CALCULATION OF RATIONS 75 
Ration Expressed in Protein and Energy Values 
Digestible Energy 
true protein, values, 
pounds | therms 
20 pounds-timothy hay Al 6.71 
4 pounds bran....... Al 1.93 
3 pounds corn meal. . 20 2.67 
2 pounds oil meal...) ‘ = .55 1.58 
WO tall cca sictecsce-fscn' 1,57 12.89 
Variation from standard .07 .89 
The agreement between the standard and the composition of the 
calculated ration is as close as can be desired in this case. No 
importance can be attached to the slight excess of 0.07 pound in the 
digestible protein in the ration or the excess of energy value, 0.89 
therm, and we conclude, therefore, that a ration like the one given is 
theoretically sound, and it will be found practical and efficient in 
feeding dairy cows producing a medium amount of milk, say 20 
pounds a day. 
Comparison of Standards.—The Wolff-Lehmann and Armsby 
standards are recommended for use in calculating rations by differ- 
ent authorities, and both will be found valuable for this purpose. _ 
Either set. of standards has the advantage over the other in certain 
points, and students should become familiar with both, so as to be 
able to apply in each case the particular method of calculation that 
may best serve the purpose in view. We have seen that the Armsby 
standards are, in the main, derived from the investigational work 
done during the last quarter of a century by German scientists, 
largely Kellner, who worked mainly with mature fattening steers. 
Only a small amount of research work relative to the application 
of the system of energy values to the feeding of other farm animals 
has been done; in case of some animals, like sheep, pigs, and poultry, 
such work is entirely lacking (p. 51), so that the standards based on 
energy values, proposed for all animals except fattening cattle, rest 
on a more or less insecure basis. : 
The Wolff-Lehmann standards, on the other hand, do not take 
cognizance of the varying value of digestible matter in different 
feeding stuffs due to the losses of energy in the processes of digestion 
and assimilation. Rations comrposed of feeds that supply similar 
amounts of digestible matter might, therefore, differ greatly in the 
amounts of net available energy that they supply, and would in that 
case have a different feeding value for maintenance or productive 
