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Nutrients Affecting the Vitamin B₁₂ Requirement of Chicks¹

Laboratory of Nutrition and Endocrinology, National Institute of Arthritis and Metabolic Diseases, Public Health Service, U. S. Department of Health, Education and Welfare, Bethesda, Maryland

The effect of certain constituents of purified diets upon the vitamin B₁₂ requirement of chicks fed a high fat corn-soybean oil meal diet has been studied. It is concluded that:

1. The only nutrients having a significant vitamin B₁₂-sparing activity were methionine and choline. Methionine at a level of 0.15% completely replaced vitamin B₁₂, whereas addition of 0.2% choline chloride to the diet resulted in only a small sparing effect.

2. Free methionine was more effective in sparing vitamin B₁₂ than an equivalent amount of methionine present in casein (5% of the diet) or in an amino acid mix based on the amino acid composition of casein.

3. This same amino acid mix without methionine markedly suppressed growth of chicks below that of the group receiving no vitamin B₁₂. The addition of vitamin B₁₂ to the basal diet containing the methionine-free amino acid mix supported optimal growth. Thus, a greater response to vitamin B₁₂ was obtained under these conditions.

Manuscript received 15 February 1957.