Tropical summer induces DNA fragmentation in boar spermatozoa: implications for evaluating seasonal infertility

Abstract

Summer infertility continues to undermine pig productivity, costing the pig industry millions in annual losses. The boar’s inefficient capacity to sweat, non-pendulous scrotum and the extensive use of European breeds in tropical conditions, can make the boar particularly vulnerable to the effects of heat stress; however, the link between summer heat stress and boar sperm DNA damage has not yet been demonstrated. Semen from five Large White boars was collected and evaluated during the early dry, late dry and peak wet seasons to determine the effect of seasonal heat stress on the quality and DNA integrity of boar spermatozoa. DNA damage in spermatozoa during the peak wet was 16-fold greater than during the early dry and nearly 9-fold greater than during the late dry season. Sperm concentration was 1.6-fold lower in the peak wet than early dry whereas no difference was found across several motility parameters as determined by computer-assisted sperm analysis. These results demonstrate that tropical summer (peak wet season) induces DNA damage and reduces concentration without depressing motility in boar spermatozoa, suggesting that traditional methods of evaluating sperm motility may not detect inherently compromised spermatozoa. Boar management strategies (such as antioxidant supplementation) need to be developed to specifically mitigate this problem.

Seasonal Changes of Nuclear DNA Fragmentation in Boar Spermatozoa in Spain

“…This could produce a bias in the study because the bad ejaculates according to these criteria were systematically discarded for the DFI test thus differences between seasons could be hidden. Peña et al (2019) [14] evaluated the influence of Australian seasons (early dry, late dry and wet peak) on sperm DFI from five large white boars. BTS-diluted semen samples were purified by Percoll gradient centrifugation to discard possibly dead and damaged spermatozoa before being analyzed by TUNEL.…”

“…The sperm chromatin stability assay (SCSA) is a simple test that assesses sperm nuclear chromatin status by flow cytometry using acridine orange (AO) fluorochrome [12]. Boar sperm nuclear DNA is normally highly condensed and stable; the SCSA detects the abnormal chromatin structure and potential DNA damage that depends on the susceptibility of DNA to denaturation [13,14]. The results obtained from the SCSA are not correlated with other conventional semen parameters and can be considered an independent parameter [15].…”

“…Contrarily, Petrocelli et al (2015) [27] reported that season, photoperiod or genetic line did not affect sperm nuclear DNA fragmentation. However, Peña et al (2019) [14] described that a tropical summer induces nuclear DNA damage and reduces sperm concentration without depressing motility suggesting that traditional methods of evaluating sperm motility may not detect inherently compromised spermatozoa.…”

Antioxidative Defense and Fertility Rate in the Assessment of Reprotoxicity Risk Posed by Global Warming

“…Moreover, studies on elevated scrotal temperature in Mammalia, such as the house mouse Mus musculus testes [22,24,139], and in the pig Scrofa domesticus [114], showed how high temperature can lead to severe genetic and morphological damage. In fact, scrotal heat significantly induces DNA fragmentation in germ cells and spermatozoa, alters epididymal structure and epididymal sperm maturation, reduces the relative testis weight, and impairs steroidogenesis and lipid droplet accumulation observed in Leydig cells in mouse.…”

Period of Boar Ejaculate Collection Contributes to the Yearly Intra-Male Variability of Seminal Plasma Cytokines

“…The study was conducted in European pigs, a species of mammal that is generally not considered reproductively seasonal, but still shows a tangible seasonal reproductive pattern [38]. This seasonal pattern has been well documented in breeding boars, influencing sperm production and quality [39][40][41][42][43]. The four seasons of the year in temperate geographic areas, namely winter, spring, summer, and autumn, are environmentally mainly characterized by differences in daylight and in air temperature.…”