Dietary supplementation of selenium and addition of vitamin C and E in extender to enhance semen cryopreservation and reproductive performance of Saanen goats

Abstract

The present study investigated the effects of antioxidants supplementation, freezing extenders, cooling rates and equilibration times on Saanen buck reproductive performance and post-thaw sperm quality. For this reason, selenium was supplemented orally to evaluate its antioxidative potential on reproductive performance as well as on cooled and frozen-thawed semen. The effects of cooling rates, and different extenders were also investigated on post-thaw sperm quality. This was followed by the addition of vitamin C, E and their combination vitamis (C+E) to freezing extender to evaluate their effects on the cooled and post-thaw sperm motility and kinematic parameters post-thaw in relation to equilibration time. Selenium is an integral part of glutathione peroxidase (GSH-PX), an enzyme which protects cell internal structures against free radicals and is an antioxidant for cellular membrane lipids. Its deficiency has been reported to cause impaired motility, reduced fertility and sperm production. In the present study dietary Se supplementation increased testes measures, semen attributes and hormone concentrations of Saanen buck. Therefore, Se supplementation is recommendable, especially for animals depending on Se deficient Lucerne diets or pastures, to boost their natural antioxidants and enhance the ability of the seminal plasma to fight oxidative stress (OS). Although Saanen buck reproductive performance and fresh semen characteristics were improved with supplementation of Se, semen cooling and freezing is still a big concern due to excessive production of reactive oxygen species (ROS), leading to structural damage of sperm membranes. The suitable extenders, proper cooling rate and equilibration time are key elements to develop suitable protocol of semen cryopreservation. In this regard, a study was conducted to investigate the interactions between cooling rates (slow and fast) and freezing extenders: clarified egg yolk (CEY), whole egg yolk (WEY) and tris without egg yolk (TWEY) on post-thaw sperm quality in relation to dietary Se supplementation. The study revealed that the combination of clarified egg yolk (CEY) and slow cooling yielded higher percentages of cooled and frozen-thawed sperm characteristics of semen from Se supplemented bucks. This indicted that, supplementing animals with Se prior to the semen freezing process and using clarified egg yolk (CEY) in combination with slow cooling could be recommended for buck semen cryopreservation. Further to these results another study was conducted to determine the effects of both dietary selenium supplementation and addition of vitamin C (5 mM), E (4.8 mM) and their combination vitamins (C+E) to freezing extender as well as equilibration times (2, 4 and 6) on post-thaw sperm motility and kinematic parameters. Antioxidants supplementation prior to semen freezing led to higher post-thaw sperm motility and kinematic parameters when 2 or 4 h equilibration time was used. It can be concluded that the use of dietary selenium or the addition to extender of the combination of vitamins (C+E) as antioxidants agents, associated with optimum equilibration time, may protect better spermatozoa against free radicals during semen cryopreservation. In general, the different experiments conducted in this thesis revealed that supplementing bucks with selenium, and the addition of the combination of vitamins (C+E) to clarified egg yolk (CEY) extender together with slow cooling and 2 or 4 h equilibration period, can be an alternative option to enhance reproductive performance and post-thaw sperm motility and velocity parameters.