THE DIGESTIBILITY OF FEEDING STUFFS. 511 



of the air-dry, finely-ground feeding stuff be digested at body tempera- 

 ture with r>00 cc. of acid pepsin solution for 48 hours, increasing the 

 hydrochloric acid every 12 hours so that at the end of 30 hours it shall 

 be equivalent to 1 per cent. 1 



AMOUNT OF FOOD. 



As to the effect of the amount of food on its digestibility in the ali- 

 mentary canal, it is safe to conclude from the experiments of Henne- 

 berg and E. von Wolff in feeding rations of various amounts of meadow 

 hay, alfalfa hay, and clover hay to steers and sheep that the amount of 

 food may vary within quite wide limits without appreciably affecting 

 the digestibility. 



FODDER MIXTURES. 



The case is different with regard to the fodder mixture, i. e., the 

 proportion of the separate nutrients in the ration. A large number of 

 feeding experiments have shown that the digestibility varies with the 

 percentage of protein in the ration. According to experiments by E. 

 Schulze and M. Maercker with maize gluten, Stohmann with lupines, 

 and the writer with tisli meal, lupines, and soy beans, the addition to 

 the ration of these feeding stuffs rich in protein effects a somewhat 

 better digestibility of the crude fiber and nitrogen-free extract of the 

 rest of the ration. In fact, in some experiments nonalbuminoid protein, 

 as asparagiu, has shown such an effect. 



On the other hand, an increase of the carbohydrates in the ration is 

 accompanied by the reverse effect; the digestibility of the crude fiber 

 and the nitrogen-free extract diminishes, and a somewhat larger amount 

 of nitrogen in the form of secretions (mucin, biliary products, etc.) 

 appears in the feces than when the same ration is fed without the addi- 

 tion of carbohydrates. Numerous experiments by Henneberg, E. 

 Schulze and M. Maercker, G. Kiihn, Stohmann, and others have thrown 

 light upon this point. 



An increase of the fat in the ration appears, from the observations 

 made, to have no effect on the digestibility of the other constituents of 

 the food. Possibly the action of a one-sided increase of the protein in 

 increasing the digestibility and the reverse action of the carbohydrates 

 is due to the favorable effect on the development of different kinds of 

 bacteria, which play an important though different part in digestion. 



Concerning the extent of the so-called depression in digestibility due 

 to carbohydrates, and of the increase of digestibility due to protein, 

 the investigations thus far made only admit of the very general deduc- 

 tion that the larger the amount of nitrogen-free materials added and 

 the more the nutritive ratio is widened, the greater the amount of crude 

 fiber and nitrogen-free extract which remains undigested, and vice 



1 Laiidw. Vers. Stat., 44 (1894). p. 188; 46 (1895), p. 193 (E. S. R., 6, p. 12, and 7, 

 p. 553). 



11931— No. 6 2 



