ENERGY VALUES OF RATIONS FOR FARM ANIMALS, 29 
THE CHOICE OF FEEDING STUFFS. 
When, as in the last example, feeding stuffs must be purchased in 
order to get the desired relation between the proteim and the energy 
of the ration, it is evident that often a wide range of choice may be 
offered. In such a case the question at once arises which of the vari- 
ous feeds available is it most economical to purchase, it being evident 
of course, that this is not necessarily the one offered at the lowest price. 
No simple method of determining this point is possible, because, 
as we have seen, the feed serves two entirely distinct purposes in the 
body. Sometimes the supply of protem is the specially important 
point, and in other cases what is needed is a supply of energy without 
- special reference to whether its source be protem or nonnitrogenous 
material. Consequently, the relative values of two feeding stuffs may 
vary under different circumstances. Some writers have based their 
comparisons of the values of by-product feeds solely upon their con- 
tent of protein, for the reason that such feeds are often bought espe- 
cially to supply this ingredient, while the fats and especially the car- 
bohydrates are usually produced in abundance upon the farm. They 
regard that purchased feeding stuff as the most economical which fur- 
nishes a pound of digestible protein at the lowest cost, ignoring any 
value in the other ingredients. It is obvious, however, that this is a 
one-sided view. The other ingredients have a value, and this is espe- 
cially true in the case of a feeder who buys a considerable part of his 
erain supply and depends upon it as a source of energy as well as of 
protem. The method of comparison illustrated in the following pages 
is based primarily upon the cost per unit of energy because this is on 
the whole the most important function of the feed, but the method 
takes account also of the amount of protein present. 
Let us suppose the following feeding stuffs are available to a dairy- 
man at the prices named: 
Prices of feeds per ton. 
Orrsaoscemtsiper, bushel) s. 222.02... 5) 32e See es oo ee $25 
ABrotempninet epee eae oe tet ee Se et ie 25 
“HVS INE (OTERIT ais 2.8 = AON ey a a Se a aaa ASE pag remae Oe 21 
eenimmanc clams, COUR). 6 Saco MO ye. tS ee Mes oe Maia each ge 24 
Dried brewers’ grains........---- nda Da AN eedcce SS rege Neg 23 
Gilituer, 11M lark 5 Bea ea Nei aa ea a Nae ra ge Dik 
Cononuscedtmenk (prime)! de 05 00. OL EE ese ee ee eee 30 
Old-process linseed meal......-.-.-.-- SE ariel tte Nee ee ee Pa de 33 
The supply of coarse feed on the farm is sufficient to furnish each 
animal per day 32 pounds of silage and 8 pounds of clover hay; the 
cows average 1,000 pounds each and may be expected to produce per 
day about 24 pounds of milk testing 4.5 per cent fat. 
