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 



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: 



