Meat Diets

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Abstract
Middle-aged piebald female rats, reared with a stock diet, were transferred to a diet of raw minced beef, deficient in calcium. They survived for long periods, sometimes over a year, without developing gross skeletal abnormalities, and with little or no demineralization. In contrast, weanling rats, fed the same meat, stopped growing after a few weeks, developed severe skeletal lesions and demineralization and usually died. The provision of calcium supplements to weanlings for graded periods, before restriction to meat without calcium, increased their ability to grow and thrive on the meat. With only 3 weeks of supplementation, for example, the rats all grew normally during an experiment lasting 4 months. Such rats appeared to be in perfect health, and had normally shaped bones. To a marked degree, however, the urge for growth had taken precedence over the demand for normal mineralization of the bones. Thus the ash content of their femurs was only one-half that of rats that had received calcium continuously. Severe stunting of growth, and fractures, occurred only when the ash content of the bones was one-third, or less, of the normal level. These observations emphasize the crucial influence of age, in rats previously adequately supplied with calcium, on their resistance to subsequent dietary deficiency of calcium. On a body weight basis the calcium demands of weanlings must be at least 20 times those of adults. Hypochromotrichia, due to an absolute or conditioned deficiency of copper, was observed in the middle-aged rats fed raw steak. It was cured by impure iron carbonate, containing copper. Calcium was also effective against hypochromotrichia, in these middle-aged rats, in a way not yet understood. In all the weanlings hypochromotrichia was prevented by supplements of copper.