عنوان مقاله [English]
Introduction Iranian native fowl, which are kept in different parts of Iran, are characterized by a long history and vast diversity. Iranian indigenous chickens are meat-cum-egg type. There is evidence of variation in Iranian native fowl for different traits. In many developing countries, the local gene pool still provides the basis for the poultry sector. The genetic resource base of indigenous chickens can form a basis for genetic improvement and diversification to produce a breed adapted to local conditions. However there is little information about existing or potential productivity and production characteristics of indigenous chickens. Breeding of native fowl is important for small farmers to produce more income and also to conserve genetic variation of native breeds. Extensive investigations on the genetic characteristics of economic traits should be conducted before designing a breeding program. The correct method of evaluation of genetic parameters to select the best animals is very critical. Gibbs sampling Bayesian method was used to estimate genetic parameters. This method includes the definition of prior and posterior distribution and then combines to form full conditional posterior distributions for the analysis of complex models with a large number of records. This method is expected to better results achieved. The objective of the present study was to study the genetic characteristics of growth and egg production traits consisting heritability and genetic and phenotypic correlations in native fowl of Khorasan Razavi province.
Materials and Methods The collected information of about 21000 native fowl of Khorasan Razavi Province during 2009 to 2012 were used. Genetic parameters of studied traits were estimated via Bayesian implementation of Gibbs sampling using GIBBS3F90 software. Heritability and genetic and phenotypic correlations between traits were estimated using univariate and bivariate animal models. First, to increase the accuracy of calculations, according to the characteristics of the normal distribution, records with more or less than three standard deviations from the mean of each character were considered as outliers and were omitted from the data. Analysis of variance was performed for each studied trait to find out the significant fixed effects. To obtain the marginal posterior distributions for each parameter, Gibbs sampling technique in a special case of MCMC algorithm was used.
Results and Discussion Average values of body weight at 8 (BW8) and 12 weeks (BW12) of age, weight and age at sexual maturity (WSM, ASM), egg number (EN) and egg weight (EW) were684.16 g, 1243.75 g, 1811.41 g, 164.21 days, 50.36 g, 38.86 number, respectively. Heritability of BW8, BW12, WSM, ASM, EN and EW were 0.37, 0.40, 0.30, 0.31, 0.46 and 0.11, respectively. The highest heritability among performance traits belonged to egg weight between 28 to 32 weeks of production period (0.46) and the lowest heritability was observed for egg number during first 12 weeks of production (0.11). Moderate to high heritability values show the importance of genes effect on the phenotypic variance and the effectiveness of selection for genetic improvement in the studied traits. Genetic correlation between BW8 and BW12 was high (0.86) and they showed high genetic correlations with ASM (0.84 and 0.69, respectively). These results demonstrated the similarity of genetic structure of these traits. Genetic correlations of BW8, BW12 and WSM with ASM were positive. Therefore, selection for increased growth rate at different ages will unfavorably increase ASM. Growth and egg production traits are both important in native fowl because they are dual-purpose breeds.
Conclusion The average body weight at different ages in native fowl of Khorasan Razavi Breeding Center were higher than other native fowl breeding centers which shows their proper capacity for meat production. Native fowl of Khorasan Razavi showed relatively suitable performance in egg weight and the age of sexual maturity but the produced egg number needs more attention and must be improved in this breeding center. Because of unfavorable genetic correlations between growth traits and ASM, selection for increased growth and decreased ASM using a selection index would be necessary to improve the economic performance of native fowlin Khorasan Razavi province.