64 



PRINCIPLES OF FEEDING FARM ANIMALS 



hay, and wheat straw by horses and ruminants will show the extent 

 of the differences observed : 



Digestion Coefficients for Horses and Ruminants, in Per Cent 2 



The coarser and less valuable a feeding stuff is, the greater is the 

 difference in the digestibility coefficients obtained with the two 

 kinds of animals. With concentrates no appreciable difference has, 

 however, been observed in the digestibility by ruminants and other 

 farm animals : 77 per cent of the protein of oats is thus digested by 

 sheep and 79 per cent by horses ; the latter digest 76 per cent of the 

 protein in corn, and sheep digest 78 per cent. Digestion experiments 

 with swine have shown that, generally speaking, these animals digest 

 their feed to a similar extent as horses or ruminants. The differ- 

 ences which have been observed in the digestion coefficients are small 

 and more likely to have been caused by experimental errors in the 

 technique of digestion trials than by actual differences in the digesti- 

 bility of the feeds. The experimental errors in determining the 

 digestibility of concentrates are considerable, especially in the case 

 of animals that cannot be fed such feeds alone, and it is only by 

 repeated digestion trials under different conditions as to animals, 

 amounts fed, combinations with other feeds, etc., that the results can 

 be considered trustworthy. Kellner concluded from his investiga- 

 tions of this point : 3 " When only -two experiments are made, one 

 with hay and the other with hay and wheat bran, there is danger that 

 the coefficients of digestibility obtained by the most careful work may 

 vary from the actual by ± 9 per cent in the case of crude protein, 

 =t 6.4 per cent with the nitrogen-free extract, ± 19.6 per cent with 

 the crude fat, and =fc 38.5 per cent with the crude fiber. It is plain 

 from this that single experiments give results of very uncertain value, 

 which are almost entirely lacking in significance. Weight can be 

 only given to the averages of many experiments, and only such 

 averages can be regarded as decisive." 



2 Massachusetts Report, 1911. 

 •Experiment Station Record, vol. 9, p. 513. 



