129 



digested varying considerably with the kind of food. Of the 

 total organic matter there is on the average about 85 per cent, 

 digestible in concentrated foods (cakes and meals) and in roots. 

 Undecorticated cotton cake and brewers' grains are consider- 

 ably, and oats and bran rather, less digestible. Of the various 

 food constituents the fibre is naturally the least nutritive, al- 

 though large proportions of this, especially in the best concen- 

 trated foods and in green foods, are actually digested. 



Comparative values of foods Endeavours have been 

 made to attach comparative values to carbo-hydrates, albumin- 

 oids, and fats, and so arrive at a method of comparing the com- 

 mercial values of foods. One method suggested is to value the 

 units as follows : Digestible carbo-hydrates and fibre, Is. ; do. 

 albuminoids, 2s. 6d. ; do. fat, 2s. 6d. As, however, each of 

 these varies greatly in commercial value in different foods, and 

 as 110 satisfactory standard of comparison can be made, the 

 systems of valuing foods according to u food units " are gener- 

 ally considered unreliable. 



Table B shows the amount of digestible substances required 

 per day by different classes of animals as determined by Dr. 

 Wolff. 



Example of a daily ration. The following ration con- 

 tains the daily requirements of a dairy cow, of about 1,000 Ib. 

 live weight, and giving 27J Ib. of milk daily. The amounts 

 of digestible ingredients are obtained in each case by multiply- 

 ing the percentages of those contained in each food by the 

 number of pounds of the same fed to the animal daily, and 

 dividing the product by 100. 



This ration comes near the standard, as is shown by com- 

 paring the figures in the two last lines. The digestible carbo- 

 hydrates and fibre, as well as the fat, are rather high, but are 

 quite near enough for practical purposes. The elaborate feed- 

 ing experiments which have been made at Cockle Park and at 

 Offerton Hall have all tended to show the approximate correct- 



9 



