Estimation of genetic and phenotypic parameters and genetic trends of the growth traits in Zandi sheep

To estimate variance components and genetic parameters of growth traits in Zandi sheep, 5542 records during years 2005 to 2011 of herds under research center in Qom were used. Estimates of variance components with derivative-free restricted maximum likelihood method (DFREML) and using the animal model was estimated through six models using WOMBAT software. Year of birth, season of birth, lamb sex and birth (singleton and twin) and the herd showed significant effects (P<0.05) in the studied traits. Therefore, it was implemented as a fixed effects model. The magnitude of likelihood logarithm was estimated for the six models for all the traits. To ensure, the constant (AIC) was also used and the best model for each trait was reported. Direct heritability of traits was estimated based on the values of 3, 3, 2, 2, 2, 2, respectively, for total average birth weight, birth weight, total weaning weight, weaning weight, weights of 12 and 24 months of lambs of ewe were found to be 0.18, 0.17, 0.29, 0.23, 0.18 and 0.1, respectively. Average value of phenotypic and genetic direct and maternal traits in each year were estimated using the best linear unbiased prediction (BLUP) estimates, and the genetic trends of the traits were looked at for over 6 years. The average direct genetic birth weight and total birth weight of lambs of ewes and average of total weight and weaning weights of 12 and 24 months using a single-single analysis were 1.33 ± 0.07, 2.28 ± 0.4, 6.68 ± 2.1, 8.57 ± 1.9, 98.54 ± 22.1 and 205.11 ± 25.8 g, respectively.