Effect of high levels of Cu supplement on growth performance, rumen fermentation, and immune responses in goat kids

An experiment was conducted to determine the effect of high levels of supplemental Cu (as Cu sulfate) on growth performance, rumen fermentation, and immune responses in goats. Fifteen Boer × Spanish goat kids (BW = 21.3 ± 0.7 kg) were fed basal diet containing 14 ppm Cu and were randomly assigned to three treatments: (1) control (no supplemental Cu); (2) 100 mg supplemental Cu/day; (3) 200 mg supplemental Cu/day. Copper sulfate was placed in gelatin capsules and inserted in to the esophagus via a balling gun before the morning feeding. Animals consumed ad libitum twice a day a 70:30 grain:hay diet. Body weight was recorded after 4 h withdrawals from water, for two consecutive days every 2 weeks for 14 weeks. Rumen samples were collected at days 44, 74, and 94 of experiment and blood samples were collected via jugular vein. The cell-mediated immune response was determined via lymphocyte proliferation assay using concanavalin A (ConA) and phytohemagglutinin A (PHA). Humoral immunity was determined on days 50 and 64. Goats were injected with chicken ovalbumin (2 mg/goat) in Freund's incomplete adjuvant. Serum samples were subjected to an ELISA test on days 57, 72, and 98 in order to measure the antibody titer to the chicken ovalbumin. Average daily gain was improved (quadratic, P = 0.05) with 100 mg Cu intake. Protozoa count tended to decrease (linear, P = 0.08) with higher Cu supplementation; however, acetate, propionate or butyrate (mol/100 mol) did not differ (P > 0.10). An increase (linear, P = 0.03) in leukocyte count was observed, with higher neutrophils (quadratic, P = 0.04) and lower lymphocytes (quadratic, P = 0.01) associated with 100 mg Cu supplementation. ConA-induced lymphocyte proliferation was higher (P = 0.05) in 100 mg Cu group on day 98; however, PHA-induced lymphocyte proliferation was higher on day 72 (linear, P = 0.01) in the Cu-supplemented groups. Antibody titer to the chicken ovalbumin tended to be higher (linear, P = 0.08) on day 72 and it was higher (linear, P = 0.02) on day 98 in the Cu-supplemented groups. These results indicated that Cu-supplemented at 100 mg/day, improved gain and enhanced the immune response in goat kids.