286 THE FEEDING OF ANIMALS 



as a means of determining what should be the relative 

 market cost. 



382. Conditions involved in the selection of feeding- 

 stuffs. Much useful knowledge is available to the 

 stock-feeder as a means of guiding him to an economical 

 selection. Some of the important facts to keep in mind 

 are: Some feeds carry more nitrogenous matter than 

 others; some feeds are largely carbohydrates; cereal 

 grains contribute to the ration much the same compounds 

 in much the same proportions; the variations of composi- 

 tion among the waste products that are in the market as 

 commercial feeds; how the coarse food's differ among 

 themselves and from the grains; some feeds are better 

 adapted than others to a certain class of animals, even 

 though of essentially the same composition, and what 

 practice and science have taught concerning the mixtures 

 necessary to secure an efficient combination of nutrients 

 for the work to be done. 



383. Digestibility as a basis for selecting feeding- 

 stuffs. 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. It is clear that the best a feeder can do is to 

 select the feeds that supply the largest quantity of avail- 

 able nutrients for the least money with due reference to 

 the class of nutrients desired. 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 digested, while the digestibility of wheat 

 bran, brewers' grains, and oats is on the average only 



