328 MANAGEMENT AND BREEDING OF HORSES 



terial passes along still furthet complete the process, 

 although a part of the food escapes digestion and passes 

 out in the feces. During its course along the digestive 

 ti'act, the digested material is absorbed and received into 

 the vessels, through which it is distributed to the various 

 parts of the body. 



Digestible nutrients. — These are parts of the food ma- 

 terials that are digested and used by the animal. The 

 amount of the food thus digested depends on the kind of 

 food, the amount fed, the condition of the animal and 

 like factors. Of the various food rpaterials, the carbo- 

 hydrates are the most digestible, vi^hile fiber is the least 

 digestible, and betw^een these lie fat and protein. As a 

 rule, the fat is more digestible than the protein. In gen- 

 eral the digestibility of a food decreases when exceed- 

 ingly large amounts are fed. On the other hand, a 

 greater digestibility cannot be secured by limiting the 

 consumption below the normal amount demanded by the 

 animal. In general, thrifty animals digest their food 

 more thoroughly than those in poor health. 



Since the digestible nutrients are the only food mate- 

 rials that the animal can appropriate to its use, it is with 

 them that the feeder is concerned in choosing food for a 

 ration. Much work has been done by the various ex- 

 periment stations to determine the digestibility of foods. 

 To show at a glance the amount of digestible nutrients 

 contained in the various foods. Table VIII is published 

 in the Appendix of this book (p. 448). 



Conditions favoring digestion. — The changes that take 

 place in the food materials during the process of diges- 

 tion are very complex and proceed in accordance with 

 fixed laws. While these changes are largely beyond the 

 control of the feeder there are certain conditions that 

 favor the completeness of digestion, chief of which are 

 time of harvesting and method of curing hay as well as 

 the grinding and wetting of certain kinds of foods. 



The time to harvest hay, so as to get the maximum 



