274 The Feeding of Animals 



the ration much the same compounds in much the 

 same proportions, and he will understand the varia- 

 tions of composition among the waste products that 

 are in the market as commercial feeds. He will learn 

 how the coarse foods differ among themselves and 

 from the grains. Practice and observation will teach 

 him that some feeds are better adapted than others to 

 a certain class of animals, even though of essentially 

 the same composition. In his efforts to compound 

 rations he will not only have regard for this adapta- 

 tion, but he will keep in mind what practice and sci- 

 ence have taught concerning the mixtures necessary 

 to secure an efficient combination of nutrients for the 

 work to be done. 



After all this is understood, there may be several 

 feeds which are essentially alike in composition and 

 nutritive function but which have different prices, and 

 there still remains the problem of selecting the most 

 economical. If a feeder wishes for carbohydrates, 

 from what source should he purchase them ? If he 

 needs protein should he select gluten meal, one of 

 the oil meals, or some other of the nitrogenous by- 

 products ? It is clear that the best he can do is to 

 select the feeds that supply the largest quantity of 

 available nutrients for the least money. If all the 

 feeding stuffs were digested in equal proportions there 

 would be no need of considering digestibility, but this 

 is not the case. Large differences in digestibility exist. 

 From 86 to 88 per cent of the dry matter of the 

 cereal grains, oats excepted, is dissolved by the diges- 

 tive juices, while the solubility of wheat bran, brewer's 



