There was some apprehension in Central Kentucky as to whether the elimination of cherry trees and spraying for caterpillars would be enough to decrease the numbers of mare reproductive loss (MRLS) abortions that occurred in 2001, and to a lesser degree in 2002. The removal of the cherry trees to eliminate the most suitable habitat for the Eastern tent caterpillar (ETC) moth to lay her eggs, spraying trees to kill the caterpillars when the trees could not be removed, and the natural cycle of the ETC to die off after peak concentration years have all affected the concentration of caterpillars in 2003.
In 2001, a very high percentage of February and early March bred mares resulted in MRLS abortions (greater than 50%). In 2002, some farm management controls were put in place which resulted in a much lower percentage of abortions in the February and early March bred mares (less than 10%).
Research trials completed in spring of 2002 indicated that the ETC was indeed involved in the MRLS abortions. In the breeding season of 2003, strict precautions to remove pregnant mare exposure to the ETC in the entire Central Kentucky area resulted in a miniscule MRLS loss in the February- and March-bred mares. Any loss that was a MRLS suspect abortion was related to difficulty in completely eliminating exposure to the ETC.
In a recent poll of 2,037 mares examined at 60 days of gestation by area veterinarians, only 16 mares were not carrying a viable fetus. Six of these were suspect MRLS abortions.
- 2001–February and early March bred mares greater than 50 % aborted from MRLS;
- 2002–February and early March bred mares