Effect of Fat-Tail Docking on the Reproductive Performance in Ghezel and Mehraban Sheep

78 Ghezel and 76 Mehraban sheep were used to evaluate the effect of fat-tail docking on reproductive performance. Within two days after birth the tails of 32 Ghezel female lambs and 28 Mehraban female lambs were docked using a tight rubber ring. The lambs were allowed to reproduce for three lambing opportunities and their reproductive performances were evaluated. The effect of docking on the fertility (ewe lambing per ewe exposed), litter size (lambs born per ewe lambing) were evaluated employing a multivariate logistic regression procedure, through the inclusion of tail docking in a 2-way interaction with breed, the fixed effect of parity and the random effect of the ewe. The results showed that the interaction of docking and breed significantly impacted fertility rate (P 0.05). In Ghezel ewes, docking reduced fertility [odds ratio (OR) (95% confidence interval (CI))= 0.29 (0.11-0.79) for docked vs. undocked Ghezel ewes]. Docking had no effect on fertility in Mehraban ewes [odds ratio (OR) (95% confidence interval (CI))= 1.19 (0.38-3.71) for docked vs. undocked Mehraban ewes]. The interaction effect of docking and breed had no impact on litter size, lamb birth weight and lamb weaning weight.