U. S. DEPARTMENT OF AGRICULTURE 
followed faithfully during the entire series of experiments extending 
over a period of seven years. 
GENERAL SCHEME FOR EXPERIMENTS WITH RESPIRATION 
CALORIMETER ON MILK PRODUCTION 
Animals to be used. — Since considerable work on cattle has already been done 
with the respiration calorimeter, and since cows constitute the commercial 
source 6f milk, it would be most desirable to experiment with those animals: 
If, however, this is deemed impracticable, because of the difficulty involved in 
the satisfactory collection of the excreta of cows, necessitating the employment 
of watchmen at very considerable expense, it is thought that milk goats will, 
on the whole, be fairly satisfactory as experimental animals, at least for pre- 
liminary investigations. If they are used it is proposed to employ a form of 
metabolism cage devised by Bowes, which permits the separation and collection 
of the feces and urine with comparatively little oversight. 
General -problem. — It is proposed to determine the total energy of the feed con- 
sumed by milking animals, the losses of energy in the excreta, the expenditure 
of energy consequent upon the consumption of feed, and, by difference, the net 
energy of the feed, in the same general manner as in experiments on steers. 
Furthermore, however, it is proposed to determine the distribution of this net 
energy of the feed between the two possible forms of production, viz, fattening, 
or milk secretion, and the effect upon it of the quantity of the feed as well as of 
other factors. 
Lines of experiment. — The following general lines of experimental work are 
outlined : 
1. To determine the maintenance requirement of the dry animal. 
2. Feed a moderate ration and, by means of successive respiration-calorimeter 
experiments, trace the variations in the distribution of net energy between milk 
production and body gain with advancing lactation. In this way, it is hoped 
to determine the quantitative relation between the two forms of production. 
3. Study the effect of varying amounts of the same combination of feeding 
stuffs in increasing the milk production on the one hand and the body gain of 
the animal on the other hand. 
4. Study the effect upon milk production and body gain of substituting protein 
for carbohydrates or vice versa in rations otherwise identical. 
SCHEME FOR EXPERIMENTS WITH DAIRY COWS 
Later Director Armsby prepared the following outline : 
The general problem proposed is to determine in terms of energy the efficiency 
of the cow as a mechanism for converting feeding stuffs into milk. 
The efficiency here considered is what may be called the net efficiency; that is, 
the percentage of the amount of feed energy supplied in excess of that required 
for maintenance which is recovered in the milk. The net efficiency, as thus 
defined, constitutes one of the factors of the economic efficiency, but the latter 
necessarily varies with the proportion of the total feed which is available for 
productive purposes. Otherwise expressed, the problem is to determine the net 
energy values of feeding stuffs for milk production. This problem might be 
attacked in two ways. 
1. By the direct determination of the net energy values of single feeding stuffs 
by substantially the methods used in previous investigations upon beef produc- 
tion. This method, however, would be somewhat tedious and would involve 
more or less correction of the results, upon the basis of average figures, for any 
fattening of the animals which might occur. 
2. By determining upon identical animals the relative availability of the energy 
of one or a few standard feed mixtures for fattening, on the one hand, and for 
milk production on the other, and applying the ratio thus determined to the data 
already available for utilization in fattening. 
The second of these two methods appears to promise more immediate, even if 
somewhat approximate results, and is the method which it is proposed to follow. 
The general plan is to make in a first season two or three respiration-calorim- 
eter experiments upon dry cows receiving different amounts of the standard 
feed mixture by a comparison of which the maintenance requirements and the 
net utilization in fattening by the individual animals may be determined. 
Incidentally the basal katabolism of the animals as computed by a comparison 
of the two periods on different amounts of feed is to be compared with katabolism 
