Folate deficiency in rats fed diets containing free amino acids or intact proteins.

Development of folate deficiency (FD) was evaluated in weanling rats fed diets containing mixtures of free amino acids or of vitamin-free casein and gelatin as sources of dietary nitrogen. FD could be produced in 21 d with amino acid diets that promoted maximum growth rate, were completely devoid of folate and contained 1% succinylsulfathiazole. Growth retardation and blood dyscrasia associated with FD could not be demonstrated in rats fed diets containing casein and gelatin as nitrogen sources because the vitamin-free casein contained low but measurable levels of folate. The most effective protocol to produce experimental FD in rats is to feed a folate-free diet that otherwise supports maximum growth in young animals. Additional modifications such as use of methotrexate or amino acid-imbalanced or protein-deficient diets are unnecessary.