Results of Farm Survey To Determine Autumn Fetal Loss Risk Factors

Results of a survey of central Kentucky horse farms has provided information on possible risk factors associated with increased fetal losses during early and late autumn 2002. The survey was conducted by the University of Kentucky Department of Veterinary Science in conjunction with other departments within the College of Agriculture.

Thirty farms filled out detailed questionnaires. Twenty-two of these were "control" farms which had reported no apparent increases in fetal losses, and eight farms were "affected" farms representing the small number with higher-than-normal autumn losses.

Following completion of questionnaires, veterinarians with the eight affected farms were interviewed to gain more details and insights useful for data interpretation.

"We received 100 percent cooperation from our farms and veterinarians, and that certainly contributed to increased accuracy and confidence in the findings," said Powell.

Of nine identified risk factors, four were determined to be significant enough to warrant closer study: (1) topical application of insecticides, (2) presence of Eastern Tent Caterpillars (ETC), (3) presence of MRLS, and (4) increased illnesses. High levels of ergot alkaloids associated with fescue endophyte toxicity were found on some farms, and both control and affected farms had used insecticides in 2002 to control ETC.

These data suggest the possibility of some potential "suspects" that may have contributed to increased losses: a chronic consequence of MRLS, fescue endophyte toxicity, insecticide toxicity, West Nile virus, or other biological agents.

"These are only suspects, and as such are innocent until further evidence is obtained," said Powell. "We should also emphasize we are dealing with a multi-factorial situation. There could be a combination of causes or other factors, such as weather, that could have played a role in the increased losses. We're still putting the puzzle together and must keep an open mind."

Powell noted the difficulty of studying an apparent increase in abortions when the total number of pregnant mares is not known.

"We don't have precise data on how many mares covered in 2002 were still pregnant at the end of the year, therefore itís difficult to determine if accessions as a percentage of total is significantly higher than previous years," he said.

Additional survey data provided information on the percentage of mares on participating farms that maintained their pregnancies during 2002. As of December 2002, the control farms had a 90.5 percent pregnancy rate of mares covered since February, compared to a 75 percent rate for affected farms.

The UK Department of Veterinary Science is continuing to post 2003 equine abortion accessions to its MRLS web site.

"We're continuing to post accessions to the Livestock Disease Diagnostic Center so that our equine industry is kept informed as we enter the spring foaling season," Powell said. "As in the past, it's important to look at these accessions in terms of possible trends that may occur over several weeks rather than a slight increase reported for a specific week."

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