106 VETEEINAEY HYGIENE 



the proteid, fat, and carbo-hydrate in it. The amount of 

 these which are absorbed under favourable conditions is 

 fairly definite, but under unfavourable conditions, such as 

 the food being 'badly saved,' or there being too much carbo- 

 hydrate present, or too much or too little proteid in the diet, 

 the amount absorbed departs from the normal, and less is 

 extracted or less stored up than would have been the case 

 had conditions been favourable. 



Every food given to animals has a portion of its nutritive 

 matter unacted upon, which is excreted with the faeces, 

 together with such indigestible substances as lignin. 



The amount of nutritive matter absorbed from each food- 

 stuff varies with the class of animal, the nature of the food, 

 and its state of preservation. It is the same for each food, 

 and each class of animal, provided the digestive apparatus 

 is in good working order, though of course there are some 

 marked individual differences. 



The amount absorbed cannot be increased or decreased 

 by the amount of food given ; the proportion absorbed is 

 quite independent of the amount supplied. Further, it is 

 quite unaffected by rest or work. The only thing which 

 seriously affects the amount of nutritive principles absorbed, 

 and causes them to depart from the normal, is the pro- 

 portion which the non-nitrogenous principles bear to the 

 nitrogenous in a mixed diet. 



The amount of absorbed proximate principles of any food. 

 is expressed as a percentage of the total amount supplied ; 

 thus 69 per cent, of the proteids in hay are digested by a 

 horse ; 90 per cent, of the fat in linseed cake are digested 

 by cattle, and 39 per cent, of the carbo-hydrates in straw are 

 digested by sheep. These numbers are termed the Diges- 

 tive Coefficient, and are expressed by saying the coefficient 

 of digestion of the proteids in hay is 69, of fat in oil-cake is 

 90, of carbo-hydrates in straw is 39. 



Here is a table* of digestive coefficients for horses, 

 oxen, and sheep, of the principal feeding stuffs. It must 



* Extracted from a series of elaborate tables by Prof. Emil v. "Wolff, 

 ' Farm Foods.' 



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