ANIMAL NUTRITION 183 



needed; and that, if these are insufficient, the protein com- 

 pounds' may be drawn upon as a source of energy. This 

 latter source makes the cost of the energy greater, and it 

 also imposes extra work on the urinary system, through 

 which the nitrogenous products of the oxidation of protein 

 are removed. During work, the quantity of carbon dioxide 

 exhaled is much increased, due to the greater quantity of 

 carbonaceous matter that is oxidized. The latest investi- 

 gations show that no more nitrogenous tissue is broken 

 down by animals while at work than at rest. Working 

 animals thus require a more concentrated feed and less 

 roughage. 



The horse requires considerably less dry matter per 1000 

 pounds of live-weight than do the ruminants, and its food 

 should be rich and easily digested. Horses must be fed in 

 accordance with the work that they are doing, the ration 

 being reduced when at rest or light work, to secure economical 

 results. It is advisable to give most of the roughage at 

 night. A moderate but not an excessive amount of hay is 

 desirable. The Wolff-Lehmann standards recommend a 

 nutritive ratio of 1 to 6.2 for a horse on medium work, and 

 Henry states that " from 10 to 18 pounds of concentrates 

 should be fed, according to the severity of the labor, the 

 total grain and hay averaging not less than 2 pounds per 

 hundred pounds weight of the animal." 



