This study sought to evaluate the effects of irradiating pig seminal doses with red LED light irradiation on their quality and longevity over liquid-storage at 17 °C. For this purpose, boar ejaculates were diluted in a commercial extender at a final concentration of 3 × 107 sperm/mL and stored at 17 °C for 96 h. Upon arrival to our laboratory (5-6 h within collection), 1.5 mL-aliquots were subjected to irradiation with a temperature-controlled red light-emitting diode (LED) for 1 min, 5 min or 10 min. Controls consisted of non-irradiated spermatozoa. Aliquots were then stored at 17 °C for 96 h, and plasma membrane and acrosome integrity, motility and free cysteine radicals of sperm head proteins were evaluated every 24 h. In addition, the sperm resilience to withstand thermal stress following irradiation was evaluated at 24 h, 48 h, 72 h and 96 h by incubating stored seminal doses at 37 °C for 120 min. In our experimental conditions, light-stimulation for 5 min and 10 min counteracted the decrease in thermal stress observed in non-irradiated samples during the first 48 h of storage. Moreover, all irradiation protocols counteracted the decrease in percentages of spermatozoa with altered acrosomes observed in non-irradiated samples after 72 h of storage. The effects of light-stimulation upon sperm motility parameters were less consistent. While liquid-storage also led to an increase in the free cysteine levels of sperm head proteins, this increment was partially mitigated through light-stimulation for 5 min and 10 min. Our results suggest that effects linked with red LED light irradiation would be consistently maintained in our experimental conditions for the first 48 h. Finally, the maintenance of light effect appears to depend upon the specific experimental design, the analyzed sperm parameters and the utilized irradiation patterns.
Keywords: Light-stimulation; Liquid-storage; Pigs; Semen preservation.
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