330 MANAGEMENT AND BREEDING OF HORSES 



the amount of food required to support life, such as main- 

 taining body temperature, repairing waste tissue, pro- 

 viding for the muscular activity of vital processes, and 

 the like. The demands on the body for maintenance are 

 for the production of muscular energy and heat; there- 

 fore, the maintenance ration may consist largely of car- 

 bohydrate material. This is an important observation 

 in the v/intering of idle horses. 



Productive rations. — After the body needs have been 

 supplied, the food that goes to the production of some 

 useful product, as labor in the case of the horse, is called 

 a productive ration. It is the food consumed in excess 

 of the amount required for maintenance that enables the 

 animal to produce a useful product. A productive ration, 

 therefore, may be looked upon as consisting of two parts, 

 the food of maintenance plus the food of production. In 

 forming a productive ration, we should give the animal all 

 of the food he will consume and make sufficient returns 

 for in production. This requires careful consideration, 

 as the amount of production is not always in proportion 

 to the food consumed in excess of that required for main- 

 tenance. In this respect the individuality of the animal 

 plays an important part; thus we have horses that are 

 hard keepers or easy keepers, as the case may be. This 

 variation among individual horses is so great that feed- 

 ing standards can be used only as mere guides. 



Feeding standards. — Many experiments have been 

 conducted to determine the relation between the amount 

 of muscular work performed and the food required per 

 day. As a result of such work we have two classes of 

 standards for the work horse, the Wolff-Lehmann, based 

 upon the digestible nutrients, and the Kellner or 

 Armsby, based upon the energy. Before we can use the 

 former it is necessary to know the digestible nutrients 

 in the food (p. 448), and before we can use the latter it is 

 necessary to know the energy value of the food (p. 447). 



