Case-control study of factors associated with excessive proportions of early fetal losses associated with mare reproductive loss syndrome in central Kentucky during 2001.

OBJECTIVE To identify factors associated with excessive proportions of early fetal losses associated with mare reproductive loss syndrome in central Kentucky during 2001. DESIGN Case-control study. PROCEDURE Questionnaires were used to collect information on farm-, pasture-, and individual animal-level factors purportedly associated with mare reproductive loss syndrome. Data were collected for 133 farms (97 with excessive proportions of early feta losses and 36 control farms) representing 6,576 mares. RESULTS Factors significantly associated with an increased risk of excessive early fetal losses were exposure to moderate to high concentrations of Eastern tent caterpillars, exposure to cherry trees, farm size > or = 50 broodmares, being bred during February 2001, and frequent exposure to waterfowl. Feeding hay to mares outside was associated with a decreased risk of excessive proportions of early fetal losses. Pasture composition and management factors were not significantly different between affected and control pastures. Individual animal-level factors were investigated on 6 farms representing 340 mares, and age, parity, and pre- and postbreeding treatments were not significantly associated with risk of early fetal loss. CONCLUSIONS AND CLINICAL RELEVANCE Results suggest that limiting exposure to Eastern tent caterpillars and cherry trees and feeding hay to mares outside may help decrease the risk of excessive proportions of early fetal losses associated with mare reproductive loss syndrome.