1056 
Journal of Agricultural Research 
Vol. XXXI, No. 11 
body of the animal by 2.020 therms. [The basal ration supplied 5.687 therms of 
metabolizable energy and the losses of body protein and fat were equivalent to 
2.377 therms per day.] Evidently, then, to have reduced it by 2.377 therms, 
2 377 
that is, to zero, would have required the addition of 2. 2.471 kg. of the 
hay, equivalent to 4.207 therms of metabolizable energy. The total mainte¬ 
nance ration of this particular feeding stuff, then, would have been the basal ration 
plus this amount, or 5,670 kg. of the hay, equivalent to 9.894 therms of metabo¬ 
lizable energy. 
It will be noted that the above data are expressed in terms of 
metabolizable energy. So far as the method is concerned it is im¬ 
material whether results are expressed in terms of metabolizable or 
of net energy but, for reasons which are set forth more fully in the 
discussion to follow, net-energy values have been used throughout 
this study. 
As to the variability of the maintenance requirements of farm 
animals, it was expected that one species would differ from another, 
and that one individual would differ from another of the same species,• 
and the writers found it so. Size, weight, temperament, variations 
of body temperature as between individuals and from day to day 
in the same individual, digestive activity, sex, physical condition, 
age, variation in the time spent lying as compared with the time spent 
standing—all these, theoretically at least, have a definite bearing on 
the maintenance requirement. External conditions, such as thermal 
environment, seasonal variation (10, p. 33), the presence of attend¬ 
ants, and annoyance caused by insects, also have bearing, not 
only on the maintenance requirement, but also on the accuracy of 
the determination of it. 
A consideration of these many factors which contribute to the 
maintenance requirement indicates the desirability of directly deter¬ 
mining this requirement of an experimental subject, in research on 
problems of production, rather than applying average figures for 
maintenance. 
In the experiments of this series, the general plan was to deter¬ 
mine the maintenance requirement of each individual and to apply 
these data in the determination of the net-energy values of feeds for 
milk production and for body increase with this same animal. In a 
number of instances the writers were unable to carry out this plan 
and were compelled to make use of average figures. 
A perusal of the details of the experiment shows that the heat 
production and the gaseous excretion were determined on only two 
days, the ninth and tenth, of the experimental periods. It has been 
assumed that these two days are representative of the period. That 
this assumption may introduce an error into the values is undeniable, 
but that it is not seriously disqualifying is shown by the uniformity 
of similar data recorded in the work of Armsby and Fries (1), and 
by the agreement of results from the one experimental day with 
those from the other. 
It will also be noted that these present experiments represent the 
24-hour metabolism with normal activity as to standing and lying, 
and therefore should not be considered as representative of complete 
repose. 
The procedure and the general plan of experimentation have been 
fully outlined in a previous paper (4). 
