Estimation of genetic parameters and inbreeding depression on biometric traits of Iranian Moghani sheep

Background and Aim: The objectives of this study were to estimate the genetic parameters and effect of inbreeding on biometric traits of Iranian Moghani sheep.Methods: The data used in this study consisted of biometric traits collected at the Breeding station of Moghani sheep, Ardebil province, Iran. The traits under consideration were height at withers, height at rump, body length, heart girt and leg circumference. The influence of environmental effects on traits, such as sex, type of birth and dam age at lambing, year and season were determined using analysis of variance. The pedigree information collected between ۱۹۹۰ and ۲۰۱۵ was used to calculate inbreeding coefficients. For estimating the inbreeding depression, only animals with pedigree completeness index of greater than ۰.۶ were considered as reference population and inbreeding coefficients of animals were included in the model as covariate. Six different animal models were fitted, differentiated by including or excluding maternal effects, with and without covariance between maternal and direct genetic effects. Final model for each trait was selected according to the comparison of the Akaike Information Criterion. A lower AIC value indicated a better fit. The variance components and genetic parameters were estimated using restricted maximum likelihood methods by WOMBAT software.Results: The effect of year-season, sex, type of birth and dam age at lambing was significant for all traits. Estimates of heritability for height at withers, height at rump, body length, heart girt and leg circumference were ۰.۰۴, ۰.۰۵, ۰.۰۰۶, ۰.۰۱۱,۰.۰۱۶, respectively. Inbreeding had a negative effect on the biometric traits in the present study except for height at withers. The regression coefficients of height at withers, height at rump, body length, heart girt and leg circumference on inbreeding were estimated to be -۰.۰۰۱, -۰.۰۱, ۰.۰۲, -۰.۰۲ and -۰.۰۱.Conclusion: According to the results, the heritability estimate of biometric traits in Moghani sheep was low, which would slow down the implementation of selection and genetic progress in these traits. Also, according to the results, inbreeding had a significant negative effect on biometric traits in this breed. Therefore, a controlled mating system to avoid an increase of inbreeding should be applied to this herd.

کلیدواژه ها:

Heitability ، Biometric Traits ، Inbreeding Depression ، Moghani Sheep