to be paid for by increased muscular activity and correspondingly 

 increased consumption of food for maintenance. 



Condition. 



The condition of an animal as the word is commonly used is 

 practically synonymous with the amount of fat tissue carried. Kell- 

 ner, in addition to the experiments already mentioned, investigated 

 the maintenance requirement of three fat animals, including one 

 (Ox B) of those whose requirements in the thin state were deter- 

 mined. His results were somewhat contradictory. Ox B showed 

 a lower requirement per thousand pounds live weight when fat than 

 when thin, but the average for three fat animals was materially 

 higher than that for thin animals, namely 8.85 Therms available 

 energy per thousand pounds live weight. Evvard's live weight 

 experiments also included a second sixty-day trial upon the same 

 three animals partially fattened which showed a maintenance re- 

 quirement of 9.07 Therms as compared with 7.18 Therms in the 

 thin state. 



External temperature. 



As the experiment cited on page 8 illustrates, the consump- 

 tion of feed is a source of heat to the animal and this heat aids in 

 maintaining the normal body temperature. It has been clearly 

 shown that at temperatures in the neighborhood of 6oF. a steer on 

 a maintenance ration is producing considerably more heat than is 

 necessary to maintain his body temperature. If the surrounding 

 temperature falls, it is evident that for a time no increased heat 

 production would be necessary, but sooner or later a point would 

 be reached below which increased oxidation of feed or tissue would 

 be required for the sake of additional heat production, although 

 just what this temperature is has not been determined. 



With animals consuming a heavy ration, fattening steers 

 for example, the food consumption is the source of a large amount 

 of heat and it has been clearly demonstrated that such animals may 

 be exposed to a very considerable degree of cold without leading 

 to the consumption of any additional material for the sake of heat 

 production alone. In such cases, therefore, the maintenance require- 

 ment would not be increased until a much lower temperature was 

 reached than in the case of the animal on a simple maintenance 

 ration. 



(20) 





