38 PRINCIPLES OF FEEDING FARM ANIMALS 



The Calorimeter. This apparatus consists of a well-insulated, 

 double-walled compartment, into which a platinum shell or bomb 

 is introduced and submerged in water. A weighed small amount 

 of the substance wihose 'heat of combustion is to be determined is 

 introduced into this shell with compressed oxygen, and ignited 

 by means of an electric .spark. By noting the rise in temperature 

 in the surrounding water the amount of heat given off by the sub- 

 stance on complete combustion can be calculated. 



Chemical Energy. The following are the results of deter- 

 minations of the chemical energy of different classes of nutrients 

 and feeding stuffs: 



Chemical Energy in 100 Pounds, in Therms 



Pure nutrients 

 Protein : Carbohydrates : 



Wheat gluten 272 Starch, cellulose 190 



Gliadin, serum albumen . . 268 Glucose 170 



Egg albumen, pure lean Sucrose, lactose, maltose . 179 



meat . . 259 Fats : 



Blood fibrin 256 Steers and swine 425 



Sheep 427 



Corn oil 421 



Common feeding stuffs 



Flaxseed meal 267 Timothy hay 175 



Linseed meal 197 Clover hay 173 



Oats 181 Oat straw, wheat straw, 



Wheat bran 176 cornmeal 171 



Rice meal 170 



The figures given in the table show the amounts of chemical 

 energy (in therm units) which are set free when 100 .pounds of 

 different pure nutrients and common feeding stuffs are completely 

 burned. We note that the figures range for protein from 256 to 

 272 therms, for carbohydrates from 170 to 190, and for fats from 

 421 to 427, while those for feeding stuffs vary from 170 (rice 

 meal) to 267 (flaxseed meal). It will be seen that fats yield close 

 to 2.25 times as much energy on combustion as starch, and this fac- 

 tor has been commonly adopted for the heat-producing value of fats 

 as compared with that of starch and of carbohydrates in general. 



The figures given represent the total potential energy that is 

 locked up in the materials, but they do not show the energy that is 

 available to animals fed the different feeding stuffs or nutrients. 

 The reason for this is three-fold : 



First, feeding stuffs are never completely digested by animals, 

 as has been shown; only the digestible portions furnish energy for 

 physiological uses: the resit is inert matter, passing through the 

 animals and of no direct value to them, except possibly in regulat- 

 ing the bowels. The less digestible matter in a feed, the lower is 

 therefore, its value to animals. 



Second, there are certain losses through fermentations in the 



