THE FEEDING OF THE ANIMAL 249 



one -half pounds of digestible heat and fat- 

 forming elements. A ratio is said to be wide or 

 narrow when the proportion of heat -forming 

 nutrients is large or small in proportion to the 

 protein. Thus, 1: 12 is wider than 1:7. 



454. A certain proportion should exist between 

 the nitrogenous and non- nitrogenous nutrients of 

 a ration. Animals that are growing rapidly, that 

 are bearing young, and that are producing wool, 

 milk or eggs, require a more nitrogenous food 

 than animals that are working, or fattening, or 

 living without gain or loss of weight. For the 

 latter, the nutritive ratio may be as wide as 1: 12 

 or 1 : 14 ; for the former, the nutritive ratio should 

 be as narrow as 1:5 or 1:6. 



455. Formerly it was supposed that slightly 

 differing nutritive ratios would make distinct 

 differences in the effectiveness of a ration or the 

 quality of the product ; but it is now generally 

 considered that the limits of variation in the 

 nutritive ratio may be rather wide without mate- 

 rially influencing the nutritive effect of the 

 ration. Other conditions may mask the effect 

 due to differences in the nutritive ratio. 



456. One of the chief reasons for taking the 

 nutritive ratio into consideration is that the pro- 

 tein may be economically used. Protein should 

 be used for the formation of nitrogenous products 

 in the animal. It may, however, be used as a 



