Effect of reduced glutathione (GSH) supplementation to Tris-egg yolk extender on chilled semen variables of dogs.

One reason for reduced longevity of chilled dog semen is oxidative stress. The antioxidant glutathione (GSH) improves viability of frozen-thawed dog sperm, but its effect on chilled dog semen has not been investigated. An experiment consisting of two parts was performed: Sperm rich fractions, SRF, were split, diluted with a Tris-egg yolk (TEY) extender containing 0, 5 or 10 mM GSH and stored at 4 °C for 10 days (Part 1; n = 19) or 4 days (Part 2; n = 11), respectively. For Part 1 of the study, percentage (%) of motile, viable, morphologically abnormal spermatozoa and % acrosomal deviations were assessed on days 0, 1, 2, 4 and 10 after dilution. For % sperm motility, samples from all three aliquots of each SRF (0/5/10 mM GSH) were pipetted simultaneously and analysed in a randomised order (time point of analysis, TPA). In Part 2 of the study, motility analysis was performed during 4 days storage and samples were analysed immediately after pipetting (part 2). Most investigated parameters were affected by storage time. For motility variables, there was an effect of GSH identified for circular, CM (ANOVA, Part 1: P =  0.05, Part 2: P < 0.0001) and local motility, LM (ANOVA, Part 2: P =  0.004). Furthermore, there was a trend for an interaction between time and sperm treatment for CM (Part 2: P =  0.077). In conclusion, in the present study there was not an overall positive effect of GSH addition (5/10 mM) on sperm motility in chilled dog semen samples that were characterised to be of good quality during 4- and 10-days of storage.