22 



MAINTENANCE RATIONS OF FARM ANIMALS. 



periinent, the following percentages were found to be available in the above 

 sense, while the remainder simply served to increase the heat production : 



Average availability of metabolizable energy. 



Per cent. 



Timothy hay, 5 experiments 56.32 



Clover hay, 2 experiments 58. 47 



Corn meal, 1 experiment 69. 12 



Wheat bran, 2 experiments 55. 36 



Mixed grain (1 part wheat bran, 3 parts corn meal, 3 parts 



linseed meal O. P. ) , 4 experiments 57. 42 



Kellner's 1 extensive investigations upon the metabolism of fattening cattle 

 have likewise demonstrated that in the productive feeding of these animals 

 only part of the metabolizable energy supplied in excess of the maintenance 

 ration is recovered in the gain produced, the remainder being converted into 

 heat, so that the heat production increases with the amount of feed consumed. 



AVAILABILITY FOR THE HORSE ZUNTZ AND HAGEMANN'S RESULTS. 



The foregoing results upon cattle have been cited because they 

 illustrate simply and clearly the basic conception of the availability 

 of feed energy and also because they are, so far as the writer is 

 aware, the first experiments upon farm animals on submaintenance 

 rations in which the complete balance of matter and of energy for 24 

 hours has been determined. Zuntz and Hagemann 2 , however, had 

 shown several years before in an extensive investigation that the in- 

 creased metabolism which Zuntz and his associates had observed in 

 dogs and men as resulting from the ingestion of food was even more 

 marked in the case of the horse. 



In their investigations the respiratory exchange of the animal was determined 

 by the Zuntz method in short periods at various intervals after the consump- 

 tion of more or less diverse rations, a small correction being added for cuta- 

 neous and intestinal respiration. By combining these results with those of a 

 number of separate digestion trials in which the nitrogen and carbon of the 

 feed and of the visible excreta were determined, an approximate determination 

 of the total energy metabolism of the animal was also possible. 3 



For example, on the average of a number of experiments in which the metab- 

 olism shortly before feeding in the morning, shortly after feeding, and some 

 hours later was determined by the methods just outlined, the following results, 

 computed per kilogram per minute were obtained.* 



Energy- 

 liberated. 



Fasting 



36 minutes after feeding 

 hours after feeding. . . 



Gram- 

 calories. 

 16. 929 

 18.510 

 18. 787 



1 Die Landwirtschaftlichen Versuchs-Stationen, Band 53, and Ermihrung der Land- 

 wirtshaftlichen Nutztiere. 



2 Landwirtschaftliche Jahrbiicher, vol. 27, Ergiinzungsband III. 



3 For a more complete account of the method, compare Armsby, Principles of Animal 

 Nutrition, pp. 386-387. 



* Loc. cit., p. 282. 



