PhD Understanding, reducing the effects of heat stress on TB stallion fertility

Summary

Systemic heat stress in mammals is detrimental to sperm production and male fertility. However, this phenomenon has not been adequately examined in the horse, or in a field setting relevant to the Australian Thoroughbred industry. Specifically, we do not know how the climatic conditions experienced by stallions in the major Thoroughbred breeding hubs of Australia affect their fertility, nor can we predict how projected increases in temperature associated with climate change will affect the industry’s productivity in the future. Preliminary data obtained from NSW Hunter Valley studs clearly show a relationship between ambient temperatures and per cycle conception rates. We propose that heat stress is a major driver of subfertility in stallions via increased oxidative DNA damage in spermatozoa and subsequent embryo loss, as well as a possible cause for mutations and disease in offspring of affected stallions. We are seeking to further examine the relationship between ambient temperatures, sperm DNA damage and stallion fertility. Understanding these mechanisms is expected to yield several shortterm outcomes improving the reproductive efficiency of the Thoroughbred industry, with longerterm outlook for development of novel management strategies to alleviate the effects of heat stress on fertility. We hope to obtain the support of AgriFutures for the costs of living, relocation and accommodation for a PhD student to be stationed in the Hunter Valley, working closely with Thoroughbred stud farms to collect samples and analyse data in order to understand the impacts of heat stress on fertility and implement practical measures to improve reproductive outcomes.

Program

Thoroughbred Horses

Research Organisation

The University of Newcastle

Objective Summary

This project aligns closely with Objective 1 of the Thoroughbred horse breeding research priorities and seeks to improve productivity by understanding and alleviating the effects of heat stress on stallion fertility, as well as its potential to increase the risk of developmental disease in offspring through oxidative DNA damage in stallion spermatozoa. This project aims to answer the following questions: 1. Do ambient temperatures affect fertility of Thoroughbred stallions? 2. Do ambient temperature increases induce oxidative damage in stallion sperm DNA? 3. Which parts of the equine genome are most susceptible to heatstressinduced DNA damage? I.e. are these risk loci for diseases known to occur in the horse? 4. Can management measures be implemented to successfully alleviate the effects of heat stress on thoroughbred stallions? 5. Can an antioxidant supplement formulated to protect spermatozoa from oxidative stress be beneficial in susceptible animals?