Abstract
In our experimental work we have made observations which demonstrate in a striking way the differences in the effectiveness of cod liver oil as contrasted with butter fat in influencing the rate and extent of growth, and their effects on the histological structure of the bones. This is well illustrated by the results of restricting young rats to the following diet:
This diet induces fairly good growth and fertility during at least 8 to 10 months, notwithstanding its deficiency in calcium. The calcium content of this food mixture is 0.059 gms. per 100. The optimum calcium content of this diet is reached when about 1.5 per cent. of calcium carbonate is added. The phosphorus content of this mixture is 0.3546 gms. per 100, and is not far from the optimum content. This food mixture is slightly alkaline owing to its content of sodium bicarbonate.
This food mixture with butter fat to the extent of 3, 10, or 20 per cent. of the food mixture fails to induce an appreciable amount of growth. With 2 0 per cent. of butter fat the animals gain but a few grams in weight, look very inferior, become short and stocky, and are rough coated.
This diet when 10 per cent. of casein is added, but without the addition of either butter fat or cod liver oil, causes pathological changes characteristic of rickep. With small amounts of cod liver oil (3 per cent.) no rachitic changes are seen in the bones. Even 20 per cent. of butter fat fails to effectively direct the growth processes in the bones toward the normal condition. They usually die within a few months.
This food mixture containing 3 per cent. of butter fat and 1.5 per cent. of calcium carbonate is a highly satisfactory diet for the promotion of growth to the full adult size, the maintenance of high fertility throughout the breeding period in the females and the successful nutrition of the young by the mother's. Even a fifth
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