CALCIUM AND PHOSPHORUS IN THE FEED OF DAIRY COWS. 7 



mals should have plenty of calcium in their rations, and therefore all 

 received alfalfa hay in quantities which it was hoped would provide 

 sufficient calcium. 



The details of the experimental procedure and the results obtained 

 are given in the description and tables at the end of the article. 



The experiments consisted essentially (a) in drying cows off about 

 60 days before they were due to calve, (b) in feeding the controls a 

 certain basal ration, (c) in feeding the others the same basal ration, 

 giving grain and hay on alternate days and adding sodium phos- 

 phate to the grain, and (d) in following the milk yields from the 

 tenth to the fortieth day after calving. 



Some of the animals used in the experiments were from the general 

 herd, and had previously been fed approximately according to the 

 Savage feeding standard. Others had been on test during the year 

 preceding the experiments, and had been fed much more liberally. 

 In the case of the animals from the general herd (see Tables 1 and 2) 

 the alternated feeding with phosphate had a very favorable influence 

 on the subsequent milk yield ; but in the case of those which had been 

 on test (Table 3), the effect was insignificant. This indicates that 

 the rations fed to the general herd were deficient in one or both of the 

 principal bone-building elements. 



The results show that the effect of the alternated feeding with 

 phosphate on the subsequent milk yield will depend on the previous 

 history of the cows as well as on the amount of phosphorus contained 

 in the basal ration. It follows that the quantitative results of the 

 experiments are significant only for the special conditions under 

 which they were carried out. They might be entirely different in a 

 herd whose previous history had been different, or with a basal ration 

 which contained a different amount of phosphorus. 



The attempt has been made, however, to get an approximately 

 quantitative idea of the increase in milk yield produced by the phos- 

 phate feeding under the conditions of experimentation used with the 

 cows of the general herd. For this purpose, only those animals have 

 been considered which figure both as controls and as experiment ani- 

 mals and whose histories are given in Table 1. The method and 

 results used in this attempt are given in Table 8 with its appended 

 comment and in figure 3. The animals gave, on the average, 37.9 per 

 cent more milk after the phosphate feeding than would have been 

 expected from their previous performance. 



The milk yield from the tenth to the fortieth day after calving 

 has been taken as the most important measure of the effect produced 

 by the alternated feeding with phosphate during the preceding dry 

 period. But certain other aspects of the effect produced by this 

 treatment have also been studied. 



