Bacteria-derived selenium enhances selenium deposition, antioxidant status, and epididymal sperm quality in growing lambs.

Selenium (Se) is an essential micronutrient involved in male reproductive physiology through its integration into selenoproteins that orchestrate antioxidant defense and spermatogenesis. This study compared the effects of inorganic and yeast- and bacteria-derived Se on the bioavailability, testicular development, sperm functional traits, epididymal plasma biochemistry, and testicular glycogen reserves in growing lambs. Twenty-four lambs (6-7 months old) were randomly assigned to four dietary groups (n = 6) for 90 days: control and sodium selenite (0.5 mg/kg), Se-yeast (0.5 mg/kg), and bacteria-derived Se (0.5 mg/kg) supplemented groups. Se supplementation significantly increased Se concentrations in serum, epididymal plasma, and testicular tissue (P < 0.0001), with bacteria-derived Se exhibiting the highest tissue deposition. Improved bioavailability enhanced testicular development, as evidenced by paired testicular weight, gonadosomatic index, and other morphometric parameters (P < 0.0001). Se also fortified the antioxidant architecture, upregulating glutathione peroxidase, superoxide dismutase, and catalase activities, while markedly reducing malondialdehyde levels (P ≤ 0.0004). Epididymal sperm quality improved significantly, including motility, concentration, membrane integrity, viability, and reduced abnormalities (P < 0.0001), without affecting the recovered fluid volume (P = 0.6306). Additionally, Se enhanced epididymal plasma biochemical profiles and increased testicular glycogen reserves (P < 0.0001). Overall, bacteria-derived Se resulted in superior tissue Se deposition and improved reproductive parameters compared to that from other sources. While these responses are likely associated with an enhanced antioxidant status, the specific Se species and underlying molecular mechanisms require further investigation. Consequently, bacteria-derived Se represents a promising alternative source for supporting male reproductive development in small ruminants.