92 FEEDS AND FEEDING, ABRIDGED 



This ration closely approaches the standard. It falls below by more 

 than 1 lb. of dry matter, but this deficiency is unimportant. The 

 Wolff-Lehmann standards were devised to cover the common systems 

 of feeding in Europe, where some straw or other low grade 'roughage is 

 commonly included in rations for horses and ruminants. When only 

 such high grade roughages as silage and legume hay are used, rations 

 which supply enough digestible nutrients will fall below the standard 

 in dry matter. If the ration furnishes sufficient bulk to distend the 

 digestive tract properly, no further attention need be paid to such a 

 deficit. The excess of fat in this case will more than make up the 

 trifling deficit of carbohydrates, for fat has 2.25 times the heat value of 

 carbohydrates. The nutritive ratio of this ration is 1 :12.1, which is 

 close to the standard. American rations will usually furnish an excess 

 of fat over the standard, in which case the carbohydrates may fall 

 somewhat below, as an offset. 



III. The Aemsby Net Energy Values and Feeding Standards 



In Chapter III it has been pointed out that the total quantity of 

 digestible nutrients in a feeding stuff is not theoretically the true 

 measure of its feeding value, as is assumed in the Wolff-Lehmann 

 feeding standards. Experiments by Kellner and Zuntz in Germany 

 and by Armsby in this country have shown that to find the true net 

 value of a feed for production it is necessary to deduct from the total 

 energy furnished by the digestible nutrients in the feed, the energy 

 lost in the urine and the gases produced in the digestive tract and that 

 spent in the work of mastication, digestion, and assimilation. 



Net energy values. — Kellner was the first to prepare tables showing 

 the net energy values of feeding stuffs. In these he took 1 lb. of 

 digestible starch as his unit and expressed the net energy values of 

 different feeds in terms of "starch values." He then drew up feeding 

 standards based on these starch values, which are now quite largely 

 used in Germany. 1 We will not discuss these in detail, but will con- 

 sider instead Armsby 's net energy values and feeding standards, which 

 are chiefly used in this country by those desiring to compute rations 

 according to the net energy system. 



Based chiefly on Kellner 's studies, Armsby has drawn up a table 

 showing the net energy values of some of the leading American feeds, 

 expressed in therms, and also giving the total amount of dry matter 

 and the amount of digestible true protein (not digestible crude protein) 



i For Kellner's starch values and feeding standards see his books, Erniihrung 

 der Land. Nutztiefe and Futterungslehre, and the English translation of the 

 latter book, The Scientific Feeding of Animals. 



