ENERGY IN FEEDINGSTUFFS AND ITS USES 101 



making this deduction corresponds to the net energy of the 

 feed. 



The amount of net energy in a f eedingstuff is obtained by 

 determining by means of the respiration calorimeter the 

 increased amount of energy expended by the animal after 

 consuming the feedingstuiTs, and subtracting this increase 

 from the metabolizable energy. The result is the net energy. 

 Armsby has found that only 55 to 70 per cent of the metab- 

 ohzable energy of the ration may be utihzed for maintenance 

 and for productive purposes. As yet the net energy values 

 of only 15 or 18 feeds have been actually determined, omng 

 to the great expenditure of money, time, and labor necessary 

 in their determination. However, Armsby and Fries ^ and 

 Kellner ^ have worked out a method by which the net 

 energy values of feedingstuffs may be calculated with some 

 degree of accuracy. The net energy values of the common 

 feedingstuffs as calculated by Armsby are given in Table 

 31, of the Appendix. These values are fairly accurate for 

 these feeds when fed to cattle, sheep, and horses, but they 

 have little value in case of hogs. 



Net Energy Value of Nutrients. — In general, the average 

 net energy values of the digested nutrients expressed in 

 therms per pound are approximately as follows : protein, 

 1.02; carbohydrates, 1.00; and fat, 2.25. Thus for the 

 production of energy, protein and carbohydrates have 

 practically the same value, while fat is about 2j times as 

 valuable. 



Work of the Voluntary Muscles. — Any surplus of net 

 energy above the maintenance requirement and, in special 



1 Penn. Exp. Sta. Bui. 71 ; Jour. Agr. Res., Ill, 6, p. 486, 



2 "Scientific Feeding of Animals," p. 82. 



