CALCIUM AND PHOSPHORUS IN THE FEED OE DAIRY COWS. 15 
animal served as a control one year and as an experiment animal the 
next year. In a typical experiment an animal would receive daily 
for 60 days before calving 3 pounds of grain mixture C, 4 pounds 
alfalfa hay, and 30 pounds corn silage. The next year she would 
receive in the corresponding period the same average daily quantities 
of the same feed, but instead of receiving equal amounts of all the 
feeds every day, she would receive on one day no grain, 8 pounds of 
alfalfa hay, and 30 pounds corn silage, and the next day 6 pounds of 
grain with sodium phosphate added to it, no hay, and 30 pounds of 
corn silage. For the sake of brevity the first procedure will be 
spoken of as the " control feeding," the second as the " experimental 
feeding " or the " alternated feeding with phosphate." 
The animals which received the phosphate were fed alternated 
rations, as above described, with the idea of separating to some extent 
the calcium and phosphorus compounds in the intestinal tract. There 
is a good deal of evidence to show that the absorption of phosphorus 
from the intestinal tract may be hindered by the simultaneous pres- 
ence of calcium compounds (1), (4), (7). As the hay contains most 
of the calcium of the rations, and the grain most of the phosphorus, 
the experimental animals received an excess of calcium one day and 
an excess of phosphorus the next. When the average daily ration was 
3 pounds of grain mixture CP, 4 pounds alfalfa ha}^, and 30 pounds 
corn silage, they received about 61 grams of calcium and IT grams of 
phosphorus on the days when they were fed hay ; and about 16 grams 
of calcium and 50 grams of phosphorus on the grain days. 
After calving, the controls and experiment animals were fed alike 
or according to their milk yields. As the milk yield for the first five 
or six weeks after calving is not much influenced by small changes in 
the contemporaneous food supply (2) , we have not thought it neces- 
sary to give a detailed account of how the cows were fed during this 
period. 
The milk and fat yields of the control and experiment animals were 
followed for the first 40 days after calving, and, as a rule, the milk 
produced from the tenth to the fortieth day after calving was taken 
as a measure of the effect of the alternated feeding with phosphate. 
In many cases the body weights of the animals were also followed 
during the periods when they were on the control or the experimental 
feeding. 
It was decided to use sodium phosphate as the mineral supplement, 
partly in order to study the effects of phosphorus as distinguished 
from calcium, partly because the phosphates of sodium are much 
more soluble in neutral solutions than any of the phosphates of 
calcium, and it was judged that feeding the more soluble salts would 
produce the maximum effect of the phosphorus on metabolism. Di- 
