82 A STUDY OF FARM ANIMALS 



express the ratio of the digestible protein to the digestible 

 non-protein substances in the food, or the combined car- 

 bohydrates and fat to the protein. In order to compare 

 these substances on an equal basis, they are reduced to the 

 same heat valuation. Protein and the carbohydrates do have 

 the same heat value, but a pound of fat is equivalent to 

 about 2)4 pounds of either one of these. Consequently the 

 chemist, in order to place them on an equal footing in heat 

 value, multiplies the digestible fat by 2J^. The nutritive 

 ratio is found by adding this to the amount of the carbo- 

 hydrates, and then dividing the sum by the digestible pro- 

 tein content. The following example will illustrate the 

 method of finding the nutritive ratio: 



Oats contain 10.7 pounds of digestible protein, 50.3 

 pounds carbohydrates and 3.8 pounds fat. Then the ratio 

 is worked out in this manner. 3.8 pounds fat x 2 l /i = 8.55 

 = the carbohydrate equivalent of the fat. 

 50.3+8.55 -58.85 

 10.7) 58.85 ( 5.5 

 53.5 



535 

 535 



Nutritive ratio, 1 : 5.5 



The nutritive ratio is obtained in the same way for an 

 entire ration, dividing the total amount of the digestible 

 carbohydrates and fat by the total digestible protein. A 

 nutritive ratio of 1 : 5.5 means that for each pound of digesti- 

 ble protein to be found in the ration there are 5.5 pounds 

 of carbohydrates or its equivalent. 



A narrow nutritive ratio is one in which the amount of 

 carbohydrates and fat is not large in proportion to protein, 

 such as 1 : 3, or 1:5; a moderate amount would be 1 : 8; while 

 a wide ratio would be 1:12. Highly concentrated foods, such 

 as tankage or oil meal, usually have narrow ratios; while 

 coarse foods, like the common roughages, of which corn 

 stover or timothy hay are good examples, have wide ratios. 



