Egg yolk plasma enriched with β-carotene through the diet of laying hens and adding it to the extender improves the quality of frozen semen in Arabic stallions

Equine semen cryopreservation is one of the major procedures for the genetic conservation of rare and endangered genotypes. The current study was conducted to evaluate the effect of egg yolk plasma (EYP) enriched with beta-carotene as an antioxidant supplement on INRA-96 extender regarding freezing Arabic stallion sperm. For this purpose, beta-carotene various concentrations were utilized as a supplementary ingredient in formulating the diets of laying hens. Birds were randomly divided into four groups, fed with 0 (control), 500, 1000 and 2000 mg/kg in a supplemented diet with beta-carotene. Subsequently, various variants of enriched extender (INRA-96 + 2.5% glycerol [G]) were gained by adding 2% EYP from four treatment groups. The sperm characteristics, including motility, viability, morphology, plasma membrane integrity (HOS test), lipid peroxidation (MDA) and DNA fragmentation, were evaluated after thawing. According to the results obtained in this study, the addition of EYP from T-2 and T-4 (500 and 2000 mg/kg of beta-carotene in hens' diet) to the extender (INRA-96 + 2.5% G) leads to an increase in total motility (50.50% and 49.49%, respectively), progressive motility (32.6% and 31.8%, respectively), viability (68.7% and 66.1%, respectively) and plasma membrane integrity (57.7% and 50.6%, respectively). Moreover, lipid peroxidation (1.3 and 1.4 nmol/mL, respectively) and DNA fragmentation (8.6% and 9.9%, respectively) were diminished using the mentioned treatments. However, sperm morphology was not affected by the treatments. In the current study, we concluded that the optimal concentration of beta-carotene in the laying hen's diet (500 mg/kg) could reveal the best results about sperm quality. So, EYP enriched with beta-carotene acts as a valuable natural and safe supplementary material that could be exploited for enhancing stallion sperm quality in cryopreservation conditions.