106 THE CHEMISTRY OP THE FARM. 



mentioned without a serious loss of digestibility. Potatos 

 exercise a greater depressing effect on the digestibility 

 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 proportion of albuminoids ; they may 

 be added to dry fodder without seriously affecting its 

 digestibility, if the ratio of the nitrogenous to the 

 non-nitrogenous constituents of the diet does not fall 

 below 1:8. 



Common salt is well known to be a useful addition to 

 the food of animals. It is stated to quicken the conver- 

 sion 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 potatos, and generally absent 

 in grain of all kinds. 



Comparative Nutritive Value of Poods. Having 

 made ourselves acquainted both with the composition, 

 and the degree of digestibility of ordinary cattle foods, 

 we are now in a position to enter on some general consider- 

 ations as to their relative feeding value. The following 

 table shows the quantity of digestible nutritive matter 

 in 1000 Ibs. of ordinary foods when supplied to sheep or 

 oxen. The carbo-hydrates in the table include digestible 

 cellulose. In calculating the amount of digestible albu- 

 minoids it has been assumed that in the original diges- 

 tion experiment the amides and nitrates present, being 

 soluble bodies, have been reckoned as digestible 

 albumin. 



