1 68 NUTRITION OF FARM ANIMALS 



carbohydrate metabolism may be schematically expressed 

 thus : - 



Glycogen $ Dextrose ^\ 



X* (" Lower fatty acids -> CO 2 and H 2 O 

 Proteins ^ Amino acids $ 1 



INHs- >Urea 



236. Formation of fat from proteins. Since the non-nitrog- 

 enous products of protein katabolism appear to consist largely 

 of comparatively simple substances closely related to the lower 

 members of the fatty acid series, and since some at least of 

 these may in all probability be synthesized to carbohydrates, 

 while the latter can undoubtedly give rise to fats, it is natural 

 to conclude that the non-nitrogenous products of protein 

 katabolism may serve as a source of fat, either by direct syn- 

 thesis of the simpler fatty acid chains or possibly by way of 

 the carbohydrates. The conclusion is one which has been 

 hotly debated and much of the earlier evidence in its favor 

 has been shown to be inconclusive. The experimental evi- 

 dence may be more conveniently considered in connection with 

 a discussion of the sources of animal fat (247-249). For the 

 present, it may suffice to say that the formation of fat from 

 protein seems altogether probable, but that on the other hand 

 the amount of fat thus formed under normal conditions is 

 usually unimportant. 



5. THE METABOLISM or THE NUCLEOPROTEINS 



The metabolism of the conjugated proteins, with the excep- 

 tion of the nucleoproteins, offers few features of special in- 

 terest. In general it may be said that they are split up into their 

 constituents during digestion and that the cleavage products 

 undergo substantially the same metabolic changes as if con- 

 sumed by the animal in the uncombined form. In the case of 

 the nucleoproteins, however, the metabolism of the nucleic 

 acid portion of the molecule calls for more specific consider- 

 ation. 



Anabolism 



237. Fate of digestive products. The nucleic acids undergo 

 extensive enzymatic cleavages in digestion (139), the products 



