Genetic Evaluation And Studies On Growth Traits Of Chinese Simmental

Seven traits including growth traits and reproduction traits were analyzed by genetic and statistical methods in this study. The data were collected from six national Chinese Simmental farms in 1980-2000. Genetic parameters were estimated by animal models and MTDFREML. The estimated heritabilities of the seven traits:birth,weaning,yearling,18-month weight,mature cow weight,gestation length,calving date,were 0.32,0.11,0.27,0.36,0.47,0.10,and 0.07 respectively.Direct-maternal genetic correlations of growth traits were negative and high,from -0.39 to -0.99. Direct genetic correlations were higher between two close growth traits than between two far growth traits. The direct and maternal additive genetic correlations between yearling weight and 18-month weight,mature cow weight were high,showing yearling weight is good as a early select criterion.The correlations between direct additive genetic effects of growth traits and gestation length were low,from -0.09 to 0.05. The correlations between maternal additive genetic effects of growth traits and gestation length were almost moderate or more and positive,identifying longer gestation length,larger maternal effects. The correlation values between direct additive genetic effects of growth traits and calving date were from -0.38 to 0.05,implying that the prolonging of dam' s calving date would reduce the growth performance of calves. The correlation values between maternal additive genetic effects of growth traits and calving date were from 0.01 to 0.20.Significant influences of herd and sire on almost all growth traits were found;birth-year significantly affected all growth traits except that of mature cow weight;birth-season had apparent influences on weaning and yearling weight;age of dam had significant influences on birth,weaning weight,sex significantly affected birth,weaning,and 18-month weight.