AVAILABILITY OF ENERGY FOE THE HORSE. 



23 



It was also found that coarse fodder (hay) produced a much more marked 

 effect than did grain. The following comparison of the average of the experi- 

 ments of period c on an exclusive hay diet with that of the experiments of 

 period / on a mixed ration illustrates this fact. 1 





Period c. 



Period /. 



Ration: 



Hay 



hours.. 



kilos.. 



do.... 



2.6 



About 10. 5 



2.8 



4. 75 

 6.00 



Straw 



do.... 





1.00 



Total digested nutrients (fat X 2.4) 



Per kilogram and minute: 



Oxygen consumed 



Carbon dioxid given off 



Energy set free (computed) 



Energy katabolism per day and head 



grams.. 



cubic centimeters. . 



do.... 



gram-calories. . 



calories.. 



4, 125 



3.9837 

 3. 6586 

 19. 552 

 12,450 



5,697 



3. 6986 

 3. 6695 

 18. 339 

 11,678 



DIGESTIVE WORK FOR CRUDE FIBER. 



Zuntz and Hagemann estimate the fuel value of the total digestible nutrients 

 in the feed of the horse (including digestible crude fiber and digestible fat X 

 2.4) at 3.96 calories per gram, and on the basis of experiments on man made by 

 Magnus-Levy in Zuntz's laboratory they assume that 9 per cent of the metabo- 

 lizable energy of the digestible nutrients as thus computed is expended in 

 their digestion. The hay ration of the foregoing table contained 1,572 grams 

 less of (estimated) digestible nutrients than the mixed ration. The corre- 

 sponding expenditure of energy in the digestion of these nutrients (9 per cent 

 of their metabolizable energy) equals 580 calories. Accordingly the energy 

 katabolism should have been 580 calories less in period c than in period /. 

 It was actually 772 calories greater, a difference of 1,352 calories. This differ- 

 ence is ascribed to the presence in the hay ration of 648 grams more of total 

 crude fiber and corresponds to 2.086 calories per gram of the latter. 



WORK OF MASTICATION. 



The foregoing computations relate to the expenditure of energy in the diges- 

 tion of the food after it has entered the stomach. The same authors have also 

 determined the increase in the gaseous exchange caused by mastication, deglu- 

 tition, etc. For this purpose they compare 2 the excretion of carbon dioxid and 

 the consumption of oxygen during the time actually occupied in eating with 

 the corresponding amounts during rest, as shown by the average of a number of 

 experiments made under identical conditions. On the assumption that the pro- 

 tein metabolism is unaltered, the amounts of carbohydrates and fat metabo- 

 lized and the corresponding amounts of energy are calculated. The following 

 is a summary of the results computed per kilogram of feed : 



Energy expended in mastication of 1 kilogram — Zuntz and Hagemann. 



Feed. 



Number 



of 

 experi- 

 ments. 



Oxygen 

 consumed. 



C0 2 

 excreted. 



Equivalent 

 energy. 



Hay 



8 

 8 

 8 

 2 

 7 



Liters. 

 12. 964 

 33.840 

 20. 072 

 7. 133 

 6. 171 



Liters. 

 10.679 

 27.813 

 17.677 

 6.205 

 4.980 



Calories. 

 64. 17 

 167. 44 

 100. 79 

 35.72 

 30.42 

 47.00 

 13.80 



Hay, oats, and cut straw 



Maize and cut straw (6:1) 



Green alfalfa 





















1 Loc. cit, pp. 276-279. 2 Loc. cit., p. 271. 



