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



471 



Compuiaiion of energy expenditure of steer E per kilogram of grain eaten 



a Computed from a comparison of periods 4 and 6. 



DIFFERENCES IN LIVE WEIGHT 



As the figures of Table VII show, the live weight of the animals varied 

 more or less in the different periods. To what extent do these varia- 

 tions affect the conclusions drawn from comparisons like those just 

 illustrated ? 



Two effects other than those due directly to the amount of feed might 

 be anticipated from an increase in the live weight: First, an increase in 

 the basal metabolism due to a greater mass of tissue, and, second, an 

 increase in the muscular work of supporting the body in the standing 

 position. As regards the first of these, it is to be remarked that the 

 experimental periods were short (three or, in a few cases, four weeks only) 

 while the changes in the amount and kind of feed consumed were con- 

 siderable. It seems altogether probable that the larger part of the 

 variation in weight must be ascribed to "fill" — i. e., to variations in the 

 contents of the digestive tract rather than to any considerable change in 

 the make-up of the body proper — and that the actual basal metabolism 

 was not greatly affected. As regards the effect upon the muscular work 

 of standing, it has been already pointed out that this appears to be a 

 relatively small factor in the total increase of heat elimination in stand- 

 ing. In view of these considerations, it is to be anticipated that a cor- 

 rection of the heat production in proportion to either the weight or the 

 surface of the animals would materially exaggerate the effect upon the 

 metabolism, and, on the whole, we have regarded it as safer to disregard 

 the variations in live weight rather than to attempt a more or less con- 

 jectural correction. 



