New York AoRrcuLTURAL Experimext Station. 31 



with three other cows and the data thus obtained not only fur- 

 nish additional evidence concerning the main question of the 

 source of milk fat but have been used in studying other ques- 

 tions relating to the metabolism of the milch cow. The publica- 

 tion of the results secured has been much delayed, largely 

 because of the great amount of work involved in the 

 investigations. 



THE PLAN, MATERIALS AND PROCEDURE OF THE 



EXPERIMENTS. 



THE FORMER EXPERIMENT. 



In the experiment previously reported the cow was fed a nor- 

 mal ration for a time; then, for 95 days, she was given foods 

 that, because of extraction, contained very small proportions of 

 ether extract. 



During 66 days the solid and liquid excreta were collected for 

 analysis and daily analyses of the milk were made for a longer 

 period. The quantity of the ration and the nutritive ratio were 

 varied in a way calculated to show the influence of the protein 

 supply upon fat secretion. The experiment was so planned as to 

 make it impossible for the milk fat to have its source wholly in 

 the protein and ether extract of the food and so long continued 

 that any material draft upon the body of the cow for milk pro- 

 duction would produce a marked change in the condition and 

 weight of the animal. (For details see Bulletin 132.) 



THE NEW EXPERIMENT®. 



The later experiments involved the use of three cows quite 

 unlike in their characteristics and productive capacity, each of 

 which received a ration distinctly different from the rations 

 given the other two. 



(1) Cow 12, a grade Shorthorn weighing about 1,200 pounds, 

 fresh in milk at the beginning of the experiment and not preg- 

 nant, was fed for 88 days a ration containing little ether extract, 

 the nutritive ratio being very gradually varied from narrow to 

 wide and back again, the total quantity of digestible dry matter 

 consumed daily being maintained at a fairly uniform quantity. 



