Nutrition Studies. 



55 



76. Feeding fats and carbohydrates only. Kellner 1 points out that 

 when animals are fed exclusively on nitrogen-free nutrients, such 

 as the sugars, starches, fats, etc., the waste of fat from the body is 

 materially lessened, and the waste of the nitrogenous tissues of the 

 body, such as the muscles, is somewhat reduced, tho not entirely 

 stopped. On account of this sparing of the body substances, 

 animals forced to live on such diet survive longer than those 

 wholly deprived of food. Yet because of the continuous small 

 waste of protein from the tissues of the body, animals nourished 

 solely on fats and carbohydrates cannot long survive. 



77. Feeding fats and carbohydrates with protein. Experiments 

 by Voit 2 with dogs, and Kellner 3 with oxen, show that when animals 

 are fed fats or carbohydrates in addition to protein, the nitrogen 

 waste depends in some measure upon, but does not necessarily keep 

 pace with, the amount of nitrogen supplied in the food, since the 

 fats and carbohydrates protect the protein in the body from oxida- 

 tion, or spare it, to some extent. The digestible portion of the 

 crude fiber, and likewise in all probability the pentosans, decrease 

 the waste of nitrogen in some degree, as do the more easily digested 

 sugars and starches. 



When an excess of protein is supplied an animal, the nitrogen 

 waste is greatly increased, as the following experiment by Lawes 

 and Gilbert 4 shows. One of 2 pigs which were similar in weight 

 and appearance was given all it would consume of lentil meal, 

 which contains about 25 per ct. of crude protein. The other was 

 fed an unlimited ration of barley meal, containing about 12 per 

 ct. of crude protein. The nitrogen consumed in the food and ex- 

 creted as urea was as follows : 



Effect of an excess of protein on the nitrogen excretion. 



The table shows that the pig receiving lentil meal consumed more 

 than twice as much nitrogen as the one fed barley meal. It also 



1 Ernahr. landw. Nutztiere, 1907, p. 125. 



2 Ztschr. Biol., 5, 1869, pp. 352, 431. 



3 Landw. Vers. Stat., 53, 1900, pp. 124, 210, 316. 



* Jour. Eoy. Agr. Soc., 1895; U. S. Dept. Agr., Office Expt. Sta., Bui. 22. 



