Carvacrol and Thymol Enhance the Quality of Beni Arouss Buck Semen Stored at 4 °C Thanks to Their Antimicrobial Properties

This study aims to investigate the impact of carvacrol and thymol on the quality of Beni Arouss buck semen stored in skim milk at 4 °C. Ejaculates were collected from eight Beni Arouss bucks weekly for 11 weeks, pooled, and then divided into three equal parts. Samples were diluted to 400 × 10⁶ sperm/mL in skim milk (control) and skim milk supplemented with a single dose of 200 µM carvacrol and thymol each. Evaluations of sperm motility, viability, abnormalities, membrane integrity, lipid peroxidation, and bacterial growth were conducted at 0, 6, 24, and 48 h of liquid storage at 4 °C. After 48 h of storage, the results indicate that the addition of carvacrol positively influences total and progressive motility and viability. However, it also leads to a decrease in lipid peroxidation and bacterial growth compared to the control group (<i>p</i> < 0.05). Thymol showed similar results to carvacrol, except for progressive motility (<i>p</i> > 0.05). Bacterial growth was negatively correlated with total and progressive motility and viability (<i>p</i> < 0.05), while no correlation between lipid peroxidation and these parameters was observed (<i>p</i> > 0.05). In conclusion, the addition of carvacrol and thymol to skim milk extender moderately improves the quality of Beni Arouss buck semen after 48 h storage at 4 °C due to its antimicrobial activity.