Effect of glycerol on motility, viability, extracellular aspartate aminotransferase release and fertility of stallion semen before and after freezing.

This study explores the impact of varying glycerol concentrations on the motility, viability and enzyme release of stallion sperm cells before and after deep freezing. The results suggest that while glycerol can partly preserve these attributes during freezing, its inclusion notably reduces fertility rates.

Understanding Glycerol’s Impact on Stallion Sperm Cells

The researchers have primarily delved into three aspects concerning the effect of glycerol on stallion sperm:

• Motility:
• Viability:
• Aspartate Aminotransferase (AST) release:

Sperm Motility and Viability

The motility and viability of the spermatozoa were not affected by the inclusion of glycerol. This observation was maintained when glycerol was incorporated in the TRIS-fructose-egg yolk diluent used for stallion semen extension, with no discernible changes in these two parameters. However, when the semen was deeply frozen, the sperm’s motility and viability were only partially persevered.

Aspartate Aminotransferase Release

During the experiment, the researchers also found no increase in AST release with the addition of glycerol. AST is an enzyme that can indicate cell damage, and its release can suggest potential harm to the sperm cells. Therefore, glycerol does not seem to damage stallion spermatozoa, at least in terms of causing increased AST release.

Effect on Fertility Rate

A fertility trial was conducted wherein semen was concentrated by centrifugation and then an extender with 7.5 per cent glycerol was added. Despite this, fertility was hardly affected, with a 70 per cent conception rate in 10 mares after one service period. Nevertheless, the research showed that the freezing and thawing of horse spermatozoa, even when 7.5 per cent glycerol was present, significantly decreased the fertilization rate. This implies that the process of freezing and thawing may do potential damage to the sperm’s fertility potential, which glycerol does not fully mitigate.