Measurement of Malabsorption of Carotenoids in Chickens with Pale-Bird Syndrome

Because pale-bird syndrome (PBS), defined as the failure of birds to realize the color potential of their diet, has been demonstrated to be caused by malabsorption or by hyperexcretion of carotenoids, a method for measuring malabsorption of carotenoids would be useful. The absorption of dietary canthaxanthin, a red diketocarotenoid, into serum during aflatoxicosis was measured in an experiment with a 2 × 9 factorial arrangement of treatments (0 and 5 μg of aflatoxin/g of diet; serum collected at 0, 2, 4, 6, 8, 10, 12, 14, and 24 h after a standard meal fed to four groups of 10 3-wk-old birds). Serum canthaxanthin levels determined by HPLC attained plateau values between 8 and 14 h after the meal. The absorption of canthaxanthin was depressed significantly (P<.05) in birds with aflatoxicosis from 4 to 24 h after feeding the standard meal. Four field flocks diagnosed as having PBS were tested for malabsorption by intubating 10 birds with a standard amount of canthaxanthin and measuring serum canthaxanthin 12 h later. One flock had about 85% normally pigmented birds and 15% extremely pale birds, the second flock had a coccidiosis history, the third had a Newcastle disease history, and the fourth had a history of both coccidiosis and Newcastle disease. The flocks were 5- to 6-wk-old, received feed of the same manufacture, and their disease outbreaks had occurred 2 wk earlier. The serum levels of canthaxanthin in the extremely pale birds of the first flock were significantly (P<.05) lower than in the normally pigmented birds, but significantly (P<.05) higher than the levels in the other flocks. A similar pattern occurred with serum lutein and zeaxanthin, which were normal dietary carotenoids. These observations imply that a standard meal or oral dose of canthaxanthin can be used to measure malabsorption in chickens and that maldeposition of absorbed carotenoids might be a new mechanism of action in PBS.