18 FEEDS AND FEEDING 



and combine it with carbon to form carbonic acid gas, which is thrown 

 off as waste in the breath. Thus the two great classes of life are inter- 

 dependent. 



In the animal body the organic material derived from plants may be 

 built into still other highly organized compounds, usually protein in 

 character. Thus built, matter has reached its last high stage of organized 

 existence, and its fall or descent soon begins. In the daily waste of the 

 body or upon the withdrawal of life, this highly endowed organic matter 

 is broken down into inorganic compounds, to begin again the eternal 

 round of Nature. 



II. DIGESTION 



To understand the value of various feeds for stock and appreciate the 

 functions which they serve in the animal body, we must have clearly in 

 mind the processes thru which the food taken into the body is so changed 

 that it can be finally used for the various life functions. 



32. Digestion. The changes which food undergoes within the digestive 

 tract of the animal to prepare it for absorption and ultimate use in build- 

 ing new tissues, repairing body waste, and as a source of energy are 

 collectively known as digestion. Digestion is effected by enzymes, or 

 ferments, produced by glands of the mouth, stomach, pancreas, and 

 small intestine, and by the bile, secreted in the liver. Bacteria inhabit- 

 ing certain parts of the digestive tract attack the woody cellulose of the 

 food, breaking it down and thereby freeing nutrients. In addition to 

 the action of the secretions and bacteria, the food in its course thru the 

 digestive tract is subjected to mechanical processes which tend to reduce 

 it to a fine state of division, the object of the whole process being to 

 separate from the useless matter those constituents which are to nourish 

 the body. 



33. Nutrients. In discussing stock feeding, it is necessary to under- 

 stand clearly what is meant by each of the following terms : 



The term nutrient is applied to any food constituent, or group of food 

 constituents, of the same general chemical composition, that may aid 

 in the support of animal life. Crude protein, the carbohydrates, and fat 

 constitute the generally recognized primary classes of nutrients, altho 

 air, water, mineral matter and vitamines might likewise be so termed. 



The term digestible nutrient covers that portion of each nutrient which 

 is digested and taken into the body. (69) 



34. Concerning rations. On the farm a ration is the feed allowed for 

 a given animal during a day of 24 hours, whether all is fed at one time 

 or in portions at different times. 



A 'balanced ration is the feed or combination of feeds furnishing the 

 several nutrients crude protein, carbohydrates, and fat in such pro- 

 portion and amount as will properly nourish a given animal for 24 hours. 



A maintenance ration is one that furnishes enough, but no more, of 

 each of the several nutrients than is required to support an animal 



