Seeds of the weed Datura ferox are frequent contaminants of raw materials used for animal feed. In this study a mixture of scopolamine and hyoscyamine (98:2), the 2 main alkaloids of Datura ferox seeds, was incorporated at 4 total alkaloid levels (1.5, 15, 75 or 150 mg/kg feed) into a control diet fed to 100 egg-laying hens for 3 mo. Alkaloid doses of 150 mg/kg feed reduced egg production for the first 5-6 w of feeding, whereas lower doses had no effect. Egg weight, eggshell thickness and body weight of hens were unaffected at all doses. Doses of 150 mg/kg feed produced significant increases in the cardiac rate of hens after 5 w. Breathing frequency at all doses was unaffected. Determination of plasma aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and leucine aminopeptidase activities, as well as autopsy and histological examinations, revealed no obvious alkaloid-related toxic effects. It was concluded that a total alkaloid dose as high as 75 mg/kg feed can be safely administered to egg-laying hens.