Meta-analysis of genetic parameter estimates for reproduction, growth and carcass traits of pigs in the tropics

The design of swine breeding programs for the tropics requires knowledge of genetic parameters for economically important traits determined under tropical conditions. A literature review found a total of 468 heritability (h2) estimates, 368 genetic correlations and 254 phenotypic correlations for 35 traits across 117 peer-reviewed articles published from 1974 to 2009 and covering tropical Africa, Southeast Asia, the Caribbean and Latin America. A model that incorporated between and within study variance component was used to obtain weighted means and variances for all parameter estimates. Weighted means and standard errors of direct and maternal heritability, common litter effects and the correlation between direct and maternal effects are given for various reproduction, growth and carcass traits. The weighted means and confidence intervals for the genetic and phenotypic correlations between the trait groups are also given. Weighted least-squares analyses of the h2 estimates were performed by fitting a number of fixed effects and covariates for each trait as appropriate for the data. Breed, data origin, estimation method, data age and location of study were found to be significant (P<0.05) for majority of the traits analysed. These results indicate the relevance of having local, population-specific genetic parameter estimates for the tropics. The weighted mean estimates of genetic parameters presented here are recommended for use when reliable estimates are not available for a specific tropical pig population. This is quite appropriate because it uses the vast resource of published genetic parameter estimates effectively.