96 



HEALTH AND DISEASE 



METHODS OF CALCULATING THE NUTRITIVE VALUE OF 

 DIFFERENT ARTICLES OF DIET 



For ordinary purposes the horse-owner will be content to refer to what 

 has already been stated for the purpose of deciding what article of diet will 

 be most useful and economical, but the German and French investigators 

 have not been content with this general knowledge, and we are indebted to 

 them for a number of interesting and important experiments, the outcome 

 of which is to enable the curious in such matters to calculate with almost 

 mathematical accuracy the exact relation which the food bears to its digest- 

 ibility and to the waste of the system. 



It appears that the power of assimilation in different animals varies 

 very considerably in reference to the various constituents of food; thus a 

 horse will digest, out of every 100 parts of mixed diet, 69 parts of albumi- 

 noids, 59 of fatty matters, 68 of the carbohydrates (starch, sugar, and 

 gum), and 33 of cellulose and fibre. The annexed table will show the 

 difference in these respects of the digestive powers of the ox, cow, and 

 sheep : — 



A further analysis indicates that the above proximate principles are 

 differently digested in different articles of food, as shown by the table on 

 p. 97, which relates to the digestibility of the proximate principles of 

 different kinds of food by horses. 



Various circumstances appear to modify the digestibility of different 

 articles of diet. Age and mode of growth and preparation are among the 

 modifying influences. Young plants are more digestible than mature ones, 

 and the digestibility of old hay is less than that of new. It is also stated 

 by the authorities which have been referred to that the digestibility of food 

 is not affected by the amount which the animal consumes, neither is it 

 altered by the amount of labour which the animal performs. According 

 to Wolff, however, the addition of one food will alter the digestibility of 

 another. Thus starch or sugar added to a diet of hay or straw in a larger 

 amount than 10 per cent lessens its digestibility, especially in regard to the 

 albuminoids which the food contains. 



