74 PRINCIPLES OF FEEDING FARM ANIMALS 
A ration containing a relatively small amount of protein is 
spoken of as having a wide ratio, e.g., 1:7 or higher, and one with a 
relatively high protein content as having a narrow nutritive ratio, 
e.g., 1: 5.4 or less. A medium ratio would lie between these limits. 
The nutritive ratios of different feeding stuffs range from 1:1 or 
below, as in the cases of dried blood, tankage, cotton-seed meal, to 
1: 20 or above, as in the case of cornstalks, sorghum hay, and straw 
of the cereals. The former feeds and others in the same class are 
known as protein feeds or nitrogenous feeds, and the latter as starchy 
or non-nitrogenous feeds. The nutritive ratio of a feed is of value 
in showing whether it supplies largely protein or non-nitrogenous 
components and whether one feed can be substituted for another 
without change in physiological effect (see p. 38). 
Armsby’s Energy Values.—As previously stated, the Armsby 
standards show the amount of digestible true protein and energy 
values required for feeding different classes of farm animals. The 
requirements for maintenance and for production are given sepa- 
rately. For a dairy cow the standard thus calls for the following 
amount of nutrients for the two purposes: 
For maintenance, 0.5 pound digestible true protein and 6.0 
therms of energy values per 1000 pounds live weight. _ 
For production, 0.05 pound digestible true protein and 0.3 
therm per pound of milk of average quality. 
In the example given above the amount of nutrients to be fur- 
nished the cow would, therefore, be as follows, assuming the cow 
to weigh 1000 pounds: 
Nutrients in Energy Values 
Digestible Energy 
true protein values, 
pounds therms 
For maintenance. .... 5 6.0 
, For production....... * 1.0 6.0 
Total requirements 15, 12.0 
By reference to Table III in the Appendix it will be found that 
the feeds given in the preceding example contain the following 
amounts of digestible protein and energy values: 
