Studies in mineral metabolism XXXVII. The influence of variations in the dietary phosphorus and in the Ca:P ratio on the production of rickets in cattle

Abstract

1. Young heifers and steers were fed basal rations supplemented with CaCO₃ and Na₂HPO₄ in such a manner that the intakes of Ca and P were different in the respective groups. Vitamin D was present in abundance. 2. The basis of the experiments was respectively deficiency and sufficiency of P with varying amounts of Ca in the rations. 3. The experiments continued for approximately 24 months. during which period observations were recorded on weight increase, food consumption, blood analysis for P, Ca and phosphatase, clinical symptoms of disease and bone analyses – both chemical and histological. 4. The outstanding result of the experiments is that under the conditions mentioned P deficiency in bovines invariably leads to rickets or osteomalacia and that osteodystrophia fibrosa is not produced by P deficiency per se. With regard to the latter condition the suggestion is made that Ca deficiency may be the responsible factor. 5. Erdalkali-alkalizitat, like Ca:P ratio of which it really is a modification, is not the factor which determines whether rickets will or will not develop under conditions of P deficiency but both are associated with the severity of the complex result produced; for instance if they are not always associated with the severity of the microscopical bone lesions then with the earlier effects upon food consumption, growth and the development of clinical symptoms. 6. From the data available it would appear that a ratio of CaO:P₂O₅ of 2.5:1, when P was present in adequate amounts did not affect the animals significantly in regard to the observations registered. 7. A daily intake of 19 gm. P₂O₅ of which 53 per cent. was retained by the steers and of 24.0 gm. P₂O₅ with a retention of approximately 63 per cent. by the heifers provided sufficient P for normal growth and development while 13 gm. and 10 gm. were insufficient for the steers and heifers respectively. 8. Decreased food consumption which has invariably been observed in cattle receiving insufficient amounts of P in their diets is not wholly due to the inadequacy of the P but is also associated with the calcium content of such a diet or apparently therefore an effect of a disturbance in the Ca:P metabolism of the animal. 9. With regard to blood analysis the phosphatase and the inorganic P content of the blood afford valuable assistance in following the development of rickets but Ca determinations have been found to be of little help in presence of vitamin D. The periodic removal of portions of ribs causes the animal very little inconvenience and has advantages even over X-ray photography for studying the development of osteodystrophic diseases in the experimental animals.