A Study of the Phosphorus Requirement of Dairy Cattle: II. Phosphorus, Calcium and Nitrogen Metabolism of Dairy Cattle When Alfalfa Furnishes the Principal Source of Protein

Abstract

Summary 1.A study was made of the phosphorus, calcium and nitrogen metabolism of heifers before calving and when in milk, on a basal ration low in phosphorus and on the basal ration supplemented with special steamed bone meal, in which alfalfa hay furnished the principal source of protein. 2.Positive phosphorus, calcium and nitrogen balances were obtained in the heifers of both lots before calving. Apparently 10.81 to 12.25 grams of phosphorus per day furnished a sufficient amount of this element for growth and pregnancy from 18 to 30 months of age. 3.Phosphorus balances during heavy milk production were usually negative on a ration of low phosphorus alfalfa hay, corn silage and corn, with or without blood meal. The phosphorus balances were positive, however, on the same ration supplemented with bone meal. 4.The cows on a low phosphorus ration utilized food phosphorus more efficiently than those on a high phosphorus ration. 5.Lack of appetite for roughage often prevented metabolism studies of the animals on the low phosphorus ration.