Survival of germfree rats without vitamin A.

Weanling, germfree rats, transferred to a conventional animal room and fed a vitamin A-deficient diet, died in 23 to 54 days. In contrast, their littermates, kept germfree and on the same diet, survived for as long as 272 days. The rats kept in germfree conditions stopped growing after 1 to 4 months but responded to supplements of retinoic acid.