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Cod liver oil is the richest natural source of two vitamins which play an important part in the diet of both human beings and animals, vitamins A and D. That the former is readily destroyed by oxidation, through exposure to air, is generally accepted, but in spite of evidence to the contrary it is still believed by many people, particularly by those dealing with the utilization of cod liver oil, that vitamin D cannot be destroyed by exposure to air or that it is so extremely resistant to such oxidation that the question of destruction by exposure to air need be given no consideration.It seems probable that this conception of the stability of vitamin D has arisen from the fact that this vitamin was distinguished from vitamin A through a difference in the relative rate of oxidation when heated and exposed to air. As early as 1921, Mellanby1

A microbiological assay for vitamin B12using Lactobacillus leichmannii(ATCC 4797) has been developed. The assay medium contains crystalline amino acids as the nitrogen source and adsorbed tomato juice filtrate as a source of unidentified growth factors. A high level of cysteine and ferrous sulfate are present in the medium to keep it in the necessary reduced state. Data are given to show the degree of precision and reproducibility to be expected from the assay.

Chicks which are rendered micromelic during embryonic development as a result of manganese deficiency do not recover from this condition when fed a diet adequate in manganese during a period of time greatly in excess of that required for the attainment of maturity.

The relative effectiveness of ingested and injected manganese in preventing the development of perosis in chicks fed a high calcium-phosphorus diet was studied. The results obtained showed that excess calcium and phosphorus in the diet greatly reduces the availability of manganese in the intestinal tract.

It is evident from these results and also from the known character of the ration fed that a factor is required for growth and reproduction in the domestic fowl other than vitamins A, B, B4, B6, D, E, K, riboflavin, the chick antidermatosis vitamin, nicotinic acid, factor W, the antiencephalomalacia factor and the essential fatty acids. It appears improbable that this factor is the grass juice factor,6since corn and wheat are reported to be poor sources of the latter factor. It also is improbable that the factor is protein in nature. The factor is destroyed by heating in a dry atmosphere for 36 hours at 120°C. It is present in cereals, yeast and milk.

Betaine and methionine have been shown to be effective in preventing perosis and promoting growth in chicks when added to a simplified diet. They were ineffective when added to a purified diet of higher methionine content. In contrast, choline prevented perosis and promoted growth on both diets.The results indicate that choline is required as such for the prevention of perosis and for growth and that betaine and methionine when added to the simplified diet enabled the chick to synthesize choline. This may be caused by an unidentified factor present in the simplified diet which is necessary for choline synthesis. Another possible explanation is that a factor which inhibits choline synthesis is present in the purified diet.When the casein in the purified diet was replaced with an isolated fraction of the proteins of soybeans with resultant reduction in methionine content, betaine and methionine failed to prevent perosis but promoted some growth. The growth response obtained with betaine and methionine in this instance is believed to be due to a deficiency of methyl groups only. Choline was again effective for both purposes.

The folic acid requirement of chicks for growth, feathering, and hemoglobin formation has been determined using a purified diet containing 2.0 μg of preformed folic acid per 100 g of diet. The total folic acid content of the basal diets as determined microbiologically following incubation with chick liver was 5 μg per 100 g of diet for Experiment 1 and 15 μg for Experiments 2 and 3.The following amounts of folic acid, which include the amount in the basal diet, were required for its several functions: for survival to 6 weeks of age, approximately 25 μg per 100 g; for growth and hemoglobin formation at 4 weeks of age, 45 μg; for growth at 6 weeks, 45 μg, but for hemoglobin formation at 6 weeks, 35 μg; and for feathering at 6 weeks of age, not less than 55 μg per 100 g of diet.In these experiments the addition of succinylsulfathiazole at 1 or 2% of the diet did not have any effect on growth, feathering, or hemoglobin formation in chicks to 6 weeks of age.

In severe experimental hemorrhagic anemia in hens, the injection of β-pyracin and Lactobacillus caseifactor, alone and in combination, was found to hasten the regeneration of hemoglobin. When these factors were administered together, however, the rise in hemoglobin was much more rapid and the level reached was higher than in the lots administered the factors alone.The hemoglobin levels in the control lots rose above the "pre-bleeding" values and then began an almost immediate decline to approximately the original level. In the lots receiving β-pyracin and Lactobacillus caseifactor, alone or in combination, the hemoglobin levels also rose above the "pre-bleeding" values but were maintained for some time after injections were discontinued before declining to the original values.

Microbiological data have been presented on the distribution of vit. B12in the tissues and organs of chicks fed a purified diet containing a high level of vit. B12. Kidney was found to contain the most vit. B12while liver and pancreas contain lesser quantities. Muscle, except for the heart, is low in vit. B12under these conditions. A comparison of these results with other published data indicates that certain organs, particularly the kidney, liver and pancreas, have the ability to store appreciable quantities of vit. B12.