Estimation of inbreeding depression on growth correlated traits in Karakul lambs

In this study, inbreeding coefficients and effect of inbreeding depression on growth traits were estimated using pedigree and body weight records of Karakul sheep kept (over a period of 24 years (1984-2008)) at the breeding station in Sarakhs, Razavi Khorasan, Iran. Inbreeding coefficients for all animals were estimated using Van Raden algorithm due to low pedigree completeness index. Inbreeding depressions on growth traits were estimated as the regression of body weight in different age, average daily gains in pre-weaning and post-weaning on animal and dam’s estimated inbreeding coefficients as co-variables. The mean of inbreeding for all animals, females and males were 1.59, 1.64 and 1.54 percent, respectively. Inbreeding depression per 1 percent increasing of individual inbreeding for birth, 3,6,9 and 12 month weight and average daily gains in pre-weaning and post-weaning was -0.005, -0.039, -0.117, -0.168, -0.17,-0.0004 and -0.0005 Kg, respectively. Inbreeding depression per 1 percent increasing of dam inbreeding for these traits was 0, -0.050, -0.014,-0.042, -0.055, -0.0006 and 0 kg, respectively. Estimated inbreeding coefficients for this breed showed high degree of close mating in this herd and due to the significant effect of inbreeding on some growth traits it is suggested that this breeding station should use a breeding plan to avoid mating of close relative animals and will use from assortative and compensatory mating.