Application of random regression model on genetic analysis egg production in native chiken of Fars province

The genetic changes of periodic records of egg production were investigated using Random Regression models. The used data were measured on 2310 birds descended from 46 sires and 618 dams. Of these 2257; 2205; 2102 and 1965 records of egg numbers were collected at 20-32 (1st period), 32-44 (2nd period), 44-56 (3rd period) and 56-68 (4th period) weekly, respectively. In the model analysis all important fixed (such as age and hatch) and random effects (such as direct additive genetic effects and animal permanent environmental effects) were included. Genetic analysis were started with k=2 for both direct additive genetic effects and animal permanent environmental effects; and completed with higher order of fitting up to k=4. Fitting a model with k=3 for the additive genetic effects and k=2 for animal permanent environmental effects was found as the most parsimonious model. Accordingly, the heritability of egg number for period 1, period 2, period 3 and period 4 were estimated to be 0.43, 0.12, 0.16 and 0.11, respectively. The proportion of permanent environmental variance to phenotypic variance was increased from 0.38 for 1st period to 0.6 for 4th period. In this study, the genetic correlations across the ages of egg production were estimated. The value of the genetic correlations shows that the ages of egg production represent 4 different traits. Therefore the selection accuracy could be increased when additional records. However, the benefit of using the additional measurements in the breeding program should be investigated.