The possibility was examined of supplying vitamin A to chickens from the first days of life as carotene in green plants. Growth experiments were carried out with chickens till the age of 8 weeks. Different kinds of forage (horse-beans, Berseem clover, green oats, sweet potato leaves, cow-peas, corn-leaves) were given in quantities calculated to supply 300 μg. carotene per 100 g. feed; control groups received fish-liver oil, given at the level of 500 i.u. per 100 g. feed. Weight gains and extent of vitamin A storage in liver served as an indication of the utilization of carotene from different sources. The utilization of carotene from all the plants examined was sufficient to support normal growth, only in the groups receiving clover was growth found to be somewhat slower. Remarkable differences were found in the extent of liver storage, and that was taken as an indication of differences in activity of the carotene from the different sources.
Attempts to determine the reasons for these differences in liver storage capacity of the carotene from the various plants did not reveal the presence of any plant components enhancing or depressing vitamin A storage.
Similarly, no correlation could be found between digestibility coefficients of carotene in the different plants and liver vitamin A storage. This correlation seemed likely in sweet potato leaves only, the rather low digestibility coefficient found in these leaves may account, at least partially, for the low activity of this plant.
The stereoisomeric composition of the β-carotene of the different plants and the xanthophyll/carotene ratio are very similar in all plants tested and cannot account for differences in carotene activity of the plants studied.
The results of this work show that it is possible to satisfy the requirements of chicks for vitamin A from the first days of life by supplying certain forage plants. In practice, because of the variability of the carotene content in such plants, care has to be taken when estimating the amounts to be given. Green plants should be given to chickens freely or at least in liberal amounts.