Avian gout caused by oosporein, a mycotoxin produced by Caetomium trilaterale

In a series of four experiments, diets containing oosporein at graded concentrations from 0 to 600 microgram/g were fed to male broiler chicks from hatching to 3 weeks of age. At dietary toxin levels of 100 microgram/g and below, no detrimental effects were observed. Dietary oosporein concentrations of 200 microgram/g and above elicited dose-related mortality resulting from severe visceral and articular gout. Three-week cumulative mortality percentages were 0, 13, 30, 57, and 95% for the 0, 200, 300, 400, and 600 microgram/g levels, respectively. Upon necropsy, the prominent lesions observed were massive urate deposits in various tissues, swollen and pale kidneys, dehydration, proventricular enlargement with mucosal necrosis, and a green discoloration of the gizzard lining. The effects on the proventriculus and gizzard occurred at doses as low as 200 microgram/g and were the most sensitive indicators of oosporein-toxicosis. In addition to the proventriculus, the relative weights of the kidney and liver were significantly increased in a dose-related fashion. A significant reduction in 3-week body weight at 400 microgram/g apparently resulted from the lower feed consumption concomitantly observed at this level of dietary toxin. Oosporein also caused an increase in water consumption at 400 and 600 microgram/g. Blood analyses indicated no toxin-related effect on plasma glucose, plasma protein, packed red blood cell volume, hemoglobin, and prothrombin times. The plasma concentration of uric acid was significantly elevated at 400 microgram/g. These data and mechanistic considerations suggest that oosporein should be classified as a nephrotoxin in the broiler chicken.