66 



MAINTENANCE RATIONS OF FARM ANIMALS. 



relative maintenance requirements of two animals even though their 

 minimum physiological requirements may be identical. In experi- 

 ments of any considerable duration on normal animals, it is impossible 

 to avoid more or less expenditure of energy in this incidental muscular 

 work, while it is often a matter of difficulty to make the different 

 periods of an experiment comparable in this respect. 



LYING AND STANDING. 



Furthermore, considerable muscular exertion is involved during the 

 waking hours in maintaining the relative position of the different 

 members of the body. This is notably true of the effort of standing. 

 In experiments by Armsby and Fries 1 the heat radiated per 

 minute by a steer while standing was found largely to exceed that 

 given off while lying, the excess in 25 experiments ranging from 28.3 

 to 64.5 per cent, although there were indications that the amount of 

 feed consumed was also a factor. 



On the other hand Dahm, 2 working in Zuntz's laboratory and by 

 his methods, found an increase of only 8 per cent in the respiratory 

 excretion of C0 2 by a young bull when standing as compared with 

 that when lying, but Zuntz 3 himself in earlier experiments on a dog 

 observed differences similar to those found by Armsby and Fries for 

 cattle, the average oxygen consumption per minute being while lying 

 174.3 c. c. and while standing 245. G c. c, or an increase of 41 per cent. 

 Benedict 4 observed an increase of from 13.3 to 18.8 per cent, or an 

 average of 16.5 per cent, in the heat production of man when standing 

 as compared with that observed when sitting quietly in a chair. 



It is clear, then, that of two animals, one of which lies down for 12 

 hours and the other for 8 hours out of the 24, the former will, other 

 things being equal, require less energy for maintenance. In the 

 results regarding the maintenance ration thus far reported, with 

 the exception of the Pennsylvania experiments, this factor has not 

 been taken into account. 



INDIVIDUALITY. 



It appears quite probable that those differences between the main- 

 tenance requirements of different animals which are ascribed some- 

 what vaguely to " individuality " are due to a large extent to varying 

 amounts of muscular activity. In general, the nervous, restless 

 animal will have a higher maintenance requirement than the quiet, 

 phlegmatic one. Thus the table on page 40 shows that Armsby and 



1 Bureau of Animal Industry, Bulletins 51, 74, 101, and 128. 



2 Biochemische Zeitschrift, vol. 28, p. 494. 



"Archly fur die gosammte Physiologie des Menschen und der Thiere (Pfliiger), vol. G8, 

 p. 191. 



4 Loc. fit, p. 244. 



