Heritability estimation and evaluation of genetic change resulted from selection for body weight at week eight in native chickens of Razavi Khorasan

In the present research، a number of 25،086 weight records at week eight (W8) of native chickens of Razavi Khorasan belonging to 25،086 progeny (represented 432 sires and 2937 dams) during four generations between 2006-2009 were used. In the used animal model، fixed contemporary groups of generation-hatch-sex، covariable of weight at birth (W1)، as well as direct and maternal additive genetic random effects were included. The results revealed that heritability of W8 was found to be 0. 32. Regression coefficients of W8 on W1 were estimated to be 4. 192 g and 3. 2008 g for male and female chicks، respectively which were significantly different from each other (P<0. 01). Direct and maternal additive genetic variances were 2042. 48 and 933. 92، respectively and covariance between them was found to be -936. 47. Breeding values for W8 were determined by solving Henderson''s mixed model equations. Mean change for breeding values over four generations and two sexes were not statistically significant. It could be concluded that in spite of a high heritability for W8، genetic selection for the trait has not been effective.