92 HEALTH AND DISEASE 



contrary, diminish its digestibility, if the amount added exceeds 10 per cent 

 of the dry fodder. The albuminoids of the food suffer the greatest loss of 

 digestibility under these circumstances. The fibre also suffers in digesti- 

 bility if the amount of carbohydrate added is considerable. When starch 

 has been added, it is itself completely digested if the ratio of the nitro- 

 genous constituents of the diet is not less than 1 in 8. 



These facts are of considerable practical importance. Nitrogenous foods, 

 as oil-cake and bean-meal, may be given with hay and straw chaff without 

 affecting their digestibility, but foods rich in carbohydrates, as potatoes 

 and mangels, cannot be given in greater proportion than 15 per cent of the 

 fodder (both reckoned as dry food) without more or less diminishing the 

 digestibility of the latter. This decrease in digestibility may, however, be 

 counteracted in great measure by supplying with the potatoes or mangels 

 some nitrogenous food. When this is done, the proportions of roots or 

 potatoes may be double that just mentioned without a serious loss of 

 digestibility. Potatoes exercise a greater depressing effect on the digesti- 

 bility of hay than roots, starch being more potent in this respect than 

 sugar. The cereal grains are rich in starch, but contain also a fair propor- 

 tion of albuminoids. They may be added to a dry fodder without seriously 

 affecting its digestibility if the ratio of the nitrogenous to the non-nitro- 

 genous constituents of the diet does not fall below 1 in 8. 



Common salt is well known to be a useful addition to the food of 

 animals. It is stated to quicken the conversion of starch into sugar by the 

 saliva and pancreatic juice. When sodium salts are deficient in the food, 

 salt supplies the blood with a necessary constituent. Sodium salts are 

 tolerably abundant in mangels and small in quantity in hay; they are 

 absent in potatoes, and generally absent in grain of all kinds. 



SYSTEM OF FEEDING 



Quantity and Quality. — It is recognized as a principle in feeding- 

 animals that the quantity and quality of the food should bear a distinct 

 relation to the purpose for which the animal is intended. With reference 

 to the horse, it is always the case that the immediate object is to preserve 

 the animal's health and condition, so that he may be able to do the largest 

 amount of work without injury. With cattle, sheep, and swine, the atten- 

 tion of the feeder is directed towards the attainment of as much fat and 

 flesh as it is possible to derive from the food with which the animal is 

 supplied. With this system of fattening animals for the purpose of food 

 the horse-owner has absolutely no concern, and the system, therefore, is 

 considerably simplified, as the horse-owner is only required to exercise his 



