Quality and reactive oxygen species of extended canine semen after vitamin C supplementation

The objective of this study was to evaluate the quality of extended dog semen processed with diluents containing various concentrations of vitamin C. Ejaculates from five dogs were collected, pooled and evaluated for concentration, sperm motility, rapid steady forward movement (RSF-movement), viability, acrosomal integrity and by the hypo-osmotic swelling test. Also, superoxide (O2−) production, hydroxyl radicals (OH) and total reactive oxygen species (tROS) were determined. The pool was divided in five aliquots, which were diluted to a final concentration of 66 × 106 spermatozoa/ml with a Tris–glucose–egg yolk extender containing one of the following concentrations of vitamin C (0, 0.1, 0.5, 1 or 2.5 mM). The semen aliquots were chilled and preserved at 4 °C. Portions of chilled semen were removed at 24 and 72 h, and semen quality was evaluated after rewarming. This process was repeated 10 times in pooled semen of the same origin and data were analysed by one-way analysis of variance. At both times, none of the semen quality parameters were positively influenced (p > 0.05) by vitamin C supplementation. At 24 h, none of the reactive oxygen species (O2−, OH, tROS) were significantly altered. At 72 h, significant reductions of O2− production were observed by the concentrations of 0.1, 0.5 and 2.5 mM compared with the 0 mM concentration (p = 0.049). Also, at 72 h, the 2.5 mM concentration showed significantly lower OH values in comparison with the control group (p = 0.048). In conclusion, addition of vitamin C to semen extenders does not benefit the quality of canine extended spermatozoa.