CALCIUM AND PHOSPHORUS IN THE FEED OF DAIRY COWS. \) 
DISCUSSION OF RESULTS. 
Our, results indicate that the milk yield of the general herd at 
Beltsville has been reduced by an insufficiency either of calcium or 
of phosphorus, or of both, in the rations, in spite of the facts that 
these contained more than the average proportions of both calcium 
and phosphorus and were fed in the amounts required according to 
the feeding standards. We think it is still an open question whether 
calcium or phosphorus has been the element chiefly lacking, and 
whether the rations could be improved from the standpoint of min- 
eral nutrition by varying the proportions of the different feeds used. 
Work aimed to throw light on these problems is now being carried 
out here. In the meantime, however, it seems worth while to con- 
sider what the knowledge already at hand indicates ought to be 
done. 
Table 1 contains the cases where a cow s record after the phosphate 
feeding is compared with a previous record of her own made after a 
period on the basal ration. It will be noted that in most of these 
cases the basal ration was fed before the first calf was born. The 
results as given in this particular table, therefore, are chiefly evi- 
dence for the view that the heifers received insufficient calcium or 
phosphorus in the rations supplied to them before they had their 
first calves. 
We believe that this was the case, and we shall later discuss the 
rations supplied to the heifers which had never had calves. But the 
records for the general herd indicate that, under the Beltsville 
routine, the animals never recovered from the mineral shortage which 
made itself evident in the first lactation period. 
The evidence from the records which indicates this may be summed 
up as follows : In the case of the animals born at Beltsville and kept 
under the routine treatment there was no tendency for the milk yield 
to rise after the first lactation period to the extent that it did in the 
cases of cows 54, 63, 71, and 81, shown in Table 1. The rise as be- 
tween the first and subsequent lactation periods was approximately 
that which would be expected from the data collected by Pearl and 
Patterson (14) and by the Holstein and Guernsey breeding asso- 
ciations. In the case of animals brought to the farm from other 
places and kept under the routine treatment, there was frequently a 
tendency for the milk yield to fall off more rapidly than it should 
with advancing age, as in the cases of cows 17 and 201, figures 1 and 2. 
As many of the cows which received the alternated rations with 
phosphate received a basal ration somewhat lower than that fed to 
the general herd during their dry periods, it is fair to compare the 
milk yields of these two sets of animals. Cows 49, 54, 71, and 81 may 
be taken as representing the effects of the phosphate feeding in the 
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