Random heterosis effects on genetic parameters, estimation of birth weight, and Kleiber ratio in a population admixture of Thailand goats

The objective of this study was to compare models for suitable genetic parameter estimation of birth weight (BWT) and Kleiber ratio (KR) in a population admixture of Thai native, Anglo-Nubian, and Saanen goats. The data set from 51 bucks and 700 does contained 3020 records of BWT and KR. Data were analyzed using five bivariate animal models with different breed effects (breed fractions of Thai native genetics (NF), breed combination groups (BCG), and genetic composition of Anglo-Nubian and Saanen). Random heterosis and dominance effects were considered when comparing models. The results indicated that accounting for breed effects as NF and BCG breed fractions of Thai native genetics and breed combination groups was not suitable and gave an incorrect ranking of animals for selection; fitting breed effect as the genetic composition of exotic breeds gave higher predictive ability. Incorporation of random heterosis effects could reduce upward bias in direct heritability, while fitting dominance slightly improved the accuracy of variance components estimates. In conclusion, the appropriate model for genetic evaluation of BWT and KR in a genetic admixture of Thai goats was fitting breed effects as the genetic composition of exotic breeds, together with random heterosis.