The effect of high levels of dietary zinc on growth performance, carcass characteristics, blood parameters, immune response and tissue minerals in growing Boer-cross goat kids

Abstract

An experiment was conducted to determine animal performance, carcass traits, blood metabolites, immune responses, and tissue minerals in goats fed high levels of zinc (Zn). Twenty-one Boer-cross (Capra aegagrus hircus) growing goat kids (BW, 22.9 ± 1.4 kg, 4–5 months old) were housed individually and fed twice a day 80:20 grain mix: bermudagrass hay (BGH) diet ad libitum for 86 days. Goats in control group (0Zn) received orally 5 mL of water (1.95 + 0.03 ppm Zinc) with no added Zn. Treatment groups, 100Zn and 200Zn received 5 mL water containing additional 100 or 200 mg Zn as Zn sulfate heptahydrate, respectively. Average daily gain (ADG), DM intake, feed conversion ratio (gain: feed), carcass traits, majority of blood attributes and metabolites, and humoral immunity were similar among the treatment groups. However, cell-mediated immune response was higher for 100Zn group (quadratic; P = 0.04). Goats receiving high levels of Zn increased serum calcium (linear; P = 0.03), glucose (linear, P = 0.02), and lymphocytes (linear, P = 0.05 and quadratic; P = 0.01). Manganese (Mn) level in the liver increased (linear, P = 0.01), while liver copper (Cu) decreased (linear, P = 0.04) as the level of Zn was increased in the diet. Zinc in the feces increased (linear, P = 0.001), with no changes in urine Zn. Blood mineral phosphorus was reduced (linear, P = 0.03), and magnesium, and potassium tended to decrease (linear, P = 0.06 and 0.07, respectively) with increasing Zn levels in diet. High levels of Zn supplementation did not affect animal performance and carcass characteristics; however, improved immunity and impacted liver Mn and Cu.