To examine the effects of acute exposure to fumonisin-containing culture material (FCCM), 15 crossbred wether lambs were dosed intraruminally with FCCM containing 0 (CONTROL, n = 3), 11.1 (LOW, n = 41, 22.2 (MED, n = 4), or 45.5 (HIGH, n = 4 ) mg of total fumonisins ( B 1, B2, and B3)/kg BW daily for 4 d. Blood samples were collected daily, and on d 11 lambs were lulled and necropsied. Changes in serum constituents in fumonisin-treated lambs indicative of liver damage, included increased ( P <

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... 05) activities of alkaline phosphatase, 7- glutamyl transferase, aspartate aminotransferase, and lactate dehydrogenase. Serum concentrations of cholesterol, triglycerides, urea nitrogen, and creatinine were also increased ( P < .05) in lambs dosed with FCCM. Hemoglobin tended to increase ( P = .07) and white blood cell count tended to decrease ( P = .08) in HIGH lambs and activated partial throm-boplastin time tended to decrease ( P < . l o ) i n lambs dosed with LOW and MED treatments. Mitogeninduced lymphocyte blastogenesis was not different ( P = .14) among treatments. Feed intake markedly decreased ( P < .O 1) following the first dosing of FCCM and continued to decline throughout the study. Ruminal VFA concentrations and pH tended to decrease ( P < . l o ) a t d 11 in treated lambs. Relative liver and kidney weights (g/lOO g of BW) increased ( P < .05) in fumonisin-treated lambs. Histological examination revealed tubular nephrosis and mild hepatopathy in dosed lambs. Lambs receiving the HIGH treatment died on d 3, 4, 5 , and 7 of the study and on d 9 one lamb on the MED treatment died. Diarrhea and lethargy were observed in fumonisintreated lambs. Fumonisin-containing culture material dosed orally is acutely toxic to sheep, affecting primarily liver and kidney function.