Effect of Seminal Plasma Components on the Quality of Fresh and Cryopreserved Stallion Semen

The importance of seminal plasma (SP) components for stallion semen quality and freezability is little known. This study aimed to evaluate the relationship between SP components and fresh/cryopreserved stallion semen quality. Semen of 30 stallions was collected, and then, SP was recovered and lyophilized. Total protein (TP), vitamin C (CVIT), vitamin E (EVIT), vitamin A (AVIT), iron (Fe), copper (Cu), magnesium, and zinc (Zn) in SP were assessed. Sperm was frozen in an extender supplemented with lyophilized SP. In fresh semen motility, abnormal morphology (AM), sperm vitality (SV), and plasma membrane integrity (PMI) were evaluated. In post-thaw semen, additionally, total motility (TM), progressive motility (PM), straight line velocity (VSL), curvilinear velocity (VCL), average path velocity (VAP), amplitude of lateral head displacement (ALH), and beat cross-frequency (BCF) were assessed. Levels of component of SP were established by a distribution analysis. Generalized linear models were fitted. Comparisons of means were done with Tukey's test. Correlation and regression analyses were performed. Vitamins and ions were found to be related to fresh semen quality. For post-thaw sperm, medium TP showed higher semen quality. Negative regression and correlation coefficients between CVIT and all post-thaw semen parameters were found. Low EVIT yielded the lowest PM, VSL, and VAP values, while a high level of AVIT yielded the best results for sperm quality. A high level of Cu yielded higher results for TM, PM, VCL, and ALH. Moreover, a negative correlation was found between Zn, SV, and PMI. In conclusion, SP composition influences fresh and post-thaw stallion semen quality.