178 THE CHEMISTRY OF THE FARM 



far greater in the case of an animal than in the case 

 of a steam engine. 



"When labour is demanded from an under-fed animal 

 the oxidation taking place may be in excess of the 

 food supplied ; in such a case the fat and albuminoids 

 of the animal tissues are oxidised, and the excretion of 

 urea becomes increased. A working animal ill sup- 

 plied with food will thus suffer seriously in condition. 



When an animal " out of training " is suddenly 

 called upon to perform hard work it will at first show 

 an increased oxidation of albuminoids as the result of 

 labour ; but this will cease as the body becomes fit for 

 work, if sufficient food is supplied. During training 

 for increased work an albuminous diet will be neces- 

 sary, as the muscular apparatus has to be built up. 



Maintenance Diets. — In the case of an adult animal 

 not increasing in weight, and performing a minimum 

 amount of work — as, for instance, a horse or ox in a 

 stable — the quantity of food required to maintain the 

 condition of the animal is reduced to its smallest 

 limits. The minimum quantity of food required by 

 an animal is most accurately found by ascertaining 

 the various gains and losses of energy taking place 

 with a known but barely sufficient diet ; the balance 

 of energy dissipated as heat, after allowance has been 

 made for all gains and losses in the animal, is an exact 

 measure of the minimum requirements of the body. 

 Kellner has made numerous experiments of this kind 

 with lean, full-grown oxen, kept in a stable at a tem- 

 perature of about 60° Fahr., and receiving diets varying 

 in quality and quantity. The total food required varies 

 with the size of the ox ; but, as we have already seen 

 (p. 174), in proportion to its surface, and not according 



