226 



Concentrated Feeding-stuffs. 



[JUNE, 



In this example two foods composed of practically the same 

 ingredients are compared, and the assumption has been made 

 that they are therefore of equal digestibility. If the foods 

 are of similar character, but composed of different ingredients 

 {e.g., a linseed cake and a soy bean cake), the procedure 

 is precisely the same except that the percentages of digestible 

 albuminoids, &c, must first be calculated in each case from 

 the guaranteed percentages of total albuminoids, &c, and 

 then the sum of the digestible food units calculated from 

 them. The following example will illustrate this case. 



Example II. — Suppose it is desired to compare the linseed 

 Cake A (Example I.) with a decorticated cotton cake contain- 

 ing 40 per cent, of albuminoids, 9 per cent, of oil and 72 per 

 cent, of carbohydrates at £8 15s. per ton. 



Using the data given in the Table on p. 225, the percentages 

 of digestible nutrients in these foods are obtained as 

 follows : — 





Linseed Cake. 



Decorticated Cotton Cake. 



Total. 



Digestible. 



Total. Digestible. 



Albuminoids 



Oil 



Carbohydrates 



Per cent. Per cent. 

 86 

 100 



II =IO 

 IOO 



34 xii =2 6i 



IOO 



Per cent. Per cent. 

 4 o xJ* =34i 



IOO 



9 x94 = Sh 



IOO 



27 x&L =js 



IOO 



Then the total numbers of digestible food-units in each 

 case are : — 



Linseed Cake ... (27 \ + 10) x 2| + 26| = 120 

 Decort. Cotton Cake (34^ + 8£) x 2 J + 18 =125 



The cost per digestible food-unit of the linseed cake is 



^9 = is. 6d. At this rate the decorticated cotton cake should 

 120 



be worth 125 x is. 6d., or £q ys. 6d. per ton. 



In this method of comparing the prices of feeding-stuffs 

 it is assumed that the differences in manure-values will be 

 sufficiently allowed for in the high value that is assigned to 

 the albuminoids, since it is the nitrogen contained therein 

 that mainly determines the differences in manure-value 

 between different foods. 



