470 



Journal of Agricultural Research 



Vol. in. No. 6 



The comparison of these two periods shows that each additional kilo- 

 gram of dry matter consumed increased the total heat production by 

 903 Calories, 173 of which represent energy expended in standing, 9 that 

 expended in rising and lying down, and 154 the additional heat due to 

 the methane fermentation, while the remainder, 567 Calories, represents 

 the increased mechanical work of digestion plus any stimulus which the 

 digested nutrients exerted upon the cell metabolism. Obviously the 

 calculation by difference eliminates the basal metabolism. 



For concentrated feeds, which can not be fed alone, two methods 

 have been used, as already noted. In the earlier experiments, the con- 

 centrate was added to the basal ration of coarse fodder. Thus, in period 

 2 of the experiment just used as an illustration a mixture of grains (grain 

 mixture No. 2) was added to the basal ration of period 3 with the follow- 

 ing results: 



Computation of energy expenditure by steer A per kilogram of grain eaten 



Each kilogram of dry matter of the grain increased the heat pro- 

 duction by 1,179 Calories, which can be subdivided as before in the 

 proportions shown.' The greater expenditure of energy per kilogram 

 in the case of grain as compared with hay is seen to be due in part to 

 a greater increase of the metabolism of the animal when standing and 

 in part either to increased mechanical work in digestion or more likely to 

 a greater stimulus of the cell metabolism. 



In later experiments (Nos. 208 to 212, inclusive), in place of adding 

 grain to a ration of coarse fodder, the animals received varying quantities 

 of a uniform mixture of coarse fodder and grain, the energy expenditure 

 caused by the total ration being determined substantially in the manner 

 already illustrated. The portion of the increase due to the grain alone 

 was computed by subtracting from the total increase that due to the 

 hay as determined in two or more separate periods on exclusive hay 

 rations.^' The method may be illustrated by the results obtained with 

 steer E in periods i and 3 of experiment 208. 



Logically the results of the comparison should be corrected for the slight difference (2s gm.) in the 

 amount of dry matter of hay consumed. As a matter of fact, however, this correction is insigni6cant in 

 all the experiments, araountinn in the present instance to about i Calorie. 



' When more than two periods of hay fcedina were used the increased heat production per kilogram of 

 hay was computed by comparing the periods on the heaviest and the lightest rations. 



