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* 
Alfalfa hay Timothy hay Wheat straw 
Horses ee Horses Bun Horses eae 
Protein .ca crak ued cds 73 74 “21 ) 48 28 23 
IND OP eis'cemnecig canny canon 40 45 43 50 18 55 
Nitrogen-free extract....| 70 72 «|r «47 62. 28 39 
SAGs 3 tesntieud arta wSasenecn eossitce 14 40 47 50 66 36 
Organic matter......... 58 61 44 56 21 | 46 
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: * “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, 
=: 6.4 per cent with the nitrogen-free extract, + 19.6 per cent with 
the crude fat, and ++ 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. 
3 Experiment Station Record, voi. 9, p. 513. 
