LEVELS OF FUMONISIN-B1 AND FUMONISIN-B2 IN FEEDS ASSOCIATED WITH CONFIRMED CASES OF EQUINE LEUKOENCEPHALOMALACIA

Leukoencephalomalacia (LEM) is a neurotoxic disease of Equidae caused by the ingestion of feed contaminated with the fungus Fusarium moniliforme. Feed samples from the United States that were fed to horses prior to the development of LEM were analyzed for fumonisin B1 (FB1) and fumonisin B2 (FB2), toxic secondary metabolites of F. moniliforme. In addition, FB1, FB2, and moniliformin were determined in corn cultures of 10 isolates of F. moniliforme from these samples. None of the cultures produced moniliformin but all contained both FB1 (160-3800-mu-g g-1) and FB2 (20-950-mu-g g-1). All 14 feed samples contained both FB1 (1.3-27.0-mu-g g-1) and FB2 (0.1-12.6-mu-g g-1). FB1 was the major fumonisin in the cultures (80-96%) as well as in the feed samples (53-93%). These results support the finding that the fumonisins are causative factors in the development of LEM in horses.