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.
