THE DIGESTIBILITY OF FEEDING STUFFS. 



513 



In calculating the digestibility of wheat bran from the results of the 

 experiment with meadow hay and bran the figures obtained for meadow- 

 hay when fed alone must be employed. The errors attaching to the 

 latter figures are therefore transmitted to the figures for wheat bran, 

 and amount to the following in percentage of the constituents of the 

 wheat bran: 



Variations in digestibility of wheat bran. 



In 2 kg. 

 of wheat 



brau. 



Variations in the coeffi- 

 cients of digestibility. 



Average. Maximum. 



Dry matter 



( Organic matter 



Crude protein 



Nitrogen- free extract 



Crude t';it 



Crude liber 



Grams. 

 1,736 



l,<>20 

 282 



1.120 



74 



144 



Per cent. 

 4.0 

 4.0 

 6.3 

 3.5 

 8.1 

 22. 9 



Per cent. 

 15. 4 



15. :s 



is. l 

 12.lt 



:;9.2 

 77.1 



Hence, when only two experiments are made, one with hay and the 

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

 digestibility obtained by the most careful work may vary from the 

 actual by dL 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 experi- 

 ments give results of very uncertain value, which are almost entirely 

 lacking in significance. Weight can be given only to the averages of 

 many experiments, and only such averages can be regarded as decisive. 

 This should be borne in mind, especially in cases in which comparative 

 experiments are made with the same feeding stuff prepared for feeding 

 in different ways, or on the effect on the digestibility of some added 

 material. 



