Effects of dietary copper on nutrient digestibility, growth performance and plasma copper status in cashmere goats

Thirty-six 1.0-year-old wether Inner Mongolian White Cashmere Goats (IMWG) (BW = 28.8 ± 1.35 kg) were used to determine the effects of dietary copper (Cu) concentration on growth performance, nutrient digestibility and plasma Cu status during the cashmere non-growing period. Wethers were stratified by weight and randomly assigned to four dietary treatments that contained 0 (control), 10, 20 and 30 mg of supplemental Cu/kg DM. The Cu concentration was 7.38 mg/kg DM in the basal diet. Body weight was recorded on two consecutive days at the start and end of the 60-day experimental period. Blood samples were collected via the jugular vein on day 0, 15, 30, 45 and 60. Average daily gain and gain efficiency were higher (P < 0.01) in the treatment group supplemented with 10 mg Cu/kg DM compared with other groups, and were lower (P < 0.01) in the treatment group supplemented with 30 mg Cu/kg DM compared with other groups. The supplement providing 30 mg Cu/kg DM decreased average daily feed intake (P < 0.01). Copper supplementation had no influence on digestibility of DM and CP (P > 0.05), however, NDF and ADF digestibility and N retention of the treatment group supplemented with 10 mg Cu/kg DM were higher than that of the treatment group supplemented with 30 mg Cu/kg DM (P < 0.01). Plasma Cu concentrations were increased (P < 0.05) by all Cu supplemented treatments on day 15, 30, 45 and 60 of the experiment (P < 0.01), but did not differ between groups supplemented with Cu (P > 0.05). In conclusion, supplementation of the basal diet with 10 mg Cu/kg DM (the total dietary Cu level of 17.4 mg/kg DM) in the basal diet enhanced growth performance and improved nutrient digestibility and plasma Cu status of cashmere goats.