THE FATTENING OF MATURE ANIMALS 1 361 



This was its net energy value for fattening. A comparison 

 with Table 37 in Chapter VIII (364), showing the results of a 

 determination of the net energy value for maintenance, renders 

 evident the identity of the method employed in the two cases, 

 the only difference being that in one case the comparison be- 

 tween the two rations is made below the point of maintenance 

 and in the other case above it. It is evident that in fattening, 

 as in maintenance feeding, there is a considerable expenditure 

 of energy consequent upon the consumption of feed, so that, 

 only part of the metabolizable energy is actually stored up in 

 the gain by the oody. In the experiment given as an illus- 

 tration, one pound of the hay contained 0.714 Therm of 

 metabolizable energy, of which only 0.288 Therm or 40.7 per 

 cent was recovered in the gain. 



450. Relative values for maintenance and for fattening. - 

 The same causes which were considered in Chapter VIII (367) 

 are of course operative to bring about the increased expendi- 

 ture of energy on the heavier rations of the fattening animal. 

 In addition, it would appear that the chemical changes in- 

 volved in the formation of fat from proteins and carbohydrates 

 would result in more or less evolution of heat. Whatever 

 expenditure of energy may be thus caused is additional to that 

 caused directly by feed consumption under maintenance con- 

 ditions and must evidently tend to reduce the net energy value 

 of the feed by a corresponding amount ; in other words, the net 

 energy values of feeding stuffs for fattening would tend to be 

 lower than those for maintenance. Such data as are available, 

 however, do not appear to indicate that this difference is a 

 considerable one in the case of farm animals, and it would appear 

 that, in the case of cattle at least and presumably in that of other 

 species, the net energy values of feeding stuffs may be regarded 

 as being substantially the same for fattening as for maintenance. 1 



Energy requirements for fattening 



451. Energy content of gain. Since the net energy value 

 of a feeding stuff or ration for fattening, as explained in the 

 foregoing paragraphs, is that part of its total energy which can 

 be stored up by the animal in the increase, it follows that the 



1 Compare Armsby and Fries, Jour. Agri. Research, 3 (1915). 435- 



