Comparison of Effects of Different Antioxidants Supplemented to Long-term Extender on Boar Semen Quality Following Storage at 17ºC

The use of antioxidants as semen additives in the extender has been proposed to improve sperm function during cool storage. The objective of this study was to compare the effects of different antioxidant supplementation in extender on boar semen quality during storage for 10 days at 17ºC. Semen samples (n=18) were divided into 10 aliquots and diluted with Reading extender supplemented with three different concentrations of water-soluble glutathione, L-carnitine, and vitamin E analogue Trolox (0.1, 1 and 5mM). All samples were stored in a refrigerator at 17ºC for 10 days. Sperm motility was assessed at Days 1, 4, 7 and 10 of storage under a phase-contrast microscopy. Percentage of live sperm with normal apical ridge and high mitochondrial energy status was assessed at Days 1, 5 and 10 of storage by fluorescent multiple staining using propidium iodide (PI), fluorescein isothiocyanate-labeled peanut (Arachis hypogaea) agglutinin (FITC-PNA) and 5,5’,6,6’-tetrachloro-1,1’,3,3’ tetraethylbenzimidazolyl-carbocyanine iodide (JC-1), respectively, under fluorescent microscopy. The sperm motility was greater in 1 mM of glutathione supplementation than the others (p<0.01). However, the percentage of live sperm with normal apical ridge and high mitochondrial energy status did not differ among the groups (p>0.05). The supplementation of semen extender with 1 and 5 mM of vitamin E had detrimental effect on the quality of stored semen (p<0.01). In conclusion, the addition of 1 mM dose of glutathione can be recommended as an alternative component of boar semen extender for long-term cool storage.