NUTRITION OF FARM ANIMALS 



Net energy values for fattening 



448. General conception. Physiologically, the process of 

 fattening may be regarded as a storing up by the animal, against 

 a possible future scarcity, of feed energy supplied in excess of 

 its immediate needs. 



This storage of .energy is not accomplished without some loss. 

 As in maintenance feeding, so in fattening, a considerable 

 portion of the feed energy escapes utilization for one reason or 

 another. The conception of the net energy value as express- 

 ing that part of the feed energy which remains available after 

 these various losses have been deducted, has been considered 

 in Chapter VIII. The same conception may be extended to 

 fattening rations. Just as the net energy value of a feed for 

 maintenance is measured by the loss of body energy which it 

 prevents, so its net energy value for fattening is measured by 

 the storage of body energy brought about. 



449. Method of determination. This conception, as well 

 as the method of determining the net energy value for fatten- 

 ing, may be illustrated by the following respiration experiment 

 by Kellner upon a mature ox, in which meadow hay was added 

 to a mixed basal ration already sufficient to cause some gain. 

 The second column of the table shows the metabolizable energy 

 of the two rations, the third column the computed heat pro- 

 duction, and the fourth the energy contained in the observed 

 gain of protein and fat. 



TABLE 72. DETERMINATION OF NET ENERGY VALUE FOR FATTENING 



Each pound of hay added to the basal ration resulted in a 

 gain of protein and fat containing 0.288 Therm of energy. 



