258 Basal Metabolism of Swine 



1,000 lb. steer. Now 14 lbs. of average meadow hay supplies about 

 11,500 calories of mctabolisable energy and about 6,000 calories of 

 net energy. Armsby and Fries contend that only the 6,000 calories of 

 net energy are of service to the animal, the remaining 5,500 calories 

 being wasted. Many European writers, amongst them one of the authors 

 (T. B. W.), have assumed that under certain conditions the whole 

 11,500 calories may be of service to the steer, the 6,000 calories of net 

 energy sufficing for physiological purposes, which presumably will not 

 vary greatly witli changes of temperature, and the balance of 5,500 

 calories .saving the oxidation of further material to meet the increa.sed 

 energy required to maintain body temperature in unusually cold 

 surroundings. It is significant to note that whilst Armsby's measure- 

 ments were made in general in a calorimeter at about 65° F. or summer 

 temperature, most European experiments on the maintenance of steers 

 have been made in uiiheated stalls or sheds at winter temperatures of 

 between 40° F. and 50° F. Such a difference in temperature, amounting 

 to from 8 to 14" C. may possibly account for the difference of opinion 

 between American and European investigators. It was with the hope 

 of throwing some light on this point that the writers undertook the 

 investigation described in the following pages. Unfortunately their 

 calorimeter was not large enough to allow of experiments with a 1,000 lb. 

 steer. The experiments were therefore carried out on a hog. 



The investigation also deals with another point. Previous investiga- 

 tions on the effect of temperature on metabolism have shown that at 

 ordinary temperatures an animal maintains its body temperature 

 approximately constant by the rearrangement of its blood circulation. 

 When the air temperature is low, the blood is deflecttid from the skin to 

 the internal organs: the skin gets cold and loses less heat, but the internal 

 temperature is maintained. When the air temperature is high much 

 blood is sent through the skin where it loses much heat and cools the 

 internal organs. 



This method of regulation is however insufficient to maintain a con- 

 stant body temperature when the air temperature falls below a certain 

 point which has been called the critical temperature. Below this point, 

 a fall in the air temperature necessitates the oxidation of further 

 material. The basal metabolism will therefore attain a minimum at the 

 so-called critical point. Below this point it will increase by the heat 

 value of the extra material oxidised. 



