.67 ± 0.01 kg, respectively. All the traits studied were affected (p < 0.01) by breed, year and season of birth and age of dam. The three weights studied were also significantly affected by gender and type of birth. In addition, the phenotypic expression of LS was affected (p < 0.01) by BR, YB, SB and AD. In general, neither BW nor MW were related to either AD or SB; LS was negatively correlated (p < 0.01) with both BW and WW, irrespective of genotype. The large data set provided estimates with low standard errors. Since genetic change depends not only on genetic estimations but also on the observed phenotypic variation, estimation of non-genetic-environmental factors, must be considered when building statistical models designed for estimation of genetic parameters and genetic evaluation in goats.