College of Agriculture
Veterinary Science	Mare Reproductive Loss Syndrome Index Page
Briefings

Mare Reproductive Loss Syndrome

Briefing, July 2

Briefing, July 2, 2001
Monday, 5:00 pm

Mare Reproductive Loss Syndrome
UK College of Agriculture

MRLS Update

Although the rate of early fetal loss and late term abortions has drastically declined, research has been actively ongoing.  Investigation into the possible role of mycotoxins, ergot alkaloids, phytoestrogens and chemical compounds including cyanide are being actively pursued.  They include the development of an ‘in house’ method for detecting cyanide and thiocyanates in animal samples. Test results for hemlock as well as nitrate/nitrite toxicity have so far proved negative.

The epidemiological survey was conducted by individual visits to participating farms to ensure the quality of data in the complex 11-page questionnaire.  Of the 150 farms initially contacted, 133 were able to participate.  This represents a 89% participation rate which is extremely high for scientific surveys.  Reasons for not participating included not having the time to compile the data due to horse showing events, sickness in the family, and having too few broodmares on the farm.

The 133 farms represent over 17,000 horses present on the premises as of April 1, 2001, and included Thoroughbred, Standardbred, American Saddlebred and Morgan horse farms.  These farms were located in multiple central Kentucky counties.

While surveys were being completed and logged, a computer program was developed to analyze this large amount of information.  Data was verified and entered as surveys were returned.  An in-depth analysis of this data is very detailed and is not a fast process.

However, preliminary analysis of pasture data has revealed several individual risk factors as they relate to reproductive loss.  Risk factors which were higher in pastures with affected mares versus pastures with low or no losses in mares include:

• Cherry trees in and around pastures;
• Cherry tree seedlings in the pasture;
• Deciduous trees stripped of leaves in pastures;
• Moderate to heavy caterpillar presence;

• Pasture composition of 40% or greater of any of the following grasses:  fescue, orchard grass, bluegrass, clover or other grasses;
• Clover at 10 or 20% in pastures;
• Chain harrowing;
• Feeding supplemental hay;
• Spring pasture fertilization;
• Presence of deciduous trees (non-cherry) in or around pastures;
• Surface water in pasture.

Other pasture factors are currently being studied, and results will be made available as soon as possible.  Farm management data will be forthcoming, and combinations of pasture/farm management risk factors that may predispose to increased reproductive losses will be examined and reported.