Temporality of early-term abortions associated with mare reproductive loss syndrome in horses.

The research article is about a study conducted to understand the time-related aspects of early-term abortions in horses, especially in relation to mare reproductive loss syndrome (MRLS). The study found that horses bred before April 1, 2001, had significantly higher rates of early-term abortions, suspected to be due to an external cause of MRLS that likely occurred prior to this time.

Study Objectives and Methods

In this study, the researchers wanted to:

• Characterize the temporality, essentially the time-related aspects, of breeding and early-term abortions associated with MRLS.
• Identify the times of greatest risk for these abortions.

To achieve this, they used data from 2,314 mares confirmed pregnant approximately 28 days after breeding. These mares were from 36 farms in central Kentucky, and included 515 mares that had early-term abortions.

Farm veterinarians and managers provided data for each mare including pregnancy status, breeding date, the date the mare was last known to be pregnant, and date of abortion.

Study Findings

The study revealed several key findings:

• Mares bred prior to April 1, 2001, were at the greatest risk of early-term abortion, both within individual farms and across different farms.
• The highest risk period for abortion was among mares bred in mid-February, with a weekly estimated incidence rate of abortion of 66%.

Conclusions and Implications

The researchers concluded that:

• In central Kentucky, mares bred between mid-February and early March appeared to have the greatest risk of early-term abortion.
• The risk of abortions decreased gradually to a background incidence of around 11%.
• Mares bred after April 1, 2001, were at a significantly lower risk, suggesting that the cause of MRLS was likely exposed to the mares before this date.

This study highlights the importance of understanding the temporal patterns of MRLS associated abortions, which can aid in identifying at-risk periods and implementing preventive strategies. Overall, the potential exposure to the cause of MRLS seems to have a temporal relationship, underscoring the need for further investigations to identify and understand this causative agent.