676 NUTRITION OF FARM ANIMALS 



that food consumption increased the total metabolism by about g per 

 cent of the metabolizable energy of the food eaten. Zuntz and Hage- 

 mann assume that this result is applicable to the digestible nutrients 

 of the feed of the horse. 



In addition, it was found that hay produced a much more marked 

 effect than did grain in augmenting the heat production of the horse 

 as estimated from the respiratory exchange, which was determined 

 by means of the Zuntz apparatus in short periods at various intervals 

 after the consumption of more or less diverse rations, a small correc- 

 tion being added for cutaneous and intestinal respiration. This dif- 

 ference is ascribed to the crude fiber of the hay and its amount is 

 computed to be 2.086 Cals. per gram. The energy expended in the 

 mastication of the feed is likewise related to its crude fiber content, 

 being estimated at 0.565 Cals. per gram. The total heat increment 

 per gram of crude fiber, therefore, is estimated at 2.65 Cals. per gram. 



778. Computation of net energy value. In brief, Zuntz 

 and Hagemann compute the heat production due to the con- 

 sumption of feed by the horse to be equal to 9 per cent of 

 the metabolizable energy, estimated at the rate of 3.96 Cals. 

 per gram of digestible nutrients, plus 2.65 Cals. for each gram 

 of total crude fiber present, and by subtraction of these amounts 

 from the metabolizable energy obtain the net energy value. 



The method of computation may be conveniently illustrated 

 from the data given by Langworthy 1 for timothy hay. Zuntz 

 and Hagemann 's factors, recalculated per 100 pounds for 

 convenience, become for metabolizable energy 1.796 Therms 

 and for crude fiber 1.202 Therms. On this basis the calculation 

 of the heat production due to the hay would be as follows : 



TABLE 211. COMPUTATION OF NET ENERGY VALUE PER 100 POUNDS 

 FOR THE HORSE 



Digestible nutrients 



Protein ......... 1.25 Ib. 



Crude fiber 12.39 Ib. 



Nitrogen -free extract 21.29 Ib. .tUTTi;? ' 



Fat (1.18 X 2.4) 2.83 Ib. 



37-72 Ib. 

 Total crude fiber 29.00 Ib. 



Metabolizable energy 1.796 Therms X 37-72 = 67.75 Therms 



Increase of metabolism 



9 per cent of metabolizable energy 67.75 Therms X 0.09 = 6.10 Therms 

 Additional for crude fiber . . . 1.202 Therms X 29.00 = 34.86 Therms 

 Total 40.96 Therms 



Net energy value 26.79 Therms 



1 U. S. Dept. Agr., Office of Expt. Stas., Bui- 125, p. 14. 



