474 
Journal of Agricultural Research 
Vol. XXXI, No. 5 
The metabolizable-energy value of the grain is obtained by a cal¬ 
culation by difference from the hay and grain rations. The metab¬ 
olizable-energy equivalent of the hay in the mixed ration is first 
computed by multiplying the average metabolizable-energy value of 
the hay, previously determined from the hay rations, bv the dry 
matter of the hay of the mixed ration. This is subtracted from the 
total metabolizable energy of the ration. The remainder is the 
metabolizable energy of the grain. Dividing this by kilograms of 
dry matter of the grain gives the metabolizable-energy value of the 
grain per kilogram of dry matter. These values for the grain mixture 
are 2,975 Calories and 3,026 Calories per kilogram of dry matter in 
? eriods 1 and 2, respectively. The average of these—namely, 3,001 
lalories—is the average metabolizable-energy value of the grain. 
COMPUTATION OF THE NET-ENERGY VALUES OF THE HAY AND OF THE GRAIN 
This computation consists of a simple subtraction of the average 
Keat-increment value from the average metabolizable-energy value 
previously determined. The result is the average net-energy value 
of the feed. The average net-energy value of the timothy hay thus 
computed would therefore be 1,190 (2,087 — 897) Calories per kilogram 
of dry matter. The average net-energy value of the grain mixture 
would be 1,682 (3,001 — 1,319) Calories per kilogram of dry matter. 
By dividing the average-net energy value per kilogram of dry 
matter of the feed by its average metabolizable-energy value per 
kilogram of dry matter, the average percentage utilization of the 
metabolizable energy may be obtained. According to this compu¬ 
tation, the utilization of the metabolizable energy of tne timothy 
hay would be 57.02 per cent (1,190-^2,087) and of the grain mixture 
56.05 per cent (1,681 — 3,001). 
The New Method 
The new method involves the separate determination (1) of the 
net energy required for maintenance, (2) of the gain of energy by the 
animal, and (3) of the heat-increment value of the feed. 
The heat production of an animal on feed represents a composite 
of the net energy required for maintenance, in the broad sense; that is, 
including voluntary muscular activities, and of the energy expendi¬ 
ture, or heat increment, due to the consumption of the feed. By 
means of the respiration calorimeter, the total heat production is 
directly measured. The heat-increment value of the feed is deter¬ 
mined by a comparison of periods in which different amounts of 
feed are eaten, as described in the current method, and illustrated in 
Tables III and IY. This computation assumes that the net energy 
required for maintenance is the same in the periods which are com¬ 
pared, and that this assumed, although undetermined, maintenance 
value is canceled in subtracting the heat production of one period 
from that of another. To illustrate this, if H and H 1 represent, 
respectively, the heat production of two periods, h and h lt the heat 
increment due to the feed, and m the net energy required by the 
animal for maintenance in either period, then H=m + h, and 
H 1 = m+h v Subtracting the second expression from the first results 
in the equation H— H t — h — h v 
