Dietary supranutritional supplementation of selenium-enriched yeast improves feed efficiency and blood antioxidant status of growing lambs reared under warm environmental condition.

The objective of this study was to investigate the impacts of dietary supranutritional supplementation of selenium-yeast (SY) on growth performance, blood cells, antioxidant status, and metabolic profile of lambs. Twenty-one Kermani male lambs (28.5 ± 2.6 kg of body weight) were used in a completely randomized design for 8 weeks under warm condition with temperature-humidity index (THI) of 81.3 ± 0.37 unit. The lambs were randomly divided into 3 groups given the basal diet either un-supplemented (control group) or supplemented with 0.6 or 1.2 mg of Se/kg dry matter (DM) as SY. Average daily Se intake was 0.12, 0.83, and 1.54 mg in lambs on control, 0.6 mg and 1.2 mg of supplemental Se treatments, respectively (P < 0.0001). The results showed that average daily gain tended to be higher in lambs received Se-supplemented diets than those fed the unsupplemented diet (P < 0.1). Feed efficiency improved by SY supplementation, thereby feed to gain ratio (FG) reduced 19 and 17% respectively in lambs fed 0.6 (FG = 6.58) and 1.2 (FG = 6.7) mg of Se/kg DM compared to those of the control (FG = 8.12) (P < 0.05). Feeding 1.2 mg of Se to growing lambs not only improved blood total antioxidant capacity (T-AOC) as 18.1% and glutathione peroxidase activity (GSH-Px) as 17.6%, but also made 13.1% reduction in serum malondialdehyde (MDA) concentration as a lipid peroxidation marker (P < 0.05). Despite its statistical insignificance (P > 0.05), erythrocyte superoxide dismutase (SOD) activity was also greater in Se-fed groups compared to that of the control. Based on the obtained data, lambs fed 1.2 mg of Se/kg DM, had lower serum urea concentration and albumin to globulin ratio than those on unsupplemented diet (P < 0.05). Moreover, increased RBC count was observed in lambs received 0.6 mg of supplemental Se (P < 0.05). Selenium-enriched yeast supplementation gave rise to increased blood lymphocyte percentage (P < 0.05). The results also indicated that dietary high Se feeding had no adverse effects on blood metabolites including glucose, total protein, albumin, globulin, liver enzymes, and triglyceride content. In the overall, these findings suggest that Se-enriched yeast is a kind of safe Se source for sheep and its dietary supranutritional supplementation for 8 weeks improves feed efficiency of growing lambs. Furthermore, increasing the supplemental Se to 1.2 mg/kg of diet promotes lambs' blood antioxidant status without inducing any detrimental impacts on cell metabolism.