CALCIUM AND PHOSPHORUS IjNT THE FEED OF DAIRY COWS. 13 

 DESCRIPTION OF EXPERIMENTS, PROTOCOLS, AND TABLES. 



EFFECTS, ON MILK YIELD, OF LIBERAL FEEDING DURING DRY PERIOD. 



Cow 17, a grade Jersey, was born in 1909 and brought to the Belts- 

 ville farm in 1912. The protein and total nutriment contained in 

 her rations during the years 1914, 1915, 1916, and 1917 were calcu- 

 lated and compared with the quantities required for her maintenance 

 and for her milk and fat yield according to the Savage standard 

 (9), and it was found that she received on the average a surplus 

 of about 10 per cent of protein and about 2 per cent total nutriment. 

 It may be considered, therefore, that she was fed as nearly accord- 

 ing to this standard as is possible under any ordinary conditions. 

 She was on pasture for only 7 days during the four years under con- 

 sideration. She had a calf toward the end of the summer of each 

 year; the 1917 calf was born six weeks ahead of time, but it sur- 

 vived and was alive and well in June, 1920. The other three calves 

 were all born at term. Her dry periods were 44 days on the average. 



In 1914 she gave 5,709 pounds of milk; in 1915, 5,121 pounds; in 

 1916, 5,056 pounds; in 1917, 4,693 pounds; and in 1918, 2,569 pounds. 6 

 In 1918 she was given a dry period of 122 days, with approximately 

 the same ration as in previous dry periods. She calved December 11, 



1918, and her milk yield for 1919 rose to 5,578 pounds. 



During her dry periods in 1914, 1915, and 1917, she was fed 4 

 pounds of grain mixture B, 4 pounds of legume hay, and 30 to 35 

 pounds of corn silage. During her dry period in 1916 she received 

 4 pounds of grain mixture B, 3 pounds of oat hay, 28 pounds of corn 

 silage, and had 7 days on pasture. During the last 53 days of her 

 1918 dry period she was fed 4 pounds of grain mixture C, 4 pounds 

 of legume hay, and 30 pounds of corn silage. Her milk yields for 

 the first clear month after calving in each of the five years under 

 consideration were as follows: October, 1914, 799 pounds; Septem- 

 ber, 1915, 731 pounds ; September, 1916, 690 pounds ; November, 1917, 

 416 pounds ; and January, 1919, 873 pounds. 



The milk yield for the first six weeks after calving is not markedly 

 influenced by moderate changes in the feed supplied (2), and the 

 rations given in the months mentioned above were so nearly equiva- 

 lent that they could not have produced the observed differences in the 

 milk yield. These are to be attributed, therefore, to the nutritive 

 condition of the cow in her dry periods. The large yield for January, 



1919, is the result of the long dry period with a ration considerably 

 above the maintenance requirement. 



Cow 201, a purebred Holstein, was born March 13, 1905, and 

 brought to Beltsville in 1912. The protein and total nutriment con- 



6 This very low yield is partly explained by the facts that the cow aborted in 1917 and 

 that she had an unusually long dry period in 1918. 



