MILK PRODUCTION AND BODY INCREASE OF DAIRY COWS 27 
the two sets of met aboliz able calories available, the total meta- 
bolizable energy available for milk production is obtained. 
8,740.0 usual method. 6,999.2 improved method. 
444.4 363.2 
Difference, 8,295.6 Calories. 6,636.0 Calories. 
These two values represent the amount of metabolizable energy 
available for milk production. Dividing the milk yield by these 
values the following figures are obtained : 
1 ooQg a — =64.832 per cent utilization (usual method), 
or 
— — „»' n — =81.046 per cent utilization (improved method). 
oooo.O 
To obtain the net energy value of the feed for milk production it is 
necessary first to correct the maintenance requirement so as to 
include the body gain and then subtract this amount from the total 
feed eaten. Thus, in period I, cow 631, the maintenance requirement 
including the body gain will be, using the old method, according to 
the proportion; maintenance metabolizable : maintenance metaboliza- 
ble +221.4 ^49.815 :: weight of maintenance ration :X. X =dry 
matter of feed. 
Thus 8,609.9 : 9054.3 : : 3577 : X. X = 3,761.8 grams of feed. 
Total ration 7,208.4 — 3,761.8 = 3,446.6 grams of feed mixture for production of 
milk. 
Dividing the milk calories by this amount the net energy of the 
feed for milk production per kilogram dry matter of the feed is 
obtained. 
Thus 5378.2-^3.4466=1.5604 therms of net energy for milk production. 
For body increase 1.2121 Therms .of net energy. 
For milk production 1.5604 
Difference 0.3483 = 22.32 per cent. 
In this connection it is of interest to note that Hansson (8) from a 
very large number of long-time practical group experiments with 
milking cows has obtained for the individual grain barley, which is 
the standard for the feed-unit system, a net energy value for body 
increase equal to 1.650 Therms per kilogram of grain containing 
14.5 per cent moisture, and for milk production a net energy value of 
2.100 Therms, a difference of 21.5 per cent. 
This shows a remarkably close agreement for the percentage 
difference between net energy for body increase and net energy for 
milk production, as found by different experimenters, especially when 
the extremely different methods of experimentation by means of which 
the results were obtained are considered. 
It must be borne in mind, however, that in these experiments the 
maintenance requirement was computed from published averages 
and not determined for the cow referred to above. 
Having thus determined the net energy value of the feed for body 
gain from the dry period of the one cow, by applying this value to 
the other cows, the percentage utilization of the metabolizable 
energy available for milk production may be computed in the manner 
previously described. The results of such computations are recorded 
in Table 24. 
