1 76 Journal of Agricultural Research voi x, no. 4 



as construction and control through antagonism as to make it seem 

 futile to attempt an expression of absolute requirements when natural 

 foods, with their diversity of mineral content, are involved. Even the 

 recognition of differences in the quality of proteins and their relation to 

 nutrition (3, 8, 14) will make it more difficult to continue expressing 

 protein requirements in exact quantities than before the development 

 of such knowledge; and what can be said of the quantitative require- 

 ments of fat-soluble A and water-soluble B and their supply in feeding 

 materials ? 



All these developments of the last few years emphasize the need of a 

 thorough study of the contributing nutritive factors of a single food- 

 stuff, and in the state of our present knowledge such information will be 

 secured only by physiological tests involving the animal in reproduction 

 and milk secretion. A contributing factor by a natural food may at 

 times be in the nature of toxicity and this may serve as a harmful and 

 abnormal factor. As such knowledge develops and it becomes clear that 

 this or that single food material will supply adequately the normal nutri- 

 tive factors not measurable by any quantitative chemical method, such 

 as fat-soluble A, water-soluble B, or mineral nutrients, then we will 

 return with more confidence to the mathematical standard that involves 

 only the energy and protein supply of that single food material. This 

 confidence in the expressed quantities of energy and protein available in 

 a foodstuff will rest upon the definite information that they become 

 physiologically effective only when they form part of a ration which 

 carries one or a number of foodstuffs supplying adequately the other 

 nutritive factors. With such an understanding the feeding standards 

 developed on the energy-protein basis would continue to be theoretically 

 sound and of very great practical value. As illustrative of our position, 

 and taken from our own experience with wheat-grain feeding, we would 

 feel reasonably safe if a wheat-grain ration, based on protein and energy 

 and to be fed continuously to a growing herbivorous animal, was built 

 around alfalfa hay, less safe if built around com stover, and fearful of 

 disaster should the roughage used be wheat straw. These facts should 

 emphasize the very great necessity for the accumulation of information 

 on the nutritive value of single foodstuffs, and it is apparent that such 

 information will become very valuable in the future use of the protein- 

 energy standards. Such knowledge will not destroy, but will supple- 

 ment the feeding standards of the present time and secure more confi- 

 dence in their use. 



EXPERIMENTAL WORK 



GROWTH ON WHEAT AND CORN RATIONS 



For purposes of locating the deficiencies of the all-wheat-plant ration 

 (wheat grain, wheat gluten, and wheat straw), which had given fair 

 growth, but was a failure in reproduction with grade vShorthorn heifers, 



