282 NUTRITION OF FARM ANIMALS 



Each pound of dry matter of the hay decreased the loss of energy 

 from the body by 502 Cals. The ration of 10.21 Ib. still 

 permitted a loss from the animal of 268 Cals. To reduce this 

 loss to zero would obviously require the addition of 268 - 502 

 = 0.53 Ib. and an exact maintenance ration as regards energy 

 would have been 10.21 + 0.53 = 10.74 pounds of the hay. 

 In precisely similar fashion the metabolizable energy required 

 for maintenance was 



9544 + 268 X fjjf = 10042 Cal. 



374. Computation of the fasting katabolism. Another 

 method of comparison, however, is of greater significance, since it 

 affords results of more general, value and also serves to bring out 

 clearly the relations between the net energy values of feeding 

 stuffs, the fasting katabolism and the maintenance requirement. 



In the foregoing experiments each pound of hay withdrawn 

 from the ration caused the heat production to decrease by 

 433 Cals. If, then, all the hay were withdrawn from Period 3 

 and the animal reduced to the fasting state, the heat production, 

 or in other words the fasting katabolism, would be 



8064 - (433 X 6.17) = 5392 Cals. 



The same result may also be computed from the losses of 

 energy suffered by the animal. The withdrawal of each pound 

 of hay increased this loss by 502 Cals. The withdrawal 

 of all the 6.17 pounds of Period 3, therefore, would increase 

 the loss by 502 X 6.17 = 3096 Cals., making a total loss 

 of 5392 Cals., equal to the fasting katabolism. In other 

 words, by such a comparison as the foregoing it is possible to 

 determine indirectly the fasting katabolism, which it is scarcely 

 practicable to determine directly. 



It was shown in Chapter VII (344), however, that the fast- 

 ing katabolism is the measure of the maintenance requirement. 

 To maintain the steer of this illustration it would be necessary 

 to supply in his feed an amount of energy, after deducting the 

 losses in the excreta (i.e., an amount of metabolizable energy), 

 equal to the fasting katabolism, 5372 Cals., plus a sufficient 

 additional amount to offset the additional heat production 

 which the consumption of the feed would inevitably occasion, 

 i.e., the work of digestion. 



