190 THE CHEMISTRY OF THE FARM 



seen that certain kinds of food may be used for 

 maintenance which are quite inappropriate for the 

 production of increase. The relative values of various 

 cattle foods for the production of increase have been 

 given in the table on p. 160. We have also partly 

 discussed the composition and amount of the increase 

 obtained when an excess of food is supplied over that 

 needed for maintenance. We have seen (p. 127) that 

 100 parts of starch may yield in the ox 23*3 of fat ; we 

 may say, therefore, that, in round numbers, 4 of starch, 

 or its equivalent in other food constituents, can produce 

 about 1 of pure fat. 



The increase in live weight actually obtained when 

 animals are fattening contains, on an average, accord- 

 ing to Lawes and Gilbert's estimate, 66 per cent, of 

 fat, the rest being nitrogenous matter, water, and ash 

 constituents (p. 110). If we calculate the calorific 

 value of this increase by means of the factors given 

 on p. 119, we find that 1 gram has the value of 6'64 

 Calories. As 1 gram of starch has a production value 

 for the ox of 2*2 Calories, it appears that 3 of starch, or 

 its equivalent in other food constituents, should pro- 

 duce 1 of fattening increase. The production values of 

 different cattle foods have been given in the table 

 on p. 160 in terms of starch ; it is easy, therefore, to 

 calculate what amount of fattening increase each food 

 is capable of producing. Thus we see that 1*36 lbs. 

 of linseed cake is equivalent to 1 lb. of starch; it 

 follows, therefore, that 1*36 x 3 = 4*08 lbs. of linseed 

 cake can produce 1 lb. of fattening increase. In the 

 same way we find that about 9 lbs. of average meadow 

 hay, 15 lbs. of potatoes, and 30 lbs. of small mangels, 

 can also produce 1 lb. of increase in live weight when 



