CALCULATION OF RATIONS 



Ration Expressed in Protein and Energy Values 



75 



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 composed 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 



