The results of a survey conducted by the University of Kentucky's Gluck Equine Research Center and College of Agriculture showed that a small number of Thoroughbred and other farms in Central Kentucky experienced an unusual increase in what is being termed fall fetal loss syndrome (FFLS). While there are "suspects," there is no definitive cause known at this time for the abortions which occurred in the last three months of 2002.
Detailed information on the breeding and management practices on eight affected farms (seven of which were Thoroughbred) and 22 farms that did not have FFLS (termed control farms) were evaluated, said Dr. David Powell of the Gluck Equine Research Center. Veterinarians and farms were very cooperative in gathering this information, he said.
Farms that had FFLS experienced abortions ranging from five to 22 per farm occurring between Sept. 1 and Nov. 30 (the cutoff on the survey). In some instances, the abortion was preceded by vaginal discharge. The fetuses were between 120 to 260 days of gestation. There were no significant pathologic changes seen during necropsy of the aborted fetuses at the Kentucky Livestock Disease Diagnostic Center (LDDC), said Powell.
Three risk factors were considered significant when the information was studied. Those were the use of a topical insecticide(s); caterpillars on the farm in 2001 and 2002 coupled with mare reproductive loss syndrome (MRLS) in the spring of 2002; and illness in some mares in 2002.
Suspects for causing the FFLS at this time include West Nile virus, other biologic agents, MRLS, endophyte toxicity, and insecticide toxicity. "We can't exclude the possibility that this is a chronic consequence of MRLS or exposure to caterpillars," said Powell. "Just as with MRLS, we've got to keep an open mind and not let individual theories bias our interpretation of what is going on."
On three of the eight farms with higher losses, pastures were examined. High levels of the ergot alkaloid associated with fescue toxicosis was found in those pastures. However, said Powell, a search of literature did not show any data that fescue could cause mid-term losses in cattle or mares. Weather information from the UK Agriculture Weather Center showed that a serious drought occurred in Central Kentucky from June through early October. "It is well-known that in drought conditions, fescue survives well," noted Powell. "In a number of pastures with losses, fescue was the predominate grass available to grazing mares. This doesn't prove that fescue was a factor in causing losses, but, we consider it worthy of pursuing."
"What we determined was that we are looking at a problem that was restricted to a small number of farms," explained Powell. "Further losses were experienced on these farms, and other farms were found to have losses, but it was a cluster on a small number of farms, the majority of which have been identified and participated in the survey."Kentucky Survey Provides Population Information
The fall 2002 survey of farms that did and did not suffer abortions from fall fetal loss syndrome gave important breeding information to Dr. David Powell and his colleagues from the University of Kentucky. The survey information allowed them to determine that on the 22 control farms, a year-end pregnancy rate of 90.5% was achieved. On seven of the eight farms with FFLS that provided complete information, the pregnancy rate was 75%.
"This is one of the first times we've obtained pregnancy rate data relevant to the current breeding season," said Powell.
This information is considered the "denominator" in trying to determine if a problem is significant in a population of pregnant mares. It is hoped that continued collection of this type of information will help researchers know if certain factors--such as an increase from last year in the number of abortions sent to the Kentucky Livestock Disease Diagnostic Center--is significant or just a reflection of the mare population and possibly increased submissions from breeders who previously didn't take fetuses to the lab.