NUTRITIVE VALUE OF FEEDING STUFFS 49 



amounts of the energy value are obtained for productive purposes. 

 Animals that have to subsist on only such feeds for any length of 

 time will lose flesh, since there is not a sufficient amount of energy 

 left to meet the needs of the body after that required for the diges- 

 tion of the feed is taken out. 



The weak point in the old system of basing the nutritive values 

 of different feeding stuffs on their contents of total digestible 

 components is that it does not take into account the differences in 

 the amount of energy required for the work of digestion and assimi- 

 lation of feeds of different kinds. Where this work does not differ 

 greatly, however, as between different feeds of the same kind, 

 either green feeds, dry roughage, or concentrates, the error intro- 

 duced is not, generally speaking, of much importance. The im- 

 mense amount of work done in the study of the composition and 

 digestibility of different feeding stuffs makes the data obtained 

 along these lines most valuable and fully justifies their continued 

 use in practice and for the study of the comparative value of feed- 

 ing stuffs. 



Kellner's Starch Values. The system of comparison of dif- 

 ferent feeding stuffs elaborated during the early part of the century 

 by the German agricultural chemist, Kellner, is based on the re- 

 sults of extensive feeding and respiration trials with mature fatten- 

 ing steers. Kellner fed such steers basal rations barely sufficient 

 to maintain them at an even body weight, and added to these 

 either pure nutrients, like starch, sugar, oil, etc., fed separately 

 or combined, or different feeding stuffs whose nutritive effect was 

 studied. He thus found that one pound of digestible components 

 was capable of producing the following amounts of body fat : 



1 pound pure starch or digestible fiber, 0.248 pound body fat. 



1 pound sucrose, 0.188 pound body fat. 



1 pound protein, 0.235 pound body fat. 



1 pound fat or oil, 0.474 to 0.598 pound, according to its 



A large number of trials were made to determine whether the 

 digestible components of ordinary feeding stuffs gave similar re- 

 sults as corresponding amounts of the various groups of nutrients 

 fed in pure form. In the case of a number of feeding stuffs this 

 was actually found to hold true; e.g., for many oil ideals, corn, 

 rice polish, red dog flour, potatoes, buckwheat middlings", and ani- 

 mal feeds. With most feeds, however, the amou^fef fat which 

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