Mar. 2s. 191S Energy Values of Feeding Stuffs for Cattle 445 



The results recorded in Table III illustrate the familiar fact that the 

 greatest loss of chemical energy, especially in the case of coarse feeds, 

 is that in the undigested feed residues of the feces and in the relatively 

 small amounts of excretory products which, in the case of cattle, accom- 

 pany them. The relative proportions lost in the urine and in the methane 

 naturally vary with the composition of the feed, one rich in protein tend- 

 ing especially to increase the energy content of the urine, while carbohy- 

 drates tend to increase the excretion of methane. 



Of greater interest, however, is the variability of the losses suffered 

 by the same feeding stuff in different periods. 



INFLUENCE OF QUANTITY OF FEED CONSUMED ON LOSSES OF CHEMICAL 



ENERGY 



In considering this question it should be borne in mind that the com- 

 parisons here reported are in every instance between different amounts of 

 the same ration — i. e., they deal with the influence of quantity only and 

 do not touch the question of the influence of heavy grain feeding. Fur- 

 thermore, they relate to comparatively light feeding, many of the periods 

 having been upon submaintenance rations, while the total dry matter 

 of the feed seldom reached 18 pounds per 1,000 pounds of live weight. 

 The experiments recorded in Table III include 31 cases in which different 

 amounts either of a single feeding stuff or of an identical mixed ration 

 were consumed by the same animal in two different periods of the same 

 experiment, under conditions as nearly imiform as it was possible to 

 make them. The results may be most conveniently compared on the 

 basis of the percentage distribution of the energy, as shown in the last 

 four columns of the table. In the following comparisons the results 

 computed by difference for the concentrated feeds are not included. 



LOSSES IN METHANE 



In a single instance (alfalfa hay and grain mixture No. 2 in experiment 

 208, steer E, periods 2 and 3) the percentage loss in the methane was 

 greater on the heavier of the two rations and in another case (corn stover 

 in experiment 210, steer D, periods i and 2) the difference was only 

 o.oi per cent. In two cases the determinations of methane are believed 

 to have been inaccurate. In the remaining 29 cases the percentage 

 loss in methane was distinctly greater on the lighter ration, the differ- 

 ence ranging from o. 11 to 2 per cent and tending, on the whole, to be 

 somewhat greater on the mixed rations, with their larger proportion of 

 readily soluble carbohydrates, than on those consisting exclusively of 

 coarse fodder. In other words, as would be anticipated, the bacterial 

 fermentation of the carbohydrates in the digestive tract of cattle pro- 

 ceeds to a distinctly greater extent on light than on heavy rations. 



LOSSES IN URINE 



The percentage of the feed energy excreted in the urine was also greater 

 on the lighter ration in 28 cases out of 33, the exceptions being two 

 experiments on alfalfa hay (experiment 208, steer E, periods 5 and 6, 



