The effects of continuous feeding of graded levels (.5, 1.0, 2.0 ppm) of ochratoxin A (OA) for eight weeks to male and female broiler chickens were investigated. A depression in body weight gain was observed in all groups receiving OA. The depression was proportional to the level of exposure to OA and was more marked and prolonged in males than in females. Detectable residues of OA were observed in the liver and kidney of birds fed 2 ppm OA. Residues disappeared from liver within 24 hr and from kidney within 48 hr after withdrawal of the mycotoxin from feed. No residues of OA were found in muscle or fat.

The comparative acute, oral toxicity of ochratoxin A for three day-old avian species is presented. The seven-day LD50 value for White Leghorns was calculated to be 3.4 +/-0.19 mgm./kg., for turkeys to be 5.9 +/- 0.72 mgm./kg., and for Japanese quail to be 16.5 +/- 0.56 mgm./kg., body weight. The dose-response curves are linear and parallel through one standard deviation on either side of the LD50 when log-dose is plotted against probit for survivors. It is suggested that the mechanism of action of ochratoxin A is similar in the three species, though the potency differs. The reduction in weight gain of Leghorn survivors was proportional to dose, and was observed in two separate traials over an overall dosage range from 0.2 mgm./kg. to 5 mgm./kg. The turkeys showed only a slight reduction in weight gain at doses less than 4mgm./kg., a more marked reduction being observed at higher dose levels. The quail did not show reduction of weight gain at dose levels below 10.9 mgm./kg., though the reduction was proportional to dose at higher levels. All birds dying of acute ochratoxicosis revealed a progression of symptoms from listlessness, huddling, occassionally diarrhoea, ataxia, prostration and death. Viscereal gout was observed at necropsy of the Leghorns.

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