Evaluation of the effect of conventional and natural antifungals on motility and kinetics of cooled stallion semen.

Microbial growth in semen may cause a decline of sperm quality and fertility; however, the addition of antifungals to semen extender has been shown to impair the overall fertility of the sperm. The aim of this study was to evaluate the antifungal activity of conventional and natural compounds, and their effect on the motility and kinetics of cooled stallion semen. A total of 15 ejaculates from five stallions were collected using the artificial vagina. Each ejaculate was supplemented with: fluconazole at 12.5 (F1), 25 (F2) and 50 (F3) mg/ml; amphotericin-B at 6.5 (A1), 12.5 (A2) and 25 (A3) mg/ml (A3); clotrimazole at 12.5 (C1), 25 (C2) and 50 (C3) mg/ml; isoespintanol at 50 (I1), 100 (I2) and 150 (I3) µM; thymol at 50 (T1), 100 (T2) and 150 (T3) µM; and a control without supplementation. Motility and kinetics of semen at 0, 24 and 48 hr of cooling at 15°C were assessed using computer-assisted sperm analysis (CASA). At hour 48 of cooling, the antifungal effect of the treatments was evaluated. At hour 0 of cooling, amphotericin-B and I3 showed a reduction in most of the motility and kinetic parameters evaluated (p < .05). These treatments, and also C2 and C3, showed similar results at 24 and 48 hr of cooling. Thymol maintained motility and kinetics of the spermatozoa at all evaluated refrigeration times. Besides, I2 showed a decrease (p < .05) in the colony-forming unit compared to that in the control. It is concluded that thymol and isospintanol could be added as natural antifungals in extenders for stallion semen refrigeration.