Comparison of Linear and Threshold Models for Estimation Genetic and Phenotypic Parameters of Success of Conception at First Service and Inseminations to Conception in Holstein Cattles in East Azarbayjan Province

In this research genetic and phenotypic parameters were estimated using linear and threshold models, for reproductive traits, data from 6 large industrial dairy herd of East Azerbaijan province collected by Agriculture Jihad Organization during 10 years (2001-2010). Best linear unbiased predictions of traits breeding values were estimated using Restricted Maximum Likelihood method by WOMBAT software. Marginal posterior distributions under Bayesian approach via Gibbs sampling algorithm were estimated using repeatability analysis under animal model by Thrgibbs1f90software, in threshold model. Heritability’s of inseminations to conception and success at first insemination traits were estimated 0.078±0.014 and 0.068±0.013 respectively, in linear model and in threshold model, the means of posterior distributions of heritability’s  were estimated 0.07±0.0001 and 0.136±0.0022 respectively. The research results showed that although the amount of heritability’s for reproductive traits are low using linear and threshold models, but using threshold model in contrast with linear model cause increasing accuracy of evaluation and increasing rate of response to selection.