RELATION OF VITAMIN-D TO CALCIUM AND PHOSPHORUS RETENTION IN CATTLE 195

The average normal daily retention of 6.42 grms. of calcium and 3.22 grms.
of phosphorus obtained in this work is almost exactly in a two to one ratio irres-
pective of the varying amounts in the ration fed. This closely approximates the
ratio of these two elements in the bodies of growing and mature cattle. Lindsey,
Archibald, and Nelson (7) noted the same relationship in their work with normal
animals. It is of interest to note that in this work the slight average daily posi-
tive balances of 0.51 grms. of calcium and 0.24 grms. of phosphorus shown by
the rachitic calves are also in an approximately two to one ratio. Also, that the
loss of calcium and phosphorus in the case of E-185 showed this ratio. Such
observations indicate an ultimate interdependence between the two elements
and suggest that a deficiency in one might be responsible for a lack of retention
of the other.

The fact that the calves receiving prairie hay as roughage continued through-
out the experiment in an apparently normal condition irrespective of whether or
not they received any vitamin -D supplement, whereas those on a similar or
even higher mineral intake but receiving beet pulp soon showed symptoms of a
vitamin-D deficiency, indicates that the prairie hay undoubtedly carried an ade-
quate amount of the antirachitic factor, while the beet pulp contributed very
little, if any. The vitamin-D assays with laboratory animals furnished corro-
borative and conclusive evidence on the above points. When the two lots of prairie
hay were fed to rachitic rats definite healing was obtained, although it was more
pronounced for one lot than for the other. No signs of healing were evidenced
when the beet pulp was fed.

The assays furnish a basis for estimating the amount of vitamin D supplied
the calves by the hay contained in their rations. Rough calculations indicate
that the average hay allowance supplied the calves with approximately 135 Steen-
bock units of vitamin-D daily, which served to protect the calves from developing
the rachitic-like syndrome on the level of mineral intake furnished by these rations.
Just how much less may have sufficed to protect the animals cannot be deter-
mined from these observations. These estimation indicate that the vitamin-D
requirement of this species is relatively small as compared with the requirement
of infants as recently reported by Hess and Lewis (8), while the fact that an in-
creased mineral intake and changes in the calcium/phosphorus ratio failed to
protect the calves or initiate appreciable healing suggests the possibility that
calves are less independent of vitamin-D than the rat.

Some suggestions as to the amount and length of storage of vitamin-D by
calves are also indicated by the results obtained. The viosterol fed to the calves
as a therapeutic agent supplied roughly 15,000 Steenbock units daily, which is
over 100 times the amount furnished by the hay. The exact amount which would
have proved sufficient is not known but if the vitamin-D in the viosterol had
been used efficiently and the excess stored, the animals should have accumulated