MEASURING THE USEFULNESS OF FEEDS 43 



When 100 lbs. or 263.1 therms of wheat gluten, which is principally 

 protein, was digested and absorbed into the body, a loss of 49.2 therms 

 occurred in the urine, this loss coming from the breaking down of this 

 protein nutrient within the body, or from the breaking down of body 

 tissue which was replaced by new protein from this source. In all, 

 167.5 out of 263.1 therms in 100 lbs. of gluten were lost either in the 

 urine or in carrying on the work of mastication, digestion, and 

 assimilation, leaving 95.6 therms which might be temporarily or 

 permanently stored in the body. This amount of protein was avail- 

 able for building protein tissues or lean meat, which would be its 

 highest use, or it could serve for the production of body fat, etc. 



Studying the data for the feeding stuffs, we observe that 100 lbs. 

 of corn meal contains 170.9 therms of total energy. Of this, 15.7 

 therms is lost in the undigested matter of the feces. In the methane 

 gas formed in the fermentations in the paunch there was a loss of 

 15.9 therms. A further loss of 6.6 therms occurred in the urine. 

 Adding these losses together and subtracting the sum from the total 

 energy value, 170.9 therms, we find that 132.7 therms remained. 

 This is the amount of available energy in 100 lbs. of corn meal. 

 Further losses of energy, amounting to 62.0 therms, take place thru 

 the production processes ; i. e., masticating the corn, digesting it and 

 assimilating the digested nutrients. This brings the total loss to 

 100.2 therms, leaving 70.7 therms as the net energy value of the 

 100 lbs. of corn meal. The same weight of timothy hay furnishes 

 but 26.4 therms of net energy and of wheat straw but 10.3 therms. 

 About one-half of the total fuel value of these feeds passes off as 

 undigested matter, never having been inside the body proper. 



Such roughages as straw, hay, and corn stover, because of their 

 coarse, woody character due to the fiber they contain, place much 

 work on the animal in digesting them and passing the waste out of 

 the body. This means an evolution of heat. Therefore where the 

 animal, such as an idle horse in winter, is doing no work and needs 

 little net energy, no harm but rather economy in cost of keep may 

 result from living on such roughages, because the large amount of 

 heat necessarily produced in the digestion and assimilation of this 

 food helps keep the animal warm. On the other hand, animals at 

 hard work and those producing milk or being fattened cannot profit- 

 ably live chiefly on coarse forage but must have liberal allowances of 

 concentrates, such as corn or oats, for they need large amounts of net 

 energy in their rations. 



Due to the immense amount of work required in each individual 



trial, the net energy values have as yet been determined for only a 



i small number of feeds. Thus, as we shall see in Chapter VIII, our 



