CALCIUM AND PHOSPHORUS IN THE FEED OF DAIRY COWS. 15 



mimal served as a control one year and as an experiment animal the 

 lext year. In a typical experiment an animal would receive daily 

 'or 60 days before calving 3 pounds of grain mixture C, 4 pounds 

 ilfalfa hay, and 30 pounds corn silage. The, next year she would 

 "eceive in the corresponding period the same average daily quantities 

 >f the same feed, but instead of receiving equal amounts of all the 

 ! eeds every day, she would receive on one day no grain, 8 pounds of 

 df alf a hay, and 30 pounds corn silage, and the next day 6 pounds of 

 ^rain with sodium phosphate added to it, no hay, and 30 pounds of 

 :orn silage. For the sake of brevity the first procedure will be 

 poken of as the " control feeding," the second as the " experimental 

 eeding " or the " alternated feeding with phosphate." 



The animals which received the phosphate were fed alternated 

 •ations, as above described, with the idea of separating to some extent 

 he calcium and phosphorus compounds in the intestinal tract. There 

 s a good deal of evidence to show that the absorption of phosphorus 

 ! rom the intestinal tract may be hindered by the simultaneous pres- 

 nce of calcium compounds (1), (4), (7). As the hay contains most 

 f the calcium of the rations, and the grain most of the phosphorus, 

 he experimental animals received an excess of calcium one day and 

 n excess of phosphorus the next. When the average daily ration was 



pounds of grain mixture CP, 4 pounds alfalfa hay, and 30 pounds 

 orn silage, they received about 61 grams of calcium and IT grams of 

 >hosphorus on the days when they were fed hay ; and about 16 grams 

 f calcium and 50 grams of phosphorus on the grain days. 



After calving, the controls and experiment animals were fed alike 

 >r according to their milk yields. As the milk yield for the first five 

 »r six weeks after calving is not much influenced by small changes in 

 he contemporaneous food supply (2), we have not thought it neces- 

 ;ary to give a detailed account of how the cows were fed during this 

 )eriod. 



The milk and fat yields of the control and experiment animals were 

 'ollowed 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 

 s a measure of the effect of the alternated feeding with phosphate. 

 ji many cases the body weights of the animals were also followed 

 luring the periods when they were on the control or the experimental 

 eeding. 



It was decided to use sodium phosphate as the mineral supplement, 

 tartly in order to study the effects of phosphorus as distinguished 

 ! rom calcium, partly because the phosphates of sodium are much 

 nore soluble in neutral solutions than any of the phosphates of 

 :alcium, and it was judged that feeding the more soluble salts would 

 produce the maximum effect of the phosphorus on metabolism. Di- 



