Estimation of genetic parameters for body weight traits and pelt quality score in Iranian Karakul sheep

- Genetic parameters for birth weight and weight at different ages until yearling as well as for pelt quality score were estimated in Iranian Karakul sheep.
- The values of heritability for the same traits and the phenotypic correlations were estimated.
- A good possibility of genetic improvements in Karakul sheep breed seems feasible as the studied traits were moderately heritable.

Genetic parameters for birth weight (BW), weight at 3, 6, 9 months of age (3MW, 6MW, 9MW), yearling weight (YW) and pelt quality score (PELT) were estimated in Iranian Karakul sheep. Data and pedigree information were obtained from the Breeding Station of Karakul sheep located in North Khorasan province in Iran from 1994 to 2009 on 5437 lambs descended from 193 sires and 1886 dams. Six different animal models were fitted, differentiated by including or excluding maternal effects, with and without covariance between maternal and direct genetic effects. The most suitable model amongst all six models was determined based on likelihood ratio tests for each trait. In addition, multivariate analysis was carried out among the considered traits to estimate the genetic and phenotypic correlations. Direct heritability estimates for BW, 3MW, 6MW, 9MW, YW and PELT were 0.21, 0.10, 0.14, 0.18, 0.21 and 0.004, respectively. All the phenotypic correlations estimates among body weight at different ages were positive. The estimates of phenotypic correlations for PELT-BW and PELT-3MW were low and positive while the remaining were low and negative. The estimates of direct genetic correlations between body weights were positive; whereas those among PELT and liveweights were negative. Current estimates of genetic parameters in Iranian Karakul breed may be used to design selection programme. Our results showed that improvement of growth performances seems feasible, as the studied traits were moderately heritable, although the heritabilities at 3MW and 6MW were quite low. However, selection for BW should be judicious in order to prevent unfavorable consequences on pelt quality. So, considering the high genetic correlations between 3MW and other body weight traits, the genetic improvement of 3MW should be one of the main selection goals.