Elmer De Ritter

Vitamin a Requirements of Animal Species

Publisher Summary In considering the requirement of an animal for a vitamin, a prime question concerns the criteria to be used. In general, the minimum requirement of a species for vitamin A has been considered to be that level, which gives satisfactory growth and prevents lesions or dysfunctions because of vitamin A deficiency. This is, perhaps, a somewhat arbitrary standard, which does not consider other important factors influenced by vitamin A intake: tooth development, longevity, and maintenance of adequate liver stores and blood levels of vitamin A, particularly during pregnancy and lactation. The amount of vitamin A required to provide optimal conditions with regard to these latter considerations may be widely different from the minimum requirement established on the usual basis noted above. In other words, the daily intake needed to correct or prevent a frank clinical deficiency may be quite different from the amount necessary to correct or prevent a deficiency the existence of which can be elicited only by examination with special means or by special analyses.