136 SCIENTIFIC FEEDING OF ANIMALS 



The artificial drying of food-stuffs at fairly high 

 temperatures diminishes, as a rule, the digestibility 

 of the protein. Sometimes other constituents of 

 the food are also rendered less digestible, particu- 

 larly when by use of the furnace gases a partial 

 charring of the substance takes place. It has been 

 shown by comparative experiments, however, that 

 with turnip slices and potatoes the dry material 

 obtained by the use of furnace gases is quite as 

 good as that dried by steam if the temperature is 

 carefully regulated. 



Turnip or mangel tops are most difficult to dry 

 successfully, for the tender leaves are very apt to 

 char whilst the fleshy part of the top is still 

 undried. As a result it often happens that the 

 leaves are quite black and the digestibility of them 

 greatly diminished. The average coefficient of 

 digestibility for the crude protein in dried turnip 

 leaves was found to be 40-50%, whilst the diges- 

 tibility of the fresh material was 74%. 



When a high temperature acts upon succulent 

 food-stuffs the proteins are converted into other 

 forms, which resist the digestive juices. The 

 nitrogen-free extract substances are not injured by 

 drying unless the material is actually charred. 



