Comparison of different models for estimation of heritability and genetic and phenotypic trends of some economic traits in Yazd native fowl

The objective of the present study was to estimate variance components and the heritability for economic traits in Yazd native fowl and evaluation of performed breeding programs based on genetic and phenotypic trends according to the most suitable model for each trait. For this purpose، the information of 9000 female and 9000 male birds collected during 2001 to 2008 were used. Variance components were estimated for body weight at 8 (BW8) and 12 (BW12) weeks of age، age at sexual maturity (ASM)، egg number (EN) and average egg weight at 28th، 30th and 32nd weeks (EW) using restricted maximum likelihood method and six animal models. The most suitable model was determined using likelihood ratio test for each trait. For BW8، BW12، ASM and EN، a model consisting of maternal permanent environmental effect in addition to direct genetic effect was the best. For egg weight، a model with maternal genetic and permanent environmental effects in addition to direct genetic effect was the optimal model. The estimates of direct heritability were from 0. 11 (EN) to 0. 17 (ASM). The results indicated that ignoring maternal effects in the models، overestimates the estimating of direct genetic variance and heritability for all traits. The genetic trends were calculated for BW8، BW12، ASM، EN and EW (2. 96 and 4. 86 g، -0. 02 day، 0. 02 egg number and 0. 01 g، respectively). Maternal genetic trend for EW (-0. 01) was significant (P<0. 001). The results indicated that performed breeding program during generations was favorable for BW8 and BW12