290 



ALBUMINOID RATIO 



The pig possesses good digestive power for highly concentrated 

 foods, but the shortness of its digestive canal seriously lessens the 

 amount of crude fibre and of bulky fodder which it can digest. 



Horses show similar inferiority in digestive power when compared 

 with ruminants. With protein, however, they are, on the whole, as 

 well able to deal, but with carbohydrates, fats and especially fibre they 

 are distinctly inferior to cattle and sheep. 



Fodder is subject to the greatest variation in digestibility, being 

 almost always most digestible when young. This is true, manifestly, 

 with reference to the " fibre," which becomes less and less digestible 

 as the plant becomes more lignified, but also applies to the proteids, 

 fat and starch. This is well seen by reference to the digestion co- 

 efficients for hay and green grass, clover, etc., in the table just given. 



Albuminoid Ratio. It is found that the digestibility of some 

 constituents may be altered by the addition to the food of an increased 

 quantity of one constituent. This is only true under certain circum- 

 stances, viz., when the albuminoid ratio of the food is changed so as 

 to fall outside certain limits, which differ with the particular animal 

 considered. By albuminoid ratio or nutritive ratio is meant the ratio 

 of the digestible albuminoids to the digestible non-albuminoids ex- 

 pressed in equivalent of starch. The calculation of the starch equi- 

 valent of fat, sugar, etc., is based upon the results of calorimetric 

 experiments, i.e., the quantities which will produce, by their combus- 

 tion, an equal amount of heat. 



By placing an animal in a respiration calorimeter, so arranged that 

 everything which enters and leaves may be measured, the quantities 

 of various dry foodstuffs which will produce, in the body of the animal, 

 as much heat as 100 parts of fat has been determined. The following 

 table gives the results as compared with those obtained by direct oxida- 

 tion of the food in a combustion calorimeter * : 



The agreement between these two sets of numbers is as close as can 

 be expected. 



Eubner gives the following as the approximate heats of combustion 

 of the three principal classes of food : 



1 Eubner, quoted by Atwater, Bull. 21, U.S. Dept. of Agric. Atwater found, 

 as a mean, that the heats of combustion of the available fat, protein and carbo- 

 hydrates of foods were represented by 9400, 4400, and 4100 thermal units (Hep. of 

 the Storrs Agric. Expt. Station, 1899). These numbers agree well with the older 

 numbers obtained by Eubner in 1885. 



