55 SEMINAL PLASMA COMPONENTS AND THEIR RELATIONSHIP WITH STALLION SEMEN FREEZABILITY

Abstract

Oxidative stress has been identified as a major cause of low seminal fertility. Among the components of stallion seminal plasma, some enzymatic and non-enzymatic antioxidants have been identified, which protect sperm from injurious effects of reactive oxygen species (ROS); however, the characterisation of these components is still in preliminary stages, as well as their relationship with freezability. The aim of this study was to evaluate the effect of some components of seminal plasma (SP) on stallion semen freezability. Semen of 30 Colombian Creole horses, and a total of 60 ejaculates, were collected. Semen was centrifuged to recover the SP. It was lyophilized and some components were assayed: total protein concentration (TP) by Bradford assay, CRISP3 protein concentration by ELISA, vitamin C (CVIT), vitamin E (EVIT) and vitamin A (AVIT), by HPLC; content of iron (Fe), copper (Cu), magnesium (Mg) and Zinc (Zn) by atomic absorption spectroscopy flame. Semen was supplemented with 10% stallion lyophilized SP and cryopreservation was performed. Post-thaw, 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 using a computer-assisted sperm analysis (SCA^®, Microptic SL, Barcelona, Spain). Sperm viability (SV) was determined by the Live/Dead kit (Molecular Probes Inc., Eugene, OR, USA). Normal sperm morphology (NM) was performed by the supravital technique and plasmatic membrane integrity (MI) was evaluated by the hypo-osmotic test. For statistical analysis, completely randomised mixed models were fitted. Levels according to the concentration of components of SP (high, medium, and low) were established. Comparisons of the means between levels were done with Tukey’s test. The significance level used for all assessments was P < 0.05. Means for TP of 0.35 mg BSA/g, CRISP3 of 55.22 ng/mg, CVIT of 2.66 mg/g, EVIT of 72.36 µg/g, AVIT of 37.37 µg/g, Fe of 17.37 mg/kg, Cu of 33.64 mg/kg, Mg of 109.08 mg/kg, and Zn of 0.49 g/100 g of SP were found. We found that a high level of CRISP3, AVIT, Cu, and Fe had higher results for post-thaw TM, PM, NM; medium levels of TP and Mg showed higher post-thaw TM, PM, NM, and MI; and lower levels of Zn had better results for post-thaw TM, PM, VCL, and VAP. In contrast, high and medium levels of CVIT had a deleterious effect on post-thaw TM, PM, SV, NM, and MI. We concluded that there is a relationship between concentrations of seminal plasma components and stallion semen freezability.