GENETIC PARAMETERS FOR GROWTH PERFORMANCE TRAITS OF EGYPTIAN BARKI LAMBS USING RANDOM REGRESSION MODEL

Variance components and genetic parameters for growth traits were estimated for Barki lambs using the average information REMLF90 (AIREMLF90). A total of 3205 Barki lambs’ records over the period from 1984 to 2017 from experimental Borg Al-Arab station belonging to Animal Production Research Institute (APRI) were analyzed by fitting Random Regression Model (RRM) with Legendre polynomials (LPs) for body weight traits from birth up to 480 days. Gender, type of birth, year, season and age of dam were considered as fixed effects in addition to the fixed regression on Legendre polynomials, while random regression of additive genetic and permanent environmental effects were considered as random factors in the model. The results showed that all fixed factors and some interactions were significant for all studied traits (P<0.05). Quadratic equation was the best description for growth curve. Additive genetic and permanent environment variances ranged from 0.88 to 6.08 and from 0.88 to 15.33 for birth and thirteen months weights, respectively. Additive genetic and permanent environment covariances ranged from 0.05 to 16.06 and from 0.08 to 9.20 for birth with six months weights and for weaning with ten months weights, respectively. Direct and total heritabilities ranged from 0.05 to 0.41 and from 0.08 to 0.74 for four months and birth weights, respectively. Additive, genetic and phenotypic correlation coefficients were the lowest between birth weight with other studied traits and  the highest between ten months weight with other studied traits. Phenotypic variances were oscillated between 2.27 for birth weight to 22.56 for seven months weight, while, residual variances were oscillated between 0.06 for birth weight to 14.05 for four months weight. Therefore, ten months of age recommended to be the best criterion for selecting Egyptian Barki lambs for meat production.