Evaluation of the preruminant calf as a model for the study of human carotenoid metabolism.

This study evaluated the preruminant calf as an animal model for the study of human carotenoid metabolism. Fifteen newborn male Holstein calves were fed a carotenoid-free milk replacer diet to maintain them in the preruminant state. After a 7-d adjustment period, three calves were killed and 12 calves received a single oral dose (20 mg) of beta-carotene in the form of water-soluble beadlets. Blood samples were collected periodically and samples of various tissues were collected when the calves were killed. Three animals each were killed by exsanguination at 1, 3, 6 and 11 d post-dosing. Serum beta-carotene concentrations peaked between 12 and 30 h post-dosing and declined slowly afterwards. Serum data were fitted to a two-compartment model and yielded an elimination constant (k2) that was similar to reported human values. Adrenal tissue showed significant concentrations of beta-carotene by 24 h post-dosing, and levels were still elevated at 264 h. Liver, spleen and lung beta-carotene concentrations were significantly elevated by 24 h and rapidly declined thereafter. Adipose and kidney peak beta-carotene concentrations were observed at 72 and 144 h, respectively. Heart and muscle did not display significant changes in beta-carotene concentrations. The preruminant calf shows promise as an animal model for the study of absorption and metabolism of carotenoids by humans.