Refrigerated storage of ram sperm in presence of Trolox and GSH antioxidants: effect of temperature, extender and storage time.

Antioxidants have a potential to improve the quality and fertility of refrigerated-stored ram semen. Reduced glutathione (GSH) and Trolox (0.2, 1 and 5mM) were evaluated in ram semen preserved at 15 and 5°C up to 48 and 96h, respectively. Extenders were also evaluated (15°C: Tris-citrate-fructose, TCF, without lipids, and TES-Tris-fructose 10% egg yolk, TTF-EY; 5°C: TTF-EY and 3.5% soybean lecithin, TTF-SL; INRA96 at both temperatures). Storage at 5°C resulted in poorer quality than 15°C up to 48h, while allowing acceptable quality at 96h. Antioxidants had few effects on sperm quality, with use of Trolox resulting in reduced motility and viability in TCF. Storage at 15°C in the TCF extender resulted in decreased motility, viability and mitochondrial activity compared with use of TTF-EY. Sperm quality when storage was at 5°C was similar, but storage in TTF-SL resulted in decreased motility and mitochondrial activity. Acrosomal status was only slightly affected by extender and antioxidant. Mitochondrial activity was improved by antioxidants in TTF-SL, and GSH at 5mM when semen was stored at 5°C in TTF-EY. A preliminary artificial insemination trial indicated that supplementation with GSH has the potential for improving lambing (P<0.1). In conclusion, use of antioxidants resulted in lesser effects than extender composition or storage time on quality of ram semen. Use of Trolox negatively impacted sperm quality and GSH had some positive impacts. The use of soybean lecithin requires further research to assess its impact on mitochondria.