Revisiting summer infertility in the pig: could heat stress-induced sperm DNA damage negatively affect early embryo development?
Santiago T. Peña , Jr A B C F , Bruce Gummow C D , Anthony J. Parker E and Damien B. B. P. Paris B
+ Author Affiliations
- Author Affiliations
A College of Veterinary Medicine, Visayas State University, Baybay City, Leyte, 6521-A, Philippines.
B Discipline of Biomedical Science, College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Qld 4811, Australia.
C Discipline of Veterinary Science, College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Qld 4811, Australia.
D Faculty of Veterinary Science, University of Pretoria, Onderstepoort, 0110, South Africa.
E College of Food, Agricultural and Environmental Sciences, Ohio State University, Wooster, OH 44691, USA.
F Corresponding author. Email: santiago.pena@my.jcu.edu.au
Animal Production Science 57(10) 1975-1983 https://doi.org/10.1071/AN16079
Submitted: 23 July 2015 Accepted: 19 June 2016 Published: 24 August 2016
Journal Compilation © CSIRO Publishing 2017 Open Access CC BY-NC-ND
Abstract
Temperature is a crucial factor in mammalian spermatogenesis. The scrotum, pampiniform plexus, and cremaster and dartos muscles in mammals are specific adaptations to ensure sperm production in a regulated environment 4−6°C below internal body temperature. However, the limited endogenous antioxidant systems inherent in mammalian spermatozoa compounded by the loss of cytosolic repair mechanisms during spermatogenesis, make the DNA in these cells particularly vulnerable to oxidative damage. Boar sperm is likely to be more susceptible to the effects of heat stress and thus oxidative damage due to the relatively high unsaturated fatty acids in the plasma membrane, low antioxidant capacity in boar seminal plasma, and the boar’s non-pendulous scrotum. Heat stress has a significant negative impact on reproductive performance in piggeries, which manifests as summer infertility and results in productivity losses that amount to millions of dollars. This problem is particularly prevalent in tropical and subtropical regions where ambient temperatures rise beyond the animal’s zone of thermal comfort. Based on preliminary studies in the pig and other species, this article discusses whether heat stress could induce sufficient DNA damage in boar sperm to significantly contribute to the high rates of embryo loss and pregnancy failure observed in the sow during summer infertility. Heat stress-induced damage to sperm DNA can lead to disrupted expression of key developmental genes essential for the differentiation of early cell lineages, such as the trophectoderm, and can distort the timely formation of the blastocyst; resulting in a failure of implantation and ultimately pregnancy loss. Confirming such a link would prompt greater emphasis on boar management and strategies to mitigate summer infertility during periods of heat stress.
Additional keywords: boar, DNA fragmentation, embryo loss, seasonal infertility, spermatozoa, Sus scrofa domestica, temperature.
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