Comparative effects of different zinc sources and inclusion levels on growth performance, antioxidant status, and meat quality in fattening lambs.

This study was conducted to evaluate the effects of different dietary zinc sources and inclusion levels on growth performance, organ development, antioxidant status, serum biochemical parameters, and meat quality traits in fattening lambs. Twenty-four male Baluchi lambs, 3 to 4 months old, with an average initial body weight of 20 ± 2 kg, were randomly allocated to four dietary treatments with six lambs per group. The experimental treatments included: (1) a basal diet without zinc supplementation (control), (2) the basal diet supplemented with 100 mg/kg dry matter zinc as zinc oxide, (3) the basal diet with 25 mg/kg dry matter zinc as nano zinc oxide, and (4) the basal diet containing 50 mg/kg dry matter zinc as zinc methionine. The feeding trial lasted 70 days, comprising 10 days of adaptation and 60 days of fattening. The results demonstrated that zinc supplementation, particularly in the form of zinc methionine, significantly improved final body weight, average daily gain, and carcass weight (p < 0.05). Antioxidant enzyme activities, including glutathione peroxidase and superoxide dismutase, were markedly elevated in the supplemented groups, while malondialdehyde concentrations in serum and meat were reduced, indicating enhanced oxidative stability. Serum zinc concentration and thyroid hormone levels (T3 and T4) were also significantly increased. Meat color attributes (lightness, redness, chroma) improved in the zinc-supplemented groups, whereas pH values remained unaffected. These findings indicate that zinc methionine was the most effective source for improving growth performance, antioxidant capacity, and meat quality, whereas nano zinc oxide mainly enhanced antioxidant status and oxidative stability without conferring growth performance benefits.