380 Journal of the Department of Agriculture. 



procedure as iu the case of fertilizer's it would be possible to arrive at a 

 list of unit values for each of these constituents, but, as previously 

 explained, it is not proposed to do this. 



It is, however, generally assumed that the comparative value of 

 the protein and fat in all foods is approximately equal, and that each 

 is equal to two and a half times the value of an equal weight of 

 soluble carbohydrates. On this assumption 1 per cent, of the soluble 

 carbohydrates in a ton. i.e. 20 lb., is taken as a unit, so that the total 

 number of food units in the substance is found by multiplying the 

 sum of the percentages of the protein and the fat by 2.5, and add to 

 that sum the percentage of the soluble carbohydrates. Thus : 



jSTumber of food units = 2.5 (protein + fat) + soluble carbo- 

 hydrates. 



■ Comparative Valuation of Feeding Stuffs. 



If we divide the price per ton of any food by the number of food 

 units we get the monetary value of one food unit in it. By going 

 through this calculation for all the different farm foods at present on 

 the South African market it is found that the average value per food 

 unit comes approximately to 2s. 3d., taking in every case the cash 

 retail price per ton, in bags f .o.r. at the works or place of retail. 



This calculated average unit value can be taken as a guide for 

 estimating the commercial value of any particular feeding stuff offered 

 for sale, and to see whether the retail price at which it is offered com- 

 pares favourably or not with this estimate. To give an example, 

 suppose a farm food was placed on tlie market at £15 per ton, having 

 the following constituents guaranteed : — 



Protein, 40 per cent. ; fat, 10 per cent. ; and soluble carbo- 

 hydrates, 30 per cent. ; total number of food units = 

 2.\5(40+10)+30==155; estimated value == 2s. 3d. x 155 = 

 £17. 9s. 



This calculation shows that the retail price of such a food would 

 be considerably below the average market value of these foods at the 

 present time. 



But, as shown in connection with lime manures, we can compare 

 the value of two or more different foods without assuming the correct- 

 ness of the unit value given in the previous paragraph. For instance, 

 suppose two oilcakes were offered for sale, of which the particulars 

 are as follows : — 



No. 1. — -Price, £11. 10s. per ton; guaranteed protein, 43.5 per 

 cent. ; fat, 8.5 per cent. ; soluble carbohvdrates, 26.0 per 

 cent.; number of food units = 2.5 (43.5V 8.5) + 26.0 - 

 156; value of one food unit = £11. 10s. -^ 156 = Is. 6d. 



No. 2. — Price, £9 per ton; guaranteed protein, 43.8 per cent. ; 

 fat, 9.2 per cent. ; soluble carbohydrates, 22.0 per cent. ; 

 number of food units = 2.5(43.8 + 9.2) + 22.0 = 154.5; 

 value of one food unit == £9 -^ 154.5 =^ Is. 2d. 



The second cake is therefore the better value to the buyer, as 

 being 4d. per unit cheaper. 



It must be pointed out, however, that it is not always the food 

 that works out the cheaper per food unit that is the ])est for the stock 



