Superior Post-Thaw Sperm Quality and Fertility of Epididymal Compared with Ejaculated Sperm in Subfertile Stallions

Despite the benefits of seminal plasma during breeding, its value is questionable when utilizing biotechnological approaches such as artificial insemination. In addition, deleterious effects of secretions from accessory glands on sperm viability and conception rate have been reported, especially in stallions with poor semen quality.

The present study aimed to compare the kinetics, structural and functional viability, and fertility parameters of spermatozoa obtained from the ejaculate and from the cauda epididymis of subfertile stallions, as well as to evaluate the differences in the electrolyte composition of the seminal plasma of animals with high versus low fertility.

The kinetic parameters of the sperm samples were evaluated by computerized analysis (CASA, HTM IVOS, Hamilton Thorne Research) and the plasma membrane integrity, acrosomal integrity, sperm membrane peroxidation, DNA fragmentation, sperm capacitation, membrane phosphatidylserine translocation, and caspase activation by flow cytometry analysis.

After thawing, epididymal sperm from subfertile stallions exhibited better sperm kinetics, structural and functional viability, and fertility than ejaculated sperm. Sodium concentration in seminal plasma was higher in subfertile than in fertile stallions.

These findings support a potential association between the seminal environment and sperm function in subfertile stallions, although the specific contribution of seminal plasma and the components involved remain to be determined.