36 



PRINCIPLES OF FEEDING FARM ANIMALS 



toward the end of the last century, our theories of these problems 

 and the science of animal nutrition rested almost wholly on the 

 knowledge of the feeding stuffs gained through chemical analyses 

 and digestion trials. 



Coefficients of Digestibility. The average digestion coeffi- 

 cients for the more important American feeding stuffs as determined 

 in digestion trials with ruminants, are given in Appendix Table II. 

 Complete compilations of digestion coefficients determined for 

 .American feeding stuffs with different classes of farm animals will 

 be found in several U. S. Department of Agriculture and State pub- 

 lications, as well as in standard reference books on the subject ; these 

 compilations also give the number of separate trials conducted and 

 the number of animals experimented with in each case, as well as 

 the variations in the results of the separate trials. 1 The following 

 table shows the digestion coefficients for a few representative feeds : 

 Digestion Coefficients for Ruminants 



B. THE ENERGY OF FEEDING STUFFS 



The feeds which animals eat are directly or indirectly derived 

 from plants. During their growth plants store up chemical energy 

 in the stems, leaves and fruit, which becomes available as food for 

 man and beast. This latent or potential energy in plant materials 

 is again set free on combustion (oxidation) and is utilized by the 

 animals in one or more of three ways, either directly as kinetic 

 energy for maintenance of body heat, or transformed into motion 

 as mechanical energy for doing mechanical work, or changed into 

 chemical energy. If the energy supplied in the feed is more than 

 sufficient to cover the demands for the first two purposes given, the 

 excess may be stored up in the body as chemical energy in the form 



1 Bulletin 77, Office of Experiment Stations; Massachusetts Report, 

 1912; Bui. 152, 158, 181; Henry-Morrison, "Feeds and Feeding," p. 647; 

 Jordan, "The Feeding of Animals," Rev. Ed., p. 443; Mentzel and v. 

 Lengerke, Ldw. Kalender. 1916. 



