Unlocking the Secrets of Thoroughbred Pregnancy Success
The world of horse breeding is a delicate dance, and one of the most critical steps is ensuring a healthy pregnancy. But what happens when a mare loses her pregnancy? This is a pressing issue that affects the entire industry, and it's time to delve deeper into the factors at play.
AgriFutures Australia's Thoroughbred Program is taking a bold step forward with a multi-stage project titled 'The pathology and epidemiology of equine pregnancy loss.' The goal? To unravel the mysteries behind abortion in mares and, in doing so, improve the nation's foal crop.
Navigating the Risks
Despite a decline in the number of Thoroughbred mares covered over the last two decades, the percentage of live foals born has been on the rise, thanks to advancements in reproductive science and management. According as to the Australian Stud Book, this percentage has hovered around 65% for the past five seasons.
Breeding is an expensive and time-consuming process, and reducing risk factors in the mare's environment is crucial for better outcomes. While the risks from birds, bats, and caterpillars are well-known, the question remains: when is a mare most vulnerable during her pregnancy, and what factors increase her exposure?
Uncovering Regional Differences
The answer to this question varies by region, which is why AgriFutures Australia initiated a comprehensive research project in 2020. The first stage focused on the Hunter Valley, analyzing data from a breeding season and subsequent pregnancies to identify the leading causes of pregnancy loss and their distribution.
Dr. Joan Carrick, an expert in perinatal foal pathology and high-risk pregnancy management, sheds light on the project's significance: "There wasn't much known about the epidemiology of pregnancy loss. It can differ significantly from farm to farm and year to year. We conducted this study to enhance our understanding of when and where losses occur and their impact on farms."
Environmental Factors: A Key Piece of the Puzzle
The initial study, published in April 2025, examined the 2021/22 season in the Hunter Valley. It went beyond just the mares' data, exploring their environment, biosecurity, pest control, and feeding practices. A crucial finding was that control mares (those who didn't experience pregnancy loss) were six times more likely to be vaccinated against salmonella, and environmental factors played a significant role in abortion rates.
"We gathered data on the paddocks the mares were kept in, including tree types, pasture, water sources, fencing, and proximity to roads and bushland," Dr. Carrick explained. "Mares in less manicured paddocks in the central areas of the farm were more likely to abort. This could be because studs closely monitor these mares, but more data is needed to confirm this."
Mapping Environmental Influences
Paddocks with non-native tree lines or well-fenced trees were less likely to have mares that aborted during the study. Similarly, proximity to staffed buildings or roads seemed to reduce the risk. This finding highlights the need to investigate further the relationship between environmental elements and pregnancy loss causes.
Another study under the same project analyzed fetal loss submissions in the Hunter Valley from February 2015 to November 2021, revealing patterns in pregnancy loss causes. Combining these findings with environmental data provides a clearer understanding of abortion factors.
Dr. Carrick emphasizes the importance of environmental data: "If we find similar patterns with the environment, we need to ask what specific aspects of those paddocks and mare management contribute to abortion. Environmental information is unique and challenging to collect, but it's vital to seeing the full picture."
Regional Trends and Patterns
The ongoing study, starting in 2025, is repeating the research across the Hunter region and expanding to Queensland studs. Dr. Carrick stresses the importance of regional variations: "Each region has its unique trends. Expanding to Queensland is essential due to its distinct environment and climate from the Hunter Valley. For instance, a UK study showed that mares with late cover dates or multiple serves are more likely to lose pregnancies, but we need to confirm if this holds true in Australia."
Repeating the study in the Hunter will enable researchers to build upon previous findings and identify any changes in patterns.
"Collecting data annually is valuable for comparing patterns and trends over time," Dr. Carrick notes. "I've observed outbreaks' patterns for 25 years, and understanding these variations is crucial."
A Roadmap for the Future
The current study aims to build upon existing data and develop strategies to minimize identified risks. Dr. Carrick expresses gratitude to participating studs and looks forward to analyzing the data by mid-February.
Breeders in Queensland will have access to information about pregnancy losses in their region, helping them understand local factors, the number of losses, and when they occur. This knowledge will enable breeders to allocate resources more efficiently during high-risk periods.
Dr. Carrick emphasizes the value of every pregnancy: "Every pregnancy is valuable, and breeders work hard to ensure their success. If a pregnancy is compromised, it can lead to long-term health issues for the foal and impact its athletic potential. Organ development, especially the heart and lungs, is crucial for breeders aiming to produce racehorses."
AgriFutures Australia has released resources to prepare and manage mares during abortion season.
The research aims to improve the covers-to-live-foals ratio by supporting more pregnancies to full term. Dr. Carrick's vision is clear: "We strive for every pregnancy to be healthy and result in a healthy foal. While genetic factors are beyond our control, understanding and minimizing environmental factors is key to reducing losses."
But here's where it gets controversial: Are there ethical considerations when it comes to managing high-risk pregnancies and potentially influencing a foal's long-term health? How do breeders balance the desire for healthy pregnancies with the genetic potential of the foals? Share your thoughts in the comments below!
