Acrosin activity is a suitable indicator of boar semen preservation at 17 °C when increasing environmental temperature and radiation

The effect of increasing environmental temperature and radiation on the sperm quality and the field fertility of refrigerated seminal doses from AI boars (N = 30) was analyzed throughout four experimental months (from March through June). In each experimental month, analyses of sperm quality were performed at days 0, 1, 3, 5, 7, and 9 of refrigeration of seminal doses; pregnancy rate and litter size were evaluated using double monospermic inseminations of multiparous female animals using seminal doses at Days 1 to 2 and Days 3 to 4 of refrigeration. Sperm quality was assessed from the evaluation of conventional parameters of sperm concentration, sperm motility, sperm morphology, and sperm viability, and capacitation parameters of membrane lipid disorder, intracellular calcium content, and acrosin activity. Results showed that sperm quality of boar seminal doses was negatively affected by increasing temperature and radiation, which resulted in significantly decreased sperm motility and viability, acrosin activity, pregnancy rate, and litter size, and significantly increased intracellular calcium levels in the trials performed in June. In any experimental month, aging of refrigerated doses was associated with the progressive increase of intracellular calcium levels and inactivation of acrosin, that began from Day 5 of storage in the trials performed in March and April, from Day 3 in those of May, and from Day 0 in those of June. Among the sperm parameters analyzed, only acrosin activity exhibited a clearly differentiated pattern in association with increasing temperature and radiation, and a significant correlation with pregnancy rate and litter size. These results highlighted the potential role of acrosin activity as an indicator of boar sperm preservation at 17 °C in boars.