194 A FEEDER'S GUIDE. 



this purpose, pound for pound, as fat, which also is often 

 used for the purpose by the animal organism, but on ac- 

 count of the large quantities in which the carbohydrates 

 are found in most feeding stuffs they form a group of 

 food materials second to none in importance. Since it 

 has been found that fat will produce about 2V 2 times as 

 much heat as carbohydrates on combustion, the two com- 

 ponents are often considered together in tables of com- 

 position of feeding stuffs and discussion of the feeding 

 value of different foods, the per cent, of fat being multi- 

 plied by 2^ in such cases, and added to the per cent, of 

 carbohydrates (i. e., crude fiber plus nitrogen-free extract) 

 in the foods. As this renders comparisons much easier, 

 and simplifies discussions for the beginner, we shall adopt 

 this plan in the tables and discussions given in this Guide. 



Carbohydrates and fat not only supply heat on being 

 oxidized or burned in the body, but also furnish ma- 

 terials for energy used in muscular action, whether this 

 be voluntary or involuntary. They also in all probability 

 are . largely used for the purpose of storing fatty tissue 

 in the body of fattening animals, or of other animals that 

 are fed an excess of nutrients above what is required 

 for the production of the necessary body heat and mus- 

 cular force. 



To summarize briefly the use of the various food 

 elements: Protein is required for building up muscular 

 tissue, and to supply the breaking down and waste of 

 nitrogenous components constantly taking place in the 

 living body. If fed in excess of this requirement it is 

 used for production of heat and energy. The non-nitro- 

 genous organic components, i. e., carbohydrates and fat, 

 furnish material for supply of heat and muscular exer- 

 tion, as well as for the production of fat in the body or 

 in the milk, in case of milch cows giving milk. 



Digestibility of foods. Only a certain portion of a 

 feeding stuff is of actual value to the animal, viz., the 

 portion which the digestive 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 digesti- 

 ble portion ranges from 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 reduced. Straw, e. .-g., is 

 found, by means of digestion experiments, to contain be- 

 tween 30 and 40 per cent, of digestible matter in all, but 

 it is very doubtful whether an animal can be kept aliTe 



