1076 
Journal of Agricultural Research 
Vol. XXXI, No. 11 
The data obtained in the experimental work with cow 885 have 
been included in Table XX, notwithstanding their obvious unre¬ 
liability. It is plainly evident that the heat production of this cow 
is not truly related to the feed of the period, and has been rendered 
valueless for present purposes by the refusal of feed while on experi¬ 
ment. As specific evidence on this point, attention is directed to 
experiment 221D-885-II-III. The computed heat production in 
the maintenance period (III), Table XVII, is greater than in the 
supermaintenance period (II), an absurd finding under the condi¬ 
tions of feed intake and environmental temperature of the experiment. 
Referring to Table XX, omitting the data obtained with cow 885, 
the average heat increment per kilogram of dry matter of the ration 
is 1,053.1 Calories. 
THE COMPUTED FASTING KATABOLISM AS A MEASURE OF THE 
MAINTENANCE REQUIREMENT 
It must be kept clearly in mind that the term fasting katabolism 
is not synonymous with basal katabolism, which latter involves the 
element of complete muscular repose. The term “ fasting kata¬ 
bolism,as usea in this paper, represents the minimum energy re¬ 
quirement incident to the normal daily activity of the animal, and 
might more accurately be termed the “ 24-hour normal fasting katab¬ 
olism.” It will also be noted that in computing the maintenance 
requirement to a 12-hour-standing basis, this view has been modified 
to some extent, for it is impossible to compare the maintenance 
requirements of two animals one of which, for instance, normally 
stands three-fourths of the time and the other one-half of the time 
without neutralizing the effect of this variant. 
The importance of the 24-hour normal fasting katabolism in rela¬ 
tion to feeding practice is obvious. While it is not as nearly constant 
as the theoretical true basal katabolism, its use is rendered imperative 
in experiments involving animals the muscular movements of which 
can not be perfectly controlled. 
The foregoing data provide a basis for computing the maintenance 
requirement of the individual animal. The relatively constant total 
katabolism of a fasting animal (above the point of critical thermal 
environment) is a measure of the energy required for vital activities, 
and is consequently the minimum amount required for maintenance. 
Since it has been considered impracticable heretofore to measure the 
normal fasting katabolism of cattle directly by complete fasting 
experiments, the result sought has been attained indirectly from 
experiments in which the subjects received certain amounts of feed, 
as expressed in Table XXI. 
