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Mare Reproductive Loss Syndrome Index Page

May 3, 2002


Field reports from farm managers and equine practitioners attending the Equine Industry Task Force meeting Thursday evening, May 2nd appear to strongly support preliminary research results released by the University of Kentucky College of Agriculture on Wednesday. The preliminary research results indicate an elevated level of foal loss in mares on pasture exposed to eastern tent caterpillars (ETC) or the insects’ waste or frass.

At this time the Equine Industry Task Force is confident in reporting that where ETC concentrations are low in the field, fetal losses are minimal and within normal range. Therefore the task force continues to strongly recommend that horse farms manage and minimize exposure of pregnant mares to eastern tent caterpillars and their frass.

Dr. Tom Riddle, equine practitioner with Rood & Riddle Equine Hospital, reported findings  based upon ultrasound examinations of 103 mares with pregnancies of 42 days or greater between April 26 and May 2, 2002. Riddle’s findings showed 5 fetal losses. During a similar time period in 2001, examination of 69 mares at the same stage of pregnancy, showed 9 fetal losses. This represents a 62% reduction in fetal losses in 2002 compared to 2001.

Dr. Stuart Brown, equine practitioner with Hagyard-Davidson-McGee Associates, reported that although he is seeing evidence of MRLS fetal losses in the field, there is a significant reduction overall in the incidence as compared to last year.

Dan Rosenberg reported that 106 mares boarding at Three Chimneys Farm with pregnancies over 40 days were rechecked for pregnancy this week and all remain in foal.

Taylor Made Farm has checked 97 mares with pregnancies of 59 days or greater and reports no losses attributed to MRLS in 2002.  Through the same time period in 2001, ultrasound check of 74 mares with pregnancies of 59 days or greater revealed 25 losses or 34% empty mares.

On some farms, mares on fields with heavier populations of ETCs are reported to have higher than normal fetal losses which appear to be consistent with MRLS. At this time, losses do not appear to be widespread, appear to be associated with heavy populations of ETCs and are significantly less overall than last year.

Ryan Conboy
Kentucky Thoroughbred Association, Inc.

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