Mar. 25. 1915 Energy Values of Feeding Stuffs for Cattle 453 



Metabolizable energy of feeding stuffs per kilogram of digestible organic matter 



Therms. 



Coarse feeds 3. 5 



Concentrated feeds: 



With less than 5 per cent of digestible fat 3. 9 



With more than 5 per cent of digestible fat 4. o 



No similar results have been reported on succulent feeds, with the 

 exception of Zaitschek's figure for pumpkins. 



II. EXPENDITURE OF ENERGY CONSEQUENT UPON FEED CONSUMP- 

 TION AND ITS FACTORS 



That the consumption of feed tends to increase the metabolism of an 

 animal has become a commonplace of physiology. The magnitude of 

 the effect varies within rather wide limits according to the chemical and 

 physical properties of the feed, while there is still more or less difference 

 of opinion as to its causes. Zuntz and his associates have called it 

 "work of digestion" and have attributed it largely to increased muscular 

 and glandular activity of the digestive and excretory organs. Most 

 physiological investigations in this field have been made on camivora or 

 on man, in which the increase of the metabolism is not usually very 

 large, except when much protein is consumed. More recent investiga- 

 tions on these species appear to have shown that the mechanical work of 

 the digestive organs is but a small factor and that the term "work of 

 digestion" is not a fortunate one. With herbivora and especially with 

 ruminants, however, the total effect on the metabolism is quantitatively 

 very marked, while the mechanical factor is of much greater significance. 

 This was early shown by Zuntz and Hagemann (52) in their investiga- 

 tions upon the horse. With ruminants the most extensive investiga- 

 tions are those made at the Mockern (Germany) Experiment Station by 

 G. Klihn (29) and by Kellner (24, 25, 26, 27). These investigations, 

 especially those of Kellner, were directed primarily to the determination 

 of the relative values of nutrients and feeding stuffs, but from another 

 point of view they constituted also determinations of the energy expendi- 

 ture caused by the feed. The main purpose of the experiments here 

 reported was to determine the proportion of the feed energy expended 

 in the increased metabolism by means of direct measurements of the heat 

 evolved, checked by determinations of the respiratory products, the 

 relative values of the feeding stuffs being obtained by difference. 



DIFFERENCES IN MUSCULAR .\CTIVITY 

 INFLUENCE OP STANDING OR LYING UPON METABOLISM 



We have repeatedly called attention to the very striking increase in 

 the heat elimination of cattle when standing as compared with that when 

 lying and have shown (11), in reply to the criticism of Zuntz, that it is 



