l8o POULTRY CULTURE 



Nutrient ratio. The relative proportions of principal elements 

 in food articles are mathematically expressed in the form of a ratio, 

 commonly called the nutritive ratio, but more correctly described 

 as the " nutrient ratio." To obtain this the percentage of protein 

 in the article is taken as the first term of the ratio ; the percentage 

 of carbohydrates and fats (the fats being reduced to terms of car- 

 bohydrates)' is taken as the second term, and the ratio is reduced 

 to its simplest form, in which i represents the value of the protein. 

 If the difference in the proportions of the two classes of elements, 

 as thus expressed numerically, is small, the nutritive ration is said 

 to have a narrow ratio ; if the difference is great, the ration is said 

 to have a wide ratio. Rations having a narrow ratio are called 

 narrow rations, and those having a wide ratio, wide rations; but 

 these terms are usually employed to describe the relations of ra- 

 tions compared, not to a standard, but to each other. The chem- 

 ical values of the nutrients in a food are also expressed in figures 

 which represent the total heat-producing value of all elements com- 

 bined; this is called Xhe.ftiel valne or potential energy of the article. 



The chemical composition of any food article may be accurately 

 determined by the chemist, and the nutrient ratio and fuel value 

 established and expressed. As different samples vary in compo- 

 sition, standards for general use are made by taking averages of 

 numbers of analyses of each kind of food. The composition of 

 ordinary lots of whole foods (as grain, hay, milk, and meat of any 

 kind) will closely approximate these standards. The variations from 

 them will not, as a rule, be great enough to materially affect results 

 in feeding, and those who have occasion to calculate percentages 

 may assume that a whole-food article which appears to be of 

 average quality is of average, or standard, chemical composition. 

 Nature makes no variations in foods so great as to disturb the 

 nutritive processes of organisms using them. 



In by-products nutritive values are less stable and uniform. 

 Nearly all states now require such products to be sold under a 

 guaranty of their most valuable nutrients. While this afi^ords the 

 purchaser protection from those who would unscrupulously pass 



1 This is done by multiplying the value of the fats by 2.25 or by 2.27. Author- 

 ities are not all agreed in regard to the fraction, and it makes no material differ- 

 ence, for all values in feeding are approximate and relative. 



