2 7 2 



NUTRITION OF FARM ANIMALS 



olizable energy of the hay and the heat production per day, 

 determined in the manner illustrated in Chapter VI (322, 329), 

 were as follows : 



TABLE 37. DETERMINATION OF NET ENERGY VALUE OF TIMOTHY HAY 



The 4.04 pounds of hay (water-free), added to the insufficient 

 ration of Period III diminished the loss of energy from the 

 body of the animal by 2028 Cals. ; that is, they contributed 

 this amount towards its maintenance. The net effect of the 

 hay, therefore, computed exactly as in the supposed case of 

 the dog in the preceding paragraph, was 2028 -f- 4.04 = 502 

 Cals. per pound of dry matter. But the added hay contained 

 metabolizable energy to the amount of 935 Cals. per pound of 

 dry matter. Clearly, therefore, by no means all of the metab- 

 olizable energy of the hay could be utilized for maintenance 

 by the steer. Only 502 Cals. were used for this purpose, in 

 place of energy previously derived from the katabolism of 

 the fat and protein of the body, while the remaining 433 Cals. 

 were, indeed, metabolized in the body, but resulted simply in 

 increasing the heat production by this amount. 2 The propor- 

 tion of the metabolizable energy of this hay which was available 

 for maintenance, then, was 502 -r- 935 =53.7%. The fore- 

 going result is typical of a large number of others which have 

 been reached in experiments on various species of animals. 



1 Since submaintenance rations were fed, the gains were of course negative, 

 i.e., chemical energy was lost from the body. 



2 Since gains of energy are computed from the difference between income and 

 outgo, the figures of the last column of the table necessarily agree with those of the 

 two preceding ones. They simply present a different aspect of the same facts. 



