ILLINOIS DAIRYMEN'S ASSOCIATION. 199 



PROTEIN REQUIREMENTS. 



By T. L. Haecker, Professor of Dairy Husbandry, Minnesota 

 Dairy School. 



Heretofore our investigations in milk production have been conducted 

 along popular lines to determine the yields of milk and butter fat from 

 various types of cows, cost of production of milk and butter fat, with a 

 few trials, comparing different food stuffs under methods and feeding 

 standards generally employed by our leading teachers, breeders and 

 feeders of cattle, without question as to whether the feeding standards 

 were based upon mere theoretical deduction or whether they were based 

 upon careful, practical demonstration. American literature dealing with 

 feeding domestic animals is largely based upon the teachings of Dr. Emil 

 v. Wolff, an eminent German scientist who, in 1864, published his investi-* 

 gations on the kind and amount of nutrients actually needed by domestic 

 animals in making growth, maintaining the animal body and returning 

 animal products without waste of any of the nutrients. In Wolff's formu- 

 lated feeding standards are given in great detail the amount of organic 

 matter and digestible nutrients needed by animals at various stages of 

 growth and the amounts needed 1 by the mature bovine in meat and milg 

 production. As an illustration, that required by a cow in milk, weighing 

 1,000 pounds, was fixed at 24 pounds of dry matter and of digestible nu- 

 trients, 2.5 of protein, 12.5 of carbo-hydrates and .4 of ether extract or 

 what is commonly termed fat. Some scientists have objected to pre- 

 scribed fixed rules for feeding, because animals vary so much in feeding 

 power and productive capacity and to meet this objection Dr. C. Lehmann, 

 of the Berlin Agricultural College, in 1897 modified the Wolff standard by 

 substituting dry matter for organic matter and varies the digestible nu- 

 trients according to the daily flow of milk. The wisdom of such a change 

 is obvious, for a cow yielding 22 pounds of milk daily certainly needs more 

 protein, other things being equal, than will one yielding only 11 pounds. 



