280 ILLINOIS STATE DAIRYMEN'S ASSOCIATION. 



lime or cement; she may and does change the form of the nu- 

 trients of the feed, but she cannot put into her milk what she 

 does not receive in her feed. She will build just so far as the 

 material supplied her will permit, or up to the limit of her ca- 

 pacity. 



If a cow were fed carbohydrates only, she would die in a 

 short time; if she were fed fat only, she would die in a short 

 time; if she were fed protein only, she would finally die. In 

 each case she could make no milk without drawing on her body 

 materials for some portion of it. If the mason is short of 

 cement, he can use more sand and build with a poorer mortar, 

 but not so with the cow ; she keeps the proportions in the milk 

 practically the same, and when one material is lacking, the milk 

 flow is limited by it regardless of how much of the other ma- 

 terials is present. Hence this experiment to show the extent 

 of the losses involved in feeding unbalanced rations. 



Plan of the Experiment. 



This test started January I, and continued until May n, 

 13 1 days. 



Twenty cows were divided into two lots of ten each. The 

 two lots were as nearly equal in production and other character- 

 istics as they could be divided, taking into consideration both 

 their production at the time of the division and their previous 

 records. Later it became necessary to remove one cow from 

 Lot 1 and in order to keep the lots even a cow was removed from 

 Lot 2 also. 



After the two cows were removed, the average milk pro- 

 duced daily by Lot 1 during the preliminary week was 37.8 

 pounds per cow, and that by Lot 2, 36.18 pounds. This differ- 

 ence in production between the lots was somewhat greater than 

 it was before the two cows were removed. There was a differ- 

 ence in fat in favor of Lot 2 which at least partly counterbal- 

 anced the difference in milk. 



The two lots stood in the same line of stalls and were treat- 

 ed in every way alike except in the rations fed. Previous to 

 starting the test they were all on the same well-balanced ration, 



