Effect of Caffeine and Pentoxifylline Added Before or After Cooling on Sperm Characteristics of Stallion Sperm.
Authors: Rossi Melissa, Gonzalez-Castro Raul, Falomo Maria Elena
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Caffeine and Pentoxifylline in Cooled Stallion Sperm Maintaining sperm quality during chilled storage remains a significant challenge in equine reproduction, with various additives proposed to counteract the motility decline that reduces fertility potential. Rossi and colleagues tested whether caffeine (5 mM) and pentoxifylline (3.5 mM)—agents known to enhance sperm metabolism in other species—could preserve or restore function in cooled stallion semen, examining whether timing of addition (before versus after 24-hour cooling at 4°C) affected outcomes. Whilst both additives significantly improved motility parameters during the initial rewarming period (particularly pentoxifylline when added post-cooling), this short-term benefit came at a substantial cost: prolonged exposure to either additive significantly increased tail defects, reduced the proportion of morphologically normal sperm, and impaired both viability and membrane integrity as assessed by hypo-osmotic swelling testing. The timing of additive introduction made little practical difference to outcomes. For practitioners using cooled semen, these findings suggest that whilst caffeine and pentoxifylline may provide a brief motility boost during initial handling and assessment, their use may compromise longer-term sperm quality and fertility potential—making their routine addition to cooled extenders counterproductive for shipment or storage beyond a few hours.
Read the full abstract on PubMed
Practical Takeaways
- •While caffeine and pentoxifylline may provide temporary motility improvements in cooled stallion semen, the increased tail defects and reduced sperm viability after extended storage make them problematic for practical breeding programs
- •If pentoxifylline is used, timing of addition (before or after cooling) does not matter, but benefits are limited to approximately 30 minutes of incubation
- •Current extender protocols without these additives may be preferable to avoid compromising overall sperm quality and long-term fertility potential in cooled semen collection
Key Findings
- •Caffeine and pentoxifylline significantly affected motility and kinematic parameters when added to cooled stallion sperm, with no difference between pre- or post-cooling addition
- •Pentoxifylline added after cooling improved motility for only 30 minutes but caused significant reduction during prolonged incubation
- •Both additives significantly increased tail defects (P < .003) and reduced morphologically normal sperm (P < .0001), impairing fertility potential
- •Prolonged exposure to caffeine or pentoxifylline compromised viability and membrane functionality despite short-term motility improvements