i9i i.] Starch Equivalents of Feeding Stuffs. 723 



to much painstaking work, which has been carried out largely 

 in Germany and elsewhere on the Continent, and also in the 

 United States, we are furnished with the digestibility co- 

 efficients of the nutrients in almost all feeding stuffs, and in 

 most cases where tables of the chemical analysis of foods are 

 given it is also indicated what amount can be regarded as 

 digestible. Naturally the figures which are quoted refer to 

 the feeding stuffs and animals actually concerned, but it is 

 not likely that we should find very marked differences in the 

 results if similar trials were made with British foods and 

 stock. As up to the present practically no such information 

 is available from home sources, the data supplied by others 

 must be used. When therefore an average feeding stuff is 

 being considered, the commonly accepted digestibility co- 

 efficients must be used. Much valuable information in this 

 connection is contained in a table compiled by Dr. Chas. 

 Crowther, and published by the University of Leeds. The 

 figures, both for the total and the digestible constituents, 

 apply .to good average feeding stuffs. The leaflets referred to 

 above, as well as most text-books on the subject, contain 

 similar tables. 



Availability of Foods. — Another point to be considered in 

 connection with a feeding stuff is its availability. From 

 whatever food, even the most digestible that an animal eats, a 

 certain deduction has to be made for that part of it, or rather, 

 the energy of that part of it, which is used up in the animal 

 itself, chiefly in the processes of mastication and digestion. 

 No true comparison can be made between the digestible 

 nutrients in one feeding stuff and those in another unless 

 the foods themselves are similar with regard to the form in 

 which the nutrients are present. To take the digestible 

 materials in oat straw as determined by chemical analysis 

 and by actual digestibility trials with animals and compare 

 them directly with what is found when linseed cake is treated 

 in an analogous manner would not give us reliable information 

 regarding the comparative feeding value of the two foods 

 in question. If instead of oat straw we compared wheat straw 

 with linseed cake the comparison would be even less reliable, 

 for the nutrients in wheat straw have to bear a greater 

 deduction than is the case with oat straw. This is because 



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