COMPOSITION OF FEEDING STUFFS. 217 



Digestibility of foods. Only a certain portion of a feeding stuff 

 is of actual value to the animal, viz., the portion which the diges- 

 tive juices of the animal can render soluble, and thus bring into 

 a condition in which the system can make the use of it called for; 

 this digestible portion ranges from one-half or less to more than 

 96 per cent, in case of highly digestible foods. The rest is simply 

 ballast, and the more ballast, i. e., the less of digestible matter a 

 food contains, the more the value of the digestible portion is re- 

 duced. Straw, e. g., is found, by means of digestion experiments, 

 to contain between 30 and 40 per cent, of digestible matter in all, 

 but it is very doubtful whether an animal can be kept alive for any 

 length of time when fed straw alone. It very likely costs him 

 more effort to extract the digestible matter therefrom than the 

 energy this can supply. An animal lives on and produces not from 

 what he eats but from what he digests and assimilates. 



Relative value of feeding stuffs. Since the prices of different 

 feeding stuffs vary greatly with the locality and season, it is im- 

 possible to give definite statements as to the relative economy 

 which will always hold good; it may be said, in general, that the 

 feeding stuffs richest in protein are our most costly and at the 

 same time our most valuable foods. Experience has shown to a 

 certainty that a liberal supply of protein is an advantage in feed- 

 ing most classes of farm animals, so that if such feeding stuffs 

 can be obtained at fair prices, it will pay to feed them quite ex- 

 tensively, and they must enter into all food rations in fair quanti- 

 ties in order that the animals may produce as much milk, meat, 

 or other farm products, as is necessary to render them profitable 

 to their owner. The following statement shows a classification of 

 feeding stuffs which may prove helpful in deciding upon kinds and 

 amounts of feeds to be purchased or fed: 



