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Cornell University, Ithaca, New York
Abstract
Forty Holstein male calves were used in two experiments to determine the phosphorus requirement. At 12 weeks of age the calves were changed from a grain-hay pre-experimental ration to a semi-purified basal ration containing 0.09–0.10% phosphorus. Dicalcium phosphate was added to the basal ration to supply total phosphorus levels on an air-dried basis of 0.09, 0.12, 0.18 and 0.30% in Experiment I. In Experiment II the dietary phosphorus levels were 0.14, 0.22, 0.30 and 0.38%. Twelve different response criteria were utilized and among them were feed intake and efficiency, body weight gains, serum inorganic phosphorus and alkaline phosphatase activity, bone ash, and bone growth as measured from femur and rib autoradiographs.
Autoradiographs proved to be a sensitive, precise and accurate technique for measuring the growth of the long bones. It appears that this method might be used to determine the adequacy of other nutrients which affect bone growth.
From these studies it is evident that the minimum phosphorus requirement of calves weighing from 200 to 275 lb. at 12–18 weeks of age approximates 0.22% of the air-dried ration. This means that feeding standards recommending as high as 0.40% phosphorus for calves of this size may be safely scaled downward. Adding a factor of safety to the minimum requirement, it is recommended that 0.30% phosphorus be included in the ration of calves of the size and weight employed in these studies.
1 Present address: Animal Industry Department, North Carolina State College, Raleigh, North Carolina.
2 The authors express their appreciation to the Grange League Federation for financial support of the research reported herein.
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