Effect of heterologous and homologous seminal plasma on stallion sperm quality.

This research aims to understand how different types of seminal plasma (SP), either from the same stallion (homologous) or from a different one (heterologous), affect the quality of stallion sperm, with a particular focus on sperm motility and chromatin damage. The research found that adding seminal plasma can have variable impacts on these measures, and that the optimal combination of sperm and seminal plasma can be stallion-specific.

Research Purpose and Methodology

• It is noted that although most of the seminal plasma is usually removed from stallion semen to improve their survival during cooling storage, adding small quantities can possibly improve pregnancy rates or the survival rate of sperm cells during freezing and thawing (cryosurvival).
• Whether the seminal plasma from the same stallion (homologous) or that from a different stallion (heterologous) provides better effects is the subject of controversy. This may be due to the variations between stallions in seminal plasma proteins, or due to potential remnants of homologous seminal plasma in the sperm preparation.
• This study uses colloid centrifugation to allow for complete removal of the seminal plasma from stallion spermatozoa. By doing so, the researchers could then add back different seminal plasmas and observe the effects on the sperm cells.

Results and Findings

• The study found that adding seminal plasma had a minor but significant positive effect on sperm motility. However, it didn’t affect the proportion of spermatozoa that underwent the “acrosome reaction”, a crucial step that allows sperm to penetrate and fertilize an egg.
• Both types of seminal plasma, homologous and heterologous, yielded similar results in terms of sperm motility. There was considerable variation between different stallions’ sperm responses to different seminal plasmas, making it challenging to definitively say which type generally produces the best motility.
• Moreover, most stallions’ seminal plasma increased the production of reactive oxygen species and caused chromatin damage, negatively impacting sperm health and quality. These harmful effects were attributed to an observed increase in hydrogen peroxide production.

Conclusions and Recommendations

• In conclusion, the effects of seminal plasma on spermatozoa depend not just on the type of plasma (homologous or heterologous), but also on the specific pairing of plasma and sperm. This could be specific to a particular stallion.
• The researchers suggest that if adding seminal plasma is deemed necessary, it should be done right before insemination rather than before storage due to its potential detrimental effects like increased hydrogen peroxide production and sperm chromatin damage.