March, 1928] 



AGRICULTURAL EXPERIMENTS 1927 



13 



DISCOVERING THE BASE-LINE OF ANIMAL NUTRITION 



The determination of the feed level needed to hold animals at mere 

 maintenance — that is, a condition where there is neither gain nor loss in 

 body tissue — is of fundamental importance to an understanding of animal 

 nutrition. 



This has been one of the principal objects of the studies conducted in 

 co-operation with the Nutrition Laboratory of the Carnegie Institution of 

 Washington, using the new type of respiration chamber designed by Dr. 

 F. G. Benedict. Messrs. Benedict and Ritzman have studied steers while 

 fasting and while on different levels of subsistence, ranging from undernu- 

 trition to heavy fattening rations. They find that when the food supply is 

 below maintenance requirements, or when it is entirely cut off, the demand 

 for energy to maintain life is thrown on the organism itself to meet this 

 deficiency. Thus profound changes may be expected in the adaptation 

 of vital activities to this new situation. Life itself now becomes a 

 defensive scheme, and readjustments are made to secure a minimum 

 demand upon existing stores of energy. 



Incidentally, these studies demonstrate that steers may be carried 

 through a period of three or four months on extraordinarily low rations 

 without affecting their general health or lessening their power to regain a 

 suitable market condition with subsequent liberal feeding — a conclusion 

 of practical value to the stockman. 



The important fact, however, that the bovine has a remarkable capacity 

 to accelerate or to slow down its vital activities in accordance with the 

 available supply of food has given an entirely new basis of attack on the 

 problem of basal requirements for maintenance. 



These basal requirements — an economic overhead in feeding live stock 

 — form the only logical foundation for comparison of the relative heat or 



Cattle in metaljolism stalls used in studies of animal nutrition. 



