Equine spermatozoal motility and fertility associated with the incorporation of d-(+)-mannose into semen extender.

This research investigates the impact of incorporating Mannose, a type of sugar, into semen extenders for horses, on sperm motility and fertility. The study shows that while high concentrations of Mannose can affect sperm motility, an extender containing up to 37 mg/mL Mannose can maintain motile spermatozoa for on-farm use and has the same fertilizing capability as traditional extenders.

Purpose of the Research

• The study aims to evaluate how mannose, a type of sugar known to decrease bacterial attachment to the uterine mucosa in mares, affects sperm motility and the subsequent ability of the sperm to fertilize when incorporated into semen extenders.
• The researchers sought a practical method of delivering mannose to the mare’s uterus during breeding, as bacteria can gain entry during the process.

Methodology and Experimentation

• In the first experiment, sperm motility was investigated in various semen extenders containing different concentrations of mannose – 0 (control), 25, 37 or 49 mg/mL.
• The extenders with various mannose concentrations were evaluated at 20 degrees C or 5 degrees C for different durations – 0, 12, 24, and 48 hours post-dilution.
• Five stallions of proven fertility were used for the measures, and each measure was repeated three times.
• In the second experiment, two groups of mares were inseminated with sperm extended in a traditional skim milk (control) extender or a 37 mg/mL mannose extender preparation. The pregnancy rate after a single cycle was compared in both groups.

Key Findings

• High concentrations of mannose in the extender affected progressive motility beyond the time and temperature effects noted in the controls.
• An extender containing only mannose (49 mg/mL) showed an immediate decrease in motility compared with the controls.
• The 37 mg/mL mannose extender had a less dramatic decrease in motility, but the decrease was noticeable after storage at 5 degrees C for longer than 12 hours.
• The extender with 25 mg/mL mannose performed similarly to the control formulation under all conditions.
• In the second experiment, both the traditional extender and the 37 mg/mL mannose extender achieved a 72% pregnancy rate in a single cycle.
• The study suggests that a semen extender containing up to 37 mg/mL mannose could maintain motile spermatozoa for on-farm use, and 25 mg/mL mannose concentrations preserved motility during long-term cooling.
• The sperm extended with up to 37 mg/mL mannose was found to have similar fertilizing capability as sperm in traditional extenders.