Spectrophotometric Analysis of the Resazurin Reduction Test as a Tool for Assessing Canine Semen Quality

The resazurin reduction test (RRT) was subjected to spectrophotometric analysis to evaluate the quality of canine semen. Twenty four samples of canine semen were analysed. The absorption peaks for resazurin and resorufin were determined at 615 and 580 nm, respectively. The RRT ratio (RRT_sperm-the ratio for samples containing spermatozoa, RRT_plasma-the ratio for samples containing seminal plasma) was calculated by dividing the absorbance at 580 nm by the absorbance at 615 nm. Spearman’s correlation test was used to determine the significance of correlations between the analysed sperm parameters and the results of the resazurin reduction assay. The RRT ratio was highly correlated with sperm motility (r=0.68, P<0.01), progressive sperm motility (r=0.61, P<0.01), the subpopulation of cells with rapid velocity (r=0.72, P<0.01), and the subpopulation of cells with medium velocity (r= -0.54, P<0.05). A negative correlation was observed between the reducing capacity of seminal plasma vs. sperm with plasma membrane integrity (r= -0.60, P<0.01) and sperm with normal morphology (r= -0.58, P<0.01). The RRT test can be used as an additional tool for evaluation of the quality of canine semen.