MANURIAL VALUE 189 



In the absence of definite knowledge of the con- 

 stitution of the proteins of most fodders the safe 

 course is to recommend a mixed ration. 



Having framed such a mixed ration the next 

 step is to decide in what quantity it is to be used. 

 At first sight it might appear that foods should be 

 used in proportion to the number of food units 

 they contain, but a little consideration shows that 

 food units are not a measure of nutritive value, 

 for in calculating them the factor for reducing pro- 

 tein to its carbohydrate equivalent was avowedly 

 based on market prices which are certainly not 

 related to nutritive value. 



The market price of protein is high because 

 protein contains nitrogen and phosphorus which 

 have manurial as well as nutritive value. The 

 protein repairs the animal's tissues but is not re- 

 tained permanently in the body. Nearly the whole 

 of its nitrogen and phosphorus is excreted and 

 raises the value of the farm-yard manure produced 

 by the stock. The manurial value is a consider- 

 able item in the market price. In the case of lin- 

 seed cake costing before the war .9 per ton the 

 manurial value was assessed at about {2 per ton. 

 Manurial value is not related directly to nutritive 

 value and, being included in the calculation of food 

 units, food units cannot be used as a guide in ar- 

 ranging a ration. 



For arranging rations it was necessary to con- 

 sider two points : the relative proportion of protein 



