Study of genetic, phenotypic and environment trends for growth traits in Shal sheep

In this study records of 6221, 4261, 3112, 2240 and 2370 related to the birth weight (BW), weaning weight (WW), 6-month weight (6MW), 9-month weight (9MW) and yearling weight (YW) were collected by Qazvin Jahad-e-Keshavarzi organization during 1998 to 2009, were used to estimate genetic parameters, genetic progress, phenotypic, genetic and environmental trends. (Co) variance components and genetic parameters were estimated with different models which including direct genetic effects, with and without maternal additive genetic as well as maternal permanent environmental effects, using restricted maximum likelihood (REML) method. The most appropriate model for each trait was determined based on likelihood ratio tests. Best Liner Unbiased Prediction (BLUP) of breeding values and genetic and phenotypic trends of the traits were estimated as the regression of average predicted breeding values and phenotypic values over birth years, respectively. Environmental trends were assessed as the difference between phenotypic and genetic trends. Mixed model methodology based on a multivariate animal model was used for prediction of breeding value. Estimated direct heritability obtained from the most appropriate model were 0.13±0.03, 0.29±0.04, 0.16±0.03, 0.31±0.03 and 0.19±0.02 for BW, WW, 6MW, 9MW and YW, respectively. Total genetic progress after 10 years for BW, WW, 6MW, 9MW and YW were 69, 593, 329, 364 and 417 g, respectively. Genetic trend for BW, WW, 6MW, 9MW and 12W were 6.3±1, 56.2±8, 31.5±8, 39.1±2 and 42.9±4 g per year, respectively, and phenotypic trends for traits were -68.7±4, - 42.1±6, 59.6±2, 65.4±5 and 131.7±10 g per year, correspondingly.