OIECUMSTANCBS AFFECTING DIGESTIBILITY 163 



the added food is entirely digested without the rate of 

 digestion of the original food being sensibly altered. 

 The same result has been obtained in experiments with 

 pigs fed on potatoes, to which variable quantities of 

 meat flour were afterwards added : the albuminoids 

 of the meat were entirely digested, while the propor- 

 tion of the potatoes digested remained unchanged. 



An addition of oil (olive, poppy, and rape oil) to a 

 diet of hay and straw is also apparently without 

 unfavourable influence on the rate of digestion ; 

 indeed, some experiments with small quantities of 

 oil (^ lb. of oil per day per 1,000 lbs. live weight) 

 show an improved digestion of the dry fodder. Oil 

 supplied in moderate quantities is itself entirely 

 digested. 



An addition of starch or sugar to a diet of hay or 

 straw will, on the contrary, diminish its digestibihty, 

 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 digestibility if the amount of carbo- 

 hydrate added is considerable. When starch has been 

 added, it is itself completely digested, if the ratio of 

 the nitrogenous to the non-nitrogenous constituents 

 of the diet (see p. 163) is not less than 1 : 8. 



These facts are of considerable practical importance. 

 Nitrogenous foods, as oilcake 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 diminish- 

 ing the digestibility of the latter. This decrease in 



