ENERGY VALUES OF RATIONS FOR FARM ANIMALS.. 19 
mals—such, for example, as the 2 to 3-year-old steers which are com- 
monly fattened in the corn belt—probably 3.25 therms of net energy 
per pound of gain in live weight is a fair allowance, although more 
appears to be often used in practice. As yet no corresponding data are 
available for the fattening of growing animals, as, for example, in the 
production of the so-called baby beef. It is not probable, however, 
that any larger amount of protein is required in such fattening than 
in feeding simply for normal growth, so that the additional feed 
given for fattening may, from this point of view, consist largely of 
nonnitrogenous material; that is, carbohydrates and fats. Itis to be 
noted, however, that an excess of these materials in the ration tends 
to cause less perfect digestion and also that a moderate proportion 
of the more nitrogenous concentrates seems to promote the con- 
sumption of heavy rations. Kellner recommends that at least 1 
pound of digestible protein be supplied in the ration for each 8 to 10 © 
_ pounds of carbohydrates and fat. 
REQUIREMENTS FOR MILK PRODUCTION. 
Of all forms of animal production that of milk is perhaps the most 
variable and most influenced in its amount by the feed supply. The 
energy relations of milk production have not been very fully investi- 
gated. Tentatively, however, it seems safe to estimate that the pro- 
duction of 1 pound of average milk, containing about 13 per cent of 
total solids and 4 per cent of fat, will require approximately 0.27 therm 
of net energy value in the feed. Naturally this amount would vary 
with the quality of the milk, milk rich in fat and in total solids requir- 
ing more than milk contaming more water or a lower percentage 
of fat. 
The matter of the protein requirements for milk production has 
not been altogether cleared up. It seems to have been pretty well 
demonstrated that, for a time at least, a moderate milk production 
may be kept up on a supply of protein only slightly exceeding that 
found in the milk produced (of course, in addition to the maintenance 
requirement). In the case of average milk, this would call for about 
0.032 pound of digestible protein for each pound of milk. It has not 
been demonstrated, however, that a cow can keep this up indefinitely. 
Furthermore, for the production of liberal yields of milk more protein 
seems to be required, or at least to be advantageous. 
Tentatively, the requirements of digestible true protein and of 
net energy for the production of 1 pound of milk may be formulated 
as follows. 
