Mar. 25, 191S Energy Values of Feeding Stuffs for Cattle 447 



reappear in the feces, the result will be a relative increase in the metab- 

 olizable energy. On the other hand, if the greater fermentation on 

 the lighter rations is at the expense of the more soluble carbohydrates 

 which would otherwise be digested by the enzyms of the intestines, the 

 metabolizable energy will be diminished by the quantity of chemical 

 energy escaping in the methane (and urine). It is perhaps not sur- 

 prising, therefore, to find that the effect of the quantity of feed upon the 

 percentage of energy metabolizable was somewhat variable. 



In 19 out of 22 cases mentioned in the previous paragraph in which 

 the percentage loss of energy in the feces decreased as the amount of 

 feed consumed was diminished, the percentage of energy metaboUzed 

 did in fact increase, while in the remaining 3 cases the greater losses in 

 methane and urine overbalanced the effect of the increased digestibiUty. 

 In each of the 10 instances in which the percentage loss of energy in 

 the feces was greater on the lighter rations, the percentage metabohzable 

 shows a corresponding decrease, so that of the entire 33 comparisons 

 14 show a greater and 19 a less percentage metabolizable on Ughter as 

 compared with heavier rations. 



On the whole, then, the differences in amount of feed consumed, within 

 the limits of these experiments, failed to show any unmistakable effect 

 upon the quantity of energy actually liberated in the body from a unit 

 weight of feed. Morever, it must be borne in mind that a considerable 

 part of the additional energy secured by the more extensive fermenta- 

 tion of the lighter ration is liberated in the digestive tract as heat of 

 fermentation and does not enter into the energy exchange of the body 

 tissues, so that the difference in the net nutritive effect is hkely to be 

 less than that in the metabolizable energy as ordinarily defined. 



INFLUENCE OF INDIVIDUALITY ON LOSSES OF CHEMICAL ENERGY 



In five of the experiments the same feeding stuff or mixture of feeding 

 stuffs was fed to more than one animal, although unfortimately the 

 amoimts consumed were not the same either per head or in proportion 

 to the live weight, so that exact comparisons are not possible. 



In experiments 190, 200, and 207 a pure-bred Shorthorn steer was com- 

 pared with a so-called scrub. A comparison of the averages for the 

 Ughter and the heavier rations of timothy hay, respectively, for the 

 three successive years gives the averages shown in Table V, which fail 

 to show any distinct individual difference between the two animals. 

 The results computed by difference for the wheat bran in experiment 

 190 and for the grain mixture No. i in experiments 200 and 207 show 

 somewhat larger numerical differences, but when the errors incident to 

 such calculations by difference are considered they agree with those 

 upon hay in showing no material difference between these two animals. 

 This point has been discussed from a slightly different standpoint else- 

 where (10). 



