Self-selection of ascorbic acid in coloured foods by heat-stressed broiler chicks

Female broiler chicks were given red and green supplemented (200 mg ascorbic acid (AA)/kg) and unsupplemented foods on alternate days for 8 days under heat-stressed and unstressed conditions. After this training period, the birds were given access to both foods, and the intake of each was monitored. In both heated treatments the intake of the supplemented food was significantly higher (p < 0.05) than of the unsupplemented food (800 vs. 518 g/14 days), although in the unheated groups significantly more of the unsupplemented food was eaten (756 vs. 639 g/14 days). Birds were unable to select for AA when neither food was coloured, even when they were presented continuously in the same positions in the cage. It is concluded that chicks can learn to associate the colour of the food with its AA content and that they select proportions of supplemented and unsupplemented foods appropriate for their needs, as influenced by environmental temperature.