Abstract: Oregano oil can significantly improve growth and immunity in domestic animals.The purpose of this research was to study the effects on growth performance, slaughtering performance and carcass quality of Hexi cashmere goat by adding oregano oil to their diets. The control group was fed a basic diet, while in the trial groups, 4 and 7 g additives with oregano essential oil 52 and 91 mg respectively were added to the basal diet, respectively. Animals both in control and treatments groups were the same age and weight. Each treatment had 3 replicates each consisting 5 goats.The feeding period was 90 days with monitoring undertaken every 30 days. The results showed that the average daily gain of Hexi cashmere goats in control group, 4 g group and 7 g group was 96.30, 172.22 and 169.82 g·d^-1, respectively, with the control group being significantly less than those groups supplemented with oregano oil (P<0.05). The carcass weights were 20.24, 24.18 and 23.90 kg in control, 4 and 7 g groups respectively. The slaughter rate, carcass net meat weight and the marbling of the longissimus dorsi muscle of 4 g group and 7 g group were significantly higher than them of control (P<0.05), but there was no difference between the oregano treatments groups (P>0.05). There were no differences in meat pH, cooked meat rate, water loss rate, tenderness and loose on cooking between treatments (P>0.05). Adding oregano oil to the diet improved the growth of Hexi cashmere goats; the optimum level was 52 mg·goat^-1·d^-1.

Key words: oregano oil, Hexi cashmere goat, production performance, carcass traits, mutton quality