422 PRINCIPLES OF AGRICULTURAL CHEMISTRY 



The Productive Value of a Nutrient. As we have previously 

 stated, the quantity of a ration in excess of the maintenance re- 

 quirements of an animal, may be used for productive purposes. 

 If the animal is a fattening animal, this excess may be used for 

 putting on fat. 



Kellner 1 has estimated the fat produced by various nutrients 

 and feeds by the following method. With the aid of the respira- 

 tion apparatus, he determined the income of carbon and nitrogen 

 in the food fed and in the water, and the outgo in the urine, the 

 solid and the gaseous excrements, and so ascertained the quantity 

 of the fat and flesh produced by a basal ration (Period I). This 

 ration was sufficient to maintain the animal and produce a little 

 fat. In Period II, the nutrient or food to be tested, was added 

 to this basal ration and the amount of flesh and fat produced was 

 again determined. The small quantity of flesh gained or lost 

 was in each case calculated to the quantity of fat which would 

 contain an equal amount of energy. The amount of fat gained 

 in Period II less the amount of fat gained in Period I, gives the 

 gain of fat due to the additional food or nutrient fed. The 

 quantity of fat produced by 100 grams of the food or nutrient 

 digested was then calculated from this data. The quantity of 

 fat produced should be in proportion to the kinetic energy of the 

 feed. 



'Experiments were first made with pure nutrients, with the 

 following results : 



Fat produced by 

 100 grams digested 



Cocoanut oil 59.8 



Ether extract of coarse feeding stuffs 47.4 



Ether extract of grasses 52.6 



Starch 24.8 



Cane sugar 18.8 



Lactic acid o.o 



Crude fiber (paper pulp) 25.3 



Proteids (albumen) 24.8 



Pentosans not determined 



1 Landw. Versuchs-stat., 1900, p. 450. See also Arnisby, Bulletin 71, 

 Pennsylvania Station. 



