Capacitation and acrosomal exocytosis are enhanced by incubation of stallion spermatozoa in a commercial semen extender.

The research investigates the impact of different mediums on the health and functionality of stallion sperm cells. The findings suggest that a medium called skim milk extender enhances natural sperm processes, but may shorten their lifespan.

Introduction

• The study seeks to explore the reasons for the decreased motility and fertility often observed in preserved stallion semen.
• One potential cause is suspected to be the medium in which the sperm is extended, with the hypothesis being that this could induce premature capacitation during storage.
• The research proposes that premature capacitation and acrosome reaction can limit fertility by reducing the sperm’s capacity to penetrate the egg.

Hypothesis and Experiment Design

• The researchers speculate that skim milk-based semen extenders, used during cooled storage may stabilize sperm membranes, thus slowing down their motility and extending their longevity. But, their efficiency in vivo may consequently be hampered.
• To investigate these effects, the research involved evaluating sperm function after incubation in skim milk extender and Tyrode’s medium (containing albumin, lactate, and pyruvate) at 37 degrees Celsius.

Methods and Findings

• Sperm motility was analyzed, intracellular calcium levels were measured, and the ability of sperm to undergo acrosome reaction was compared between the two mediums.
• The results suggested that skim milk extender facilitated capacitation, demonstrated by an increase in both intracellular calcium and acrosome reactions, and a decrease in motility, as compared to Tyrode’s medium.

Conclusion

• The findings supported the theory of a shortened functional lifespan for horse sperm in the skim milk extender medium.
• This might entail a need for refinement in cooled semen preservation techniques for improving the fertility of transported equine semen.