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ANNUAL REPORT OF THE 



Off. Doc. 



giving as before an anionnt containing just 1,000 units of energy, and 

 that in this experiment, we find tliat the production of heat is in- 

 creased by o«lj 400 units, while the gain of tissue is equal to GOO 

 units; in this case, the availability is plainly 60 per cent, while only 

 40 per cent, is required for digestion and assimilation. In "other 

 words, a given number of units of energy in the second feeding stuff 

 is worth one and )ie half times as n.u.h '^oi ofowth or fattening as 

 the same number of units of energy in the first feeding stuff. 



In the above illustrations, round numbers have purposely been 

 used to illustrate the principle. Let us now turn for a further illus- 

 tration to the results of actual experiments and consider some recent 

 German results, obtained by a slightly different method but having 

 substantially the same significance. After making a deduction for 

 the energy of the indigestible matter, it w^as found that one gram 

 of the digestible matter from the foUovving feeding stuffs contained 

 the amounts of total energy shown in the first column. Of this 

 energy, the quality shown in the second column served simply to 

 increase the heat production of the animal, while the remainder, as 

 stated in the third column, was available for tissue-production. 

 While of this the amounts shown in the second column were availa- 

 ble for tissue production. Finally, by dividing the third column by 

 the first, we compute the percentage availability of the energy of 

 these different materials. 



As yet comparatively few feeding stuffs have been investigated in 

 this way while we are but just beginning to sketch out the general 

 raws governing the availability of feeding stuffs. The much dis- 

 cussed question of the nutritive value of the w'oody fiber of food is 

 a good illustration of this. The earlier writers on stock feeding 

 considered it to have no value whatever. Then came experiments 

 which showed thai a large proportion of it was apparently digesti- 

 ble by rnminants. and on chemical evidence the digestible portion 

 was assumed to have substantially the same nutritive value as 

 starch or sugar. Still later, it was shown that much at least of its 



