Case-control study of late-term abortions associated with mare reproductive loss syndrome in central Kentucky.

The research article investigates the factors influencing late-stage abortions in mares due to mare reproductive loss syndrome (MRLS) finding that more time in the pasture and less time in a stall, along with other environmental and dietary factors, increase the likelihood of these abortions.

Study Design and Approach

• The research is a case-control study, where one group presents a condition (in this case, late-term abortions in mares due to MRLS), and the other is a control group without the condition. A total of 282 broodmares from 62 farms in central Kentucky were included in the study.
• The mares were divided into three categories: 137 mares that had late-term abortions (LTAs) associated with MRLS, 98 mares from the same farms that didn’t abort, and 48 mares that aborted for reasons other than MRLS.
• Farm managers were interviewed to gather data about the mares’ lifestyle, management practices, and environmental exposure.

Findings

• Data from these categories of mares were then compared to identify risk factors influencing the occurrence of MRLS-associated LTAs (MRLS-LTAs).
• Several factors were identified as increasing the risk of mares having MRLS-LTAs. These factors include an increased amount of time grazing at pasture, decreased time housed in stalls, and feeding practices such as feeding concentrate on the ground or feeding in the pasture exclusively in the 4-week period before abortion.
• Additional risk factors are linked to water consumption: access to pasture after midnight during the four weeks prior to abortion, drinking from a water trough, and not having access to water buckets or automatic waterers.

Conclusion

• The analysis implies that higher exposure to the pasture predisposed mares to experiencing MRLS-LTAs and birthing stillborn foals.
• The authors suggest that practices limiting exposure to pasture — such as keeping mares in stalls for longer durations — could reduce the risk of MRLS-LTAs, particularly under environmental conditions similar to those experienced in 2001.