Evaluation of early fetal losses on four equine farms in central Kentucky: 73 cases (2001).

The research article is a study examining the factors that influence early fetal losses (EFL) in Thoroughbred broodmares in central Kentucky.

Study Summary

• The study performed was a retrospective one and it focused on analyzing the 2001 breeding records of 288 Thoroughbred broodmares.
• The main aim of the study was to identify the characteristics of an EFL syndrome and assess potential factors that could increase the risk of EFL in broodmares at four farms.
• The study defined early fetal loss as the loss of a fetus that was viable at 40 days of gestation or more but was later lost by the fifth month of gestation.

Results

• In 2001, the overall EFL rate stood at 25%, representing 73 out of the 288 broodmares. The medium age of gestation when the fetal loss happened was 77 days. Most losses happened in early May.
• There was a significant difference in the fetal loss rate across the four farms. One farm had significantly lower losses (5%) compared to the other three which faced higher losses ranging from 26% to 35%.
• Mares that were barren or maiden (young and inexperienced in breeding) had higher rates of losses at 42%, compared to mares that were foaling at 18%.
• The findings revealed that younger mares had a higher risk for EFL compared to older ones. As such, the mare’s age, the broodmare farm, and reproductive status were significant factors.
• However, there was no association found between EFL and the sire used for mating or the stud farm.

Conclusions

• The study found that the highest risk for EFL occurred in the period from late April to May, that corresponds to mares bred during February through March.
• It also suggested that differences in management and environmental factors might be influencing the outcomes, especially considering the higher incidence of EFL in maiden and barren mares and the lower EFL rate in one of the four farms.
• The identified risk factors that needed further investigation included environmental differences among farms and differences in management procedures used for lactating versus nonlactating mares.