MANUAL OP CATTLE-FEEDING- 53 



pound for pound ; but the fat produces a greater effect in 

 the body than an equal weight of carbhydrates, and this 

 fact must be taken into account. It was formerly believed 

 that the non-nitrogenous nutrients served chiefly as fuel in 

 the body to maintain the animal lieat, and that since a 

 pound of fat yields two and one-lialf times as much lieat 

 when burned as a pound of starch, it was therefore two 

 and one-half times as valuable a food, and hence, in calcu- 

 lating nutritive ratios, the fat was reduced to its " starch 

 equivalent " by multiplication by 2|-. We now know tliat 

 this is but a partial and, for purposes of feeding, a mis- 

 leading view, and it is probable that in time the present 

 factor, 2|-, will be replaced by a more correct one ; but tliat 

 time is not yet, and^ in the meantime, we must follow 

 established custx>m, for the sake of 3iendering our analy^ 

 comparftHe wi& others. 

 We therefore make the following calculation: 



Digestible fat x 3| = 3.0 



Digestible fibre , =15 



Digestible extract =^5 8 



Digestible protein =5.4 



The nutritive ratio, then, is 5.4 : 43.8, or 1 : 8.1 ; tlie 

 quantity of digestible protein beiiig usually taj^a as 

 unity. 



