Published online by Cambridge University Press: 27 March 2009
The results of carotene metabolism experiments with four cows and four bullocks have been discussed. It has been shown that under ordinary farm diet, cows may secrete milk with a fair amount of carotene and vitamin A potency and still themselves remain on negative carotene balance, so far as the current intake and outgo are concerned. Increased intakes of carotene are, however, followed by the increased carotene and vitamin A potency of milk. Experiments with bullocks on a carotene-low diet consisting of dry rations have shown that the faecal carotene elimination attains a constant value and the animals show a consistently negative carotene balance. When, however, two doses of berseem are superimposed on this basal ration, positive retentions of carotene are obtained, followed by a rise in the blood-carotene level. The experimental evidence points to the possibility of a part of the faecal excretion being the result of a withdrawal of carotene from the body reserves.