Estimation of genetic trends and parameters for some economic traits using different linear models in Mazandaran native chickens

At the Mazandaran native fowl breeding center we have developed a breeding scheme in order to produce dual purpose birds for rural areas. In this way, fully pedigreed records were applied to estimate variance components of some economic traits in a population of Mazandaran native fowl. The number of animals in the pedigree programme were 74351 and the number of records in data were 47452 to 72547. In the present study direct and maternal genetic and maternal common environmental effects were estimated for some economic traits including body weight at day 1 of age (BW1), body weight at 8 weeks of age (BW8), body weight at 12 weeks of age (BW12), weight at sexual maturity (WSM), age at sexual maturity (ASM), egg number (EN), egg weight at day 1 of laying (EW1) and mean egg weight (MEW). Data analysis was conducted by a series of six various animal models accompanied by maternal effects for the above-mentioned traits. Estimates of direct heritability ranged from 0.04 (BWI) to 0.54 (MEW) on the basis of most best fitted models. The maternal heritability estimates were in the range from 0.01 to 0.16, while the maternal common environmental variance ranged from 0.01 (EW1) to 0.21 (BW1) according to the fitted models. Our study demonstrated that model choice is an important factor in an accurate estimation of production and reproduction traits. A negative correlation was found between direct and maternal additive genetic effects (ram). The predicted genetic gains by the regression of breeding value on the generation number amounted to 9.99, 1.32, 0.06 and -1.44 for BW12, EN, MEW and ASM, respectively. Regarding the program of the Mazandaran native fowl breeding center in producing dual purpose chickens, despite the negative correlations between sonic of the selected traits (BW12, EN, ASM, and MEW), the genetic gain was observed in all selected traits of MNF during 23 generations. Taken together, it was concluded that including the direct genetic effect and maternal effects in the model will result in improving the selection efficiency for production and reproduction traits in fowl.