Limits of grape byproduct inclusion in diets for lambs: Zinc supplementation to prevent copper poisoning

Abstract

The aims of the current study were to assess the inclusion levels of grape byproduct replacing jiggs hay in lambs diets and to evaluate signs of copper poisoning. Thirty-four Texel and Corriedale crossbred female lambs were used in a randomized block experimental design. The treatments comprised four levels of grape byproduct (0; 100; 200 and 300 g/kg DM) in replacement of jiggs hay. The diets were adjusted to the same ZnCu ratio (6:1) of the basal diet. Grape byproduct consumption at up to 30%, led to similar weight gain in the different treatments (P = .92), which was suitable for growing lambs. Grape byproduct in the diet had linear effect on GGT (P < .001) and AST (P < .0001) enzymes as well as on total bilirubin (P = .05). In addition, the highest grape byproduct addition showed the highest consumption of hay (P < .01). Hay replacement by grape byproduct at up to 300 g/kg in the DM was satisfactory to weight gain and did not negatively affect feed intake and weight gain of growing lambs. Maintaining zinc:copper ratio in sheep diets is not effective in preventing liver damage caused by increased dietary copper concentrations over a period of 70 days.