NUTRITIVE VALUE OF FEEDING STUFFS 43 



Net Energy Values of American Feeding Stuffs. — Armsby and 

 Putney have calculated, by the method just described, the net 

 energy values of the more important American feeding stuffs based 

 on the compilations of chemical analyses and digestible components 

 of feeding stuffs by Henry and Morrison. The results of these cal- 

 culations, including data for digestible true protein, are given in 

 Table III of the Appendix. In connection with this table it should 

 be stated, first, that both the data for the digestion coefficients and 

 for the expenditure of energy due to feed consumption are derived 

 exclusively from experiments on ruminants (in the latter case on 

 cattle) ; second, the table shows primarily the net energy values for 

 maintenance or fattening. There seems good reason for believing, 

 however, that they may be taken without serious error to represent 

 also the net energy values for growth and at least the relative values 

 for milk production. It is also believed that the same net energy 

 values may be regarded as expressing with sufficient accuracy the 

 relative values of feeding stuffs for horses and for swine. 5 



The net energy values of feeding stuffs, as determined directly 

 by means of respiration experiments or computed by the method 

 explained, furnish important information as to the value of the 

 different feeds for the nutrition of farm animals, especially rumi- 

 nants. These values axe preferred by many to the figures showing 

 the digestible components of feeds and they appear to be coming 

 into more general use. Both methods have their merits 'and they 

 supplement each other; hence students should understand how the 

 two sets of figures have been obtained, and should become familiar 

 with both methods of experimentation and of obtaining relative 

 values of feeding 'stuff s. 



QUESTIONS 



1. Give an outline of the method of conducting digestion trials. 



2. What is a coefficient of digestibility? 



3. What is a Calorie? A therm? 



4. Describe a calorimeter. 



5. Describe the respiration apparatus. 



6. Describe the respiration calorimeter. 



7. How is a gain in muscular tissue and in body fat in the animal body 



determined ? 



8. What is meant by the chemical energy of a feeding stuff? 



9. What is the difference between chemical and available energy ? 



10. Why are coarse feeds less valuable to farm animals than concentrates? 



11. What are net energy values, and how have they been obtained. 



12. For which class of farm animals are the energy values especially 

 applicable. 



* U. S. Dept. Agr. Bui. 459. 



