MILK PRODUCTION AND BODY INCREASE OF DAIRY COWS 29 
periods I and III, the following recomputation will give utilization 
and net energy values for this period which are probably more nearly 
correct. 
The milk on the calorimeter day was 1.19 kilogram = 1,147.9 Calo- 
ries, a difference of 363.8 Calories from the average. This difference 
in milk production, based on period I, would be 363.8 -f- 0.6483 = 561.2 
Calories (usual method) or 363.8-^0.8105 = 448.9 Calories (improved 
method) of available metabolizable energy. 
But these values represent the reduction in body gain which, based 
on the percentages obtained in period III, would be by the usual 
method equal to 561.2x0.49815 = 279.6 Calories of bodv gain. 
In period II the gain was 3,663.2 Calories, and 3,663.2-279.6 = 
3,383.6 Calories corrected gain. Applying the percentage utiliza- 
tion previously computed we have 3,383.6-^0.49815 = 6,792.3 Calo- 
ries (usual method), or 3,383.6^0.60961 = 5,550.4 Calories (im- 
proved method) of available metabolizable energy which, deducted 
from the total available, leaves for milk production the following: 
8, 155. 6 6, 572. 8 
6, 792. 3 5, 550. 4 
1, 363. 3 Calories. 1, 022. 4 Calories. 
The corresponding percentage utilization would then be: 
— — | ' o o — =84. 20 per cent utilization (usual method) . 
— — .. 'p.^ T — = 112. 27 per cent utilization (improved method). 
The net energy for milk production can be computed as follows: 
8, 935. 2 : 8, 935. 2 + 6, 792. 3 : 3. 759 : X. X = 6, 616. 4. 
7,190.1-6,616.4 = 573.7 grams dry matter and 1,147.9 Calories -^-0. 5737 = 
2. 000 Therms net energy per kilogram feed. 
All these results suggest that the computed maintenance ration , 
at least for cow 631, period III, was too low. It had been computed 
in consideration of the increase in live weight of the animal; but 
since this increase must have been due largely to the development 
of the fetus, it seems possible that the increased weight on this 
account would represent more protoplasmic activity than the same 
increase of body weight apart from the fetus, the maintenance 
requirement, therefore, being greater. This may be true not only 
for period III but also for period II. In the light of other results, 
and the above hypothesis, it would appear that the maintenance 
requirement as computed for period III is about 2 per cent too low. 
If an allowance of 2 per cent increase in maintenance for period III 
is made, and the new values for body gain determined, the percentage 
utilization of the available metabolizable energy for milk production, 
with cow 631, period II, would be, computing as before, 74.91 per 
cent, or 98.92 per cent utilization (usual and improved methods, 
respectively), and the net energy for milk production 1.78 Therms 
per kilogram of dry matter of the ration. 
Thus it is seen that a change of 2 per cent in the values for main- 
tenance will make the values applying to cow 631, period II, cor- 
respond to the other milking periods. The data as to cow 631, 
period II, therefore, constitute in reality a fair proof of the accuracy 
of the experiment as a whole, and also an indication that the main- 
tenance requirement of an animal in the later stage of gestation may 
