THE BALANCE OF NUTRITION 197 



such, for example, as the relative values of the carbohydrates 

 and fats, the changes of live weight are of little value as indica- 

 tors. For this there are two principal reasons. 



282. Fluctuations in live weight. In the first place the 

 live weight of an animal fluctuates considerably from day to day, 

 even when taken under what seem to be identical conditions, 

 chiefly on account of variations in the weight of the contents 

 of the digestive tract. This is true of all animals, but especially 

 of herbivora on account of their comparatively bulky feed, and 

 reaches the extreme in ruminants. 



For example, a steer which had been receiving daily for two 

 months a uniform ration of 6.35 Kgs. of timothy hay and which was 

 kept under as uniform conditions as possible was weighed daily 24 

 hours after watering. On February 19 he weighed 419.0 Kgs. and 

 on March 6 practically the same amount, 418.6 Kgs. The inter- 

 mediate weights, however, were as follows: 



February 19 419.0 Kgs. 



February 20 43 1 .6 Kgs. 



February 21 43i-o Kgs. 



February 22 440.6 Kgs. 



February 23 431.2 Kgs. 



February 24 444-8 Kgs. 



February 25 427.6 Kgs. 



February 26 427.9 Kgs. 



February 27 437.8 Kgs. 



February 28 436.0 Kgs. 



March i 437-2 Kgs. 



March 2 443-Q Kgs. 



March 3 428.4 Kgs. 



March 4 433.4 Kgs. 



March 5 436.8 Kgs. 



March 6 418.6 Kgs. 



It is evident that conclusions based upon a comparison of single 

 weighings would have been entirely untrustworthy. Thus a com- 

 parison of the live weight of February 19 with that of March 6 would 

 have led to the conclusion that the animal was being practically main- 

 tained. If, however, the initial weight had chanced to be taken on 

 February 20, a comparison with that of March 6 would have shown 

 a loss of 13 Kgs., while on the other hand, a comparison of February 

 19 with March 5 would have shown a gain of 17.8 Kgs. Even aver- 



