Aim: To assess that metabolic status of spermatozoa could provide a useful tool for evaluation of semen quality.
Methods: The accuracy of the spectrophotometric application of the resazurin reduction assay was assessed using receiver operating characteristic (ROC) analysis.
Results: Areas under ROC curves (AUC) for motile sperm concentration and sperm index (SI) (sperm concentration multiplied by the square root of percentage sperm motility multiplied by the percentage normal sperm morphology) were 0.922. The best discrimination between poor and good semen samples according to the SI was achieved at a cut-off point of A610 = 0.209, where high sensitivity (94.1%) and specificity (91.7%) were calculated. The assay was less accurate when motile sperm concentration was used as the criterion value, yielding sensitivity of 88.2% and specificity of 87.5%, respectively. Likelihood ratios (LR) indicate that absorbances lower than 0.209 were at least 11.3 times as likely to be found in good semen samples than those in poor according to the SI, whereas in the case of motile sperm concentration, the LR was calculated to be 7.06.
Conclusion: These results show that the resazurin reduction assay combined with spectrophotometry is an accurate method of assessing the quality of boar semen.