Inbreeding Effects on Reproductive Traits of Mehraban Sheep

Inbreeding effects on reproductive traits were measured in Mehraban sheep using 10275 lambing records (1994-2011) from the Breeding Station of Mehraban sheep (Hamedan Province, Iran). The reproductive traits were litter size at birth per ewe lambing (LSB), litter size at weaning per ewe lambing (LSW), total litter weight at birth per ewe lambing (TLWB), total litter weight at weaning per ewe lambing (TLWW), litter mean weight per lamb born (LMWLB) and litter mean weight of lambs at weaning (LMWLW). Inbreeding depression was estimated by the Reg procedure of SAS. Inbreeding of all animals was calculated by INBUPGF90 program. All animals were grouped into two classes according to their inbreeding coefficients: the first class included non-inbred animals (F=0); and the second class included inbred animals (F>0). In different inbreeding classes, the LSW and LMWLB showed significant differences (P<0.05), but there were no significant differences in LSB, LMWLW, TLWB and TLWW traits. The regression coefficients of LSB, LSW, LMWLB, LMWLW and TLWW on lamb inbreeding were estimated to be 0.13±0.01, 0.36±0.02, -7.79±0.54, 38.01±4.80 and 108.89±14.18 (P