XI.] VALUATION OF FEEDING STUFFS 213 



For example, the factor for meadow hay is about 70 per 

 cent, which means that the digestible protein in the 

 meadow hay, instead of being capable of yielding 23 per 

 cent, of its weight of fat stored up in the animal (suppos- 

 ing the hay is added to the diet required for maintenance 

 so that it can all be utilised for making increase), will 

 only yield 70 per cent of its full value of 23 per cent., i.e. 

 the digestible protein of the meadow hay will only be 

 converted into 16 per cent of its weight of stored up 

 fat In the calculations in the preceding chapter 

 (P- 193) we deducted 3 per cent, of the energy con- 

 tained in the digested part of cotton cake, but 40 per 

 cent, of the energy contained in digested meadow hay, 

 in order to find the dynamic energy available for work 

 or increase. 



We can make use of the values which have been 

 deduced for the digestible constituents in the feeding 

 stuffs so as to obtain a single figure which sums up the 

 relative value of the feeding stuff. We have already 

 attempted to do this in a somewhat imperfect fashion 

 when discussing the analysis of the feeding stuffs. We 

 have taken as a kind of guide the fact that the fats are 

 about two and a quarter times as valuable for fuel 

 purposes as the carbohydrates, and have also made the 

 assumption that the proteins are worth about as much 

 as fats (a commercial assumption which takes into 

 account the value of its nitrogen as well as the fuel 

 value of the protein). Thus, we can add to the per- 

 centages of carbohydrates the percentages of fat and 

 protein multiplied by 2-3, and so obtain the number of 

 units which represent the value of the food in terms of 

 carbohydrates. Such a valuation, which is all or more 

 than the market takes account of, possesses little exact 

 value, because it neglects the digestibility of the various 

 constituents. But if we base our calculations upon the 



