A Study of Calcium and Phosphorus Balances with Dairy Cattle

The results of many years of study by numerous investigators and many practical aspects of the problem have developed an increasing interest in the utilization of calcium and phosphorus by dairy cattle.The limited ability of the dairy cow to utilize the mineral constituents of various rations was demonstrated in series of experiments by Forbes (1).Normal dry winter rations were fed and variously included, timothy, clover or alfalfa hay and in some cases corn silage.Negative calcium balances were obtained in all eases where the daily milk production exceeded 10 pounds, the losses being less with clover hay and alfalfa than with timothy hay.In most cases the phosphorus balances were negative.Hart and associates (2) reported an appreciable retention of calcium when alfalfa hay that had been cured under caps was fed to liberally milking cows.A more liberal storage resulted from the use of fresh green alfalfa.Positive phosphorus balances accompanied the storage of calcium.It was thought that the quality of the roughage determined the degree of calcium assimilation, by the term quality being meant the relative degree of destruction in the curing process of the unknown factors affecting calcium assimilation.Steenbock and associates (3) reported from results obtained with rats that alfalfa cured in the dark was very rich in vitamin A, even 0.5 per cent supporting normal growth when the anti-*