2 5 2 



NUTRITION OF FARM ANIMALS 



337. Influence of body fat. E. Voit's compilation (335) 

 likewise showed clearly that the ratio of protein to total katab- 

 olism in fasting may vary considerably as between individuals, 

 depending on the relative amount of fat contained in the body. 

 So long as body fat is readily available as fuel, the amount of 

 protein katabolized remains relatively small, but if the animal is 

 originally deficient in fat, or if its content of fat becomes much 

 reduced during fasting, more protein is katabolized to make up 

 for the deficiency. 



Usually, the store of fat in the body is less than that of protein, 

 while in fasting its exhaustion is relatively more rapid. There comes 

 a time, therefore, when the supply of non-nitrogenous material to the 

 tissues begins to flag. When this happens, the protein katabolism 

 begins to increase ; that is, when the supply of reserve fuel material 

 runs low, the organism begins to use more of the protein of its tissues 

 as a source of energy, and Voit x has shown that this occurs whenever 

 the ratio of fat to protein remaining in the body falls below a certain 

 limit. If the animal was originally well nourished, this rise in the 

 protein katabolism occurs only shortly before death, from which it 

 has received the name premortal rise. In the case of very fat ani- 

 mals this point may never be reached, while, on the other hand, in a 

 lean animal the protein katabolism may increase steadily from the 

 very beginning of the fasting. The following three experiments 

 upon a fat guinea pig, a medium fat dog and a lean rabbit, cited by 

 Voit from Rubner's experiments, serve to illustrate these three types 

 of fasting katabolism. 



TABLE 31. FASTING PROTEIN KATABOLISM OF FAT, MEDIUM AND THIN 



ANIMALS 



1 Ztschr. Biol., 41 (1901), 502. 



