Estimation of inbreeding coefficient and its effects on growth traits in Zandi sheep

The aims of this study were estimation of inbreeding coefficients and its effects on birth weight (BW), weaning weight (WW), 6 month weight (6MW), 9 month weight (9MW) and yearling weight (YW) of Zandi sheep. The pedigree data and records were of 6140 Zandi sheep, which were collected during 1991-2011 by Zandi sheep Breeding Center located in Tehran. 36.32 % of the animals were inbred. Mean inbreeding coefficient for the herd and inbred population was 1.22 and 3.61 percent, respectively. Inbreeding coefficient was increased by 0.02±0.01 percent per year (P<0.05). Effects of inbreeding on traits were estimated by restricted maximum likelihood method using 12 animal models. The most appropriate model for each trait was determined based on Akaike’s Information Criterion. The regression coefficients of inbreeding on BW, WW, 6MW, 9MW and YW were -3.49±4.87 (P>0.05), -42.20±20.18 (P<0.05), -60.35±25.12 (P<0.05), -40.70±24.80 (P>0.05) and -76.55±29.24 gr (P<0.01), respectively.