46 



PRINCIPLES OF FEEDING FARM ANIMALS 



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). Fats yield about 2.25 times as much 

 energy on combustion as starch, and this factor has been commonly 



FIG. 9. A view of the respiration calorimeter at the Pennsylvania Experiment Sta- 

 tion. The calorimeter chamber in which the animal on the experiment is kept, to the left. 

 (Armsby.) 



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 rest is inert matter, passing through the 

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



