16 



FEEDING VALUE OF CEREALS. 



COMPARATIVE NUTRITIVE VALUE AND NUTRITIVE RATIO. 



According to the figures given by Rubner for the metabolizable 

 energy of the nutrients of food, protein and starch have an equal 

 value, namely, 1,860 Calories, while the ether extract has 2.25 times 

 as much, namely, 4,220 Calories. This relation has led to the use of 

 two factors for valuation based directly jm the amount of digestible 

 nutrients present. If the amount of ether extract is multiplied by 

 2.25 it is then measured on the same scale as the other nutrients and 

 the sum of the amounts of all the nutrients is therefore directly com- 

 parable, one food with another. The total amount of nutrients so 

 found is known as the comparative nutritive value; that is, com- 

 parative nutritive, value = protein + carbohydrate-!- (ether extract 

 X2.25). The figures thus obtained express the relative value of 

 foods measured by the amount of digestible nutrients present. 



Another factor based on these facts is the nutritive ratio which 

 expresses the relative amounts, in a food, of the two classes of nutri- 

 ents, namely, the heat-producing nutrients and those producing flesh 

 or tissue. The proteins of a food are the constituents which build up 

 the tissue of the animal and are productive of muscular energy. The 

 carbohydrates and fats, on the other hand, are chiefly heat or fat 

 producers. The ratio between these two groups has been long con- 

 sidered as of value in indicating the general character of the food as 

 fattening and heat producing or as productive of increased muscular 

 tissue and energy. 



This ratio, "protein : (carbohydrates + ether extract X 2. 25) :: l:z," 

 is termed " broad" when it is :: 1 : 8-12 as in maize and indicates a 

 predominance of heating or fattening elements; and it is termed 

 "narrow" when it is :: 1 : 4-7, as in oats, hi which the constituents 

 producing muscular tissue are in excess. The comparative nutritive 

 value and the nutritive ratio of these grains, which have been dis- 

 cussed in the preceding tables, are shown in Table IX. 



TABLE IX. Comparative nutritive value and nutritive ratio of grains. 



Table IX shows clearly the significance of the term "nutritive 

 ratio" as exemplified by the two characteristically different grains 

 maize and oats, the former being a heat-producing food with a ratio 

 1 : 12.3, and the latter a tissue-forming food whose ratio is 1: 5.8. 



