A retrospective case-control study of pregnancy failure in Thoroughbred horses in Australia.

This research paper is a study of the factors affecting pregnancy failure in Thoroughbred horses in Australia, finding an incidence risk of 5.4 failures per 100 45-day pregnancies and potential links to lack of vaccination against Salmonella and environmental aspects.

Introduction and Methodology

• The primary objective of this study was to examine and evaluate the incidence and risk factors associated with pregnancy failure in Thoroughbred horses, an issue identified as economically significant and detrimental to animal welfare within the industry.
• The researchers undertook a retrospective, nested, case-control study focusing on resident mares on studs located in the Hunter Valley, Australia, during the period of 2021-2022.
• The study was split into three periods of gestation: early (46-150 days), mid (151-270 days), and late (>270 days) to examine the rate of pregnancy failures in each period.

Key Findings

• The research indicated an annual incidence risk of 5.4 pregnancy failure cases per 100 45-day pregnancies, equating to 0.05 cases per mare.
• Full-term or perinatal losses (pregnancies of 320 days or more) constituted 24% of all cases of pregnancy failure.
• The study showed that there were no discernible differences in pregnancy failure rates based on the age of the mare or their reproductive history.

Significance of Findings

• One of the key revelations of the study was that control mares, those not experiencing pregnancy failure, were six times more likely to have been vaccinated against Salmonellosis (a bacterial disease caused by Salmonella) than the case mares. This suggests a strong correlation between lack of vaccination and pregnancy failure.
• Another contributing factor to pregnancy failure was environmental, with paddocks containing native trees being associated with an increase in losses.
• The study lends support to the idea that Salmonella might be a crucial cause of pregnancy failures in Thoroughbred horses in Australia.
• The results of the study contribute to the fundamental data needed for the development of targeted surveillance strategies for pregnancy failure in Australian Thoroughbreds, which can potentially benefit the industry economically and from a welfare perspective.
• The authors of the paper underscore the need for ongoing research into factors like the role of Salmonella in pregnancy failure to improve breeding success rates and the general welfare of Thoroughbred mares in Australia.