Background: Summer infertility due to heat stress significantly affects the reproductive potential of pigs causing over $300 million per year in lost productivity to the US pig industry and billions worldwide. The boar's inefficient capacity to sweat; non-pendulous scrotum, and the high susceptibility of boar sperm to temperature shock appears to correlate with higher sperm DNA damage during summer. Heat stress-induced sperm DNA damage can result in early embryo loss, as demonstrated in mice. This study investigated whether supplementing boars with antioxidants during summer could improve boar sperm DNA integrity.
Method: Motility of sperm obtained from n=5 Large White boars housed in the dry tropics of Townsville, Queensland, Australia were analysed using Computer-Assisted Sperm Analysis. Sperm DNA integrity during summer was compared without or after 42 and 84 days antioxidant supplementation, by Terminal deoxynucleotidyl transferase dUTP Nick-End Labelling and flow cytometry. Paired T-tests were used to determine significant differences between treatments (P ≤ 0.05).
Results and Discussion: Total and progressive motility of sperm did not differ between treatments (P ≥ 0.05). However, antioxidant supplementation of boars during summer resulted in a 38% and 55% reduction of DNA-damaged spermatozoa after 42 and 84 days treatment respectively (16.1 ± 4.8% untreated vs 9.9 ± 4.5% vs 7.2 ± 1.6%; P ≤ 0.05).
Conclusions: Supplementing boars with antioxidants during summer improves boar sperm DNA integrity which could potentially mitigate the negative impact of heat stress on male fertility. Such improvements may also increase downstream fertilisation rates and early embryo survival in the sow
