4O2 PRINCIPLES OF AGRICULTURAL CHEMISTRY 



it may digest less. In Kuhn's method, 2 grams of feeding-stuff 

 are treated with I gram of pepsin dissolved in 500 cc. of 0.2 per 

 cent, hydrochloric acid, maintained at the blood heat 48 hours, 

 and the hydrochloric acid increased from 0.2 to i.oo per cent, by 

 additions of acid at intervals of 12 hours. The residue is then 

 filtered oft", washed, nitrogen determined in it and calculated to 

 protein. 



Influence of Different Conditions on Digestion. The digestion 

 of food depends upon a number of conditions. The kind, variety, 

 and age of the animal, composition of the rations, the prepara- 

 tion of the food, and other circumstances, have been studied by 

 proper arrangement of the experiments. 



Kind of Animal. Differences in the digestive organs, digestive 

 secretions, and habits of animals make considerable differences 

 in their digestive power. The digestive organs of sheep and 

 goats are twenty-seven times as long as their bodies ; of the ox, 

 twenty times; of pigs, fourteen times; and of the horse, eleven 

 times. Ruminants have greater ability to digest coarse fodders 

 than other animals. Sheep digest less than cattle, particularly of 

 coarse fodders which are hard to digest, apparently because the 

 contents of the last intestinal tract of cattle is more moist and the 

 process of fermentation continues longer. The more digestible 

 the material, the less the difference. 



On account of shorter intestines and simpler organization of 

 the stomach, the horse has a less digestive power than ruminants, 

 especially for coarse fodders. The horse digests only about half 

 as much from straw as does the ox. The difference is most 

 marked with crude fiber and ether extract; there is little differ- 

 ence in protein, especially in concentrated feeds. 



Pigs have less digestive power than horses or cattle for green 

 feeds, and by-products containing much crude fiber. With grain 

 and oil cakes the difference is less ; but there are many by- 

 products, such as brewers grains, which the pig digests poorly. 



The following experiments were made to compare animals of 

 different kinds, fed on the same fodder: 



