3 22 



NUTRITION OF FARM ANIMALS 



the withdrawal of these materials tends to increase the protein 

 katabolism, and as regards maintenance or submaintenance 

 rations the two statements are equivalent. But even in the 

 case of supermaintenance rations it has been found that the 

 addition of a surplus of fat or, in particular, of carbohydrates, 

 to a ration containing more than the minimum of protein tends 

 to reduce the protein katabolism to a lower level. The effect 

 is well illustrated, for example, by those of Kellner's respiration 

 experiments on cattle 1 in which starch was added to basal 

 rations which were themselves sufficient to cause some fattening. 

 The following table compares the urinary nitrogen upon the 

 basal ration with that upon the augmented ration : 



TABLE 59. EFFECT OF STARCH ON PROTEIN KATABOLISM OF CATTLE 



It has likewise been shown that this effect is produced not 

 only by the true fats and by the soluble hexose carbohydrates, 

 such as starch and the sugars, but likewise by the pentoses and, 

 in the case of herbivorous animals, by those ill-known ingredients 

 of feeding stuffs, especially of the crude fiber and the nitrogen- 

 free extract, which disappear in the passage of the feed through 

 the alimentary canal and which are commonly spoken of as 

 being digested. This statement covers also the organic acids, 

 whether resulting from -the fermentation of the carbohydrates 

 or contained in the feed. 



409. Protein katabolism depends chiefly on supply. It 

 should be clearly understood that even in the presence of a 

 surplus of fat or carbohydrates the dependence of the protein 



1 Landw. Vers. Stat., 53 (1900). 



