MAINTENANCE THE ENERGY REQUIREMENTS 305 



Like the temperament, any external conditions tending to 

 affect the degree of muscular activity will also tend to affect 

 the maintenance requirement. The steer confined in a stall, 

 for example, may take less muscular exercise, and therefore 

 require less energy for maintenance, than one simply confined 

 to a pen or open yard. The animal comfortably bedded and 

 thereby induced to spend much of his time lying down will 

 consume a smaller proportion of his feed for maintenance than 

 one kept under less comfortable conditions. Any sort of 

 excitement is likely to be paid for by increased muscular ac- 

 tivity and correspondingly increased consumption of feed for 

 maintenance. 



392. The plane of nutrition. It is somewhat generally be- 

 lieved that the amount of feed necessary for maintenance varies 

 with the plane of nutrition on which the animal is kept. By 

 this is meant that an animal which has been highly fed for 

 some time will require a larger amount of feed for maintenance 

 than a similar animal which has been sparsely fed and is in 

 a more or less reduced condition. Thus, Waters 1 writes : 

 " Apparently the animal organism when kept for a long 

 period of time on a low nutritive plane, as in the case of main- 

 tenance animals, gets on a more economical basis than when 

 more liberally fed. For example, if we reduce the feed of an 

 animal that has been previously liberally nourished to a point 

 where for a month or more there is a small loss in weight, an 

 equilibrium will later be established and subsequently the 

 animal may increase in weight, the quantity and quality of 

 the feed remaining the same. Thus a ration that was insuf- 

 ficient to sustain live weight at first may be capable later of 

 maintaining the animal at a stationary body weight, and still 

 later of causing an increase in weight. Digestion experiments 

 with a number of animals indicate that a part of this is due to 

 the more complete digestion of the feed by the animal on a low 

 nutritive plane, but so far as the experiments have thus far pro- 

 gressed there does not seem to have been a sufficient increase 

 in the degree to which the feed has been digested to account 

 for all the increased efficiency in the ration noted." 2 



Comparatively little experimental confirmation of these re- 

 sults has as yet been published, although respiration experi- 



1 Proc. Soc. Prom. Agr. Sci., 1908, p. 96. 2 Compare Chapter XVI, 3 (722). 

 X 



