A study on inbreeding trend and its effect on body weight traits of Iran Black sheep in Abbas Abad breeding center of Mashhad

A data set consists of 6,030 weight records of Iran Black sheep (3,051 males and 2,979 females) progeny of 141 rams and 1525 ewes of Iran Black collected during 1973-2010 from Abbas Abad breeding centre, Mashhad were utilized for investigating inbreeding trend and its effect on body weight traits. The traits under consideration were birth weight (BW), weaning weight (WW), weight at 6-month (W6), weight at 9-month (W9), yearling weight (YW) and pre-weaning daily gain (PWDG). Inbreeding coefficient of all animals was computed using CFC software. A mixed linear model was applied for analyzing the data using SAS software. Among the animals, 5,333 (88.44%) were inbred indicating that the effective number of base population might be low. Average (standard deviation) of inbreeding coefficient were found to be 8.78 (6.34) and 9.33 (5.83) % for whole and inbred populations, respectively. Minimum and maximum inbreeding coefficients were 0 and 38.48 %, respectively. In whole population, average (standard deviation) of inbreeding coefficients were 8.75 (6.31) and 8.82 (6.37) % for male and female lambs, respectively. The corresponding figures were 8.69 (6.25) and 8.90 (6.37) % for single and twin lambs, respectively. Inbreeding depression was detected for WW, W3, W6, W9 and YW in twin males, for BW in twin females, and for W9 in twin females. Annual trends of inbreeding coefficient were 0.2022 and 0.1632 % for whole and inbred animals which were found to be statistically significant (P<0.0001).