52 MANUAL OF FARM ANIMALS 



common foods. It is not now considered necessary to balance 

 rations with the mathematical exactness that was formerly in 

 vogue. Yet it must conform in a general way to the standard. 

 A great number of experiments demonstrate conclusively the 

 practicability of feeding the balanced ration. Balancing ra- 

 tions is, however, a tedious undertaking, as there is no mathe- 

 matical formula, and one must add to or take from his trial 

 ration until the desired standard is obtained. 



Nutritive-ratio. — The nutritive-ratio is the proportion between 

 the digestible protein in a given food and the digestible carbo- 

 hydrates and fats. It is ascertained in the following manner: 

 Multiply the digestible fat by 2j, add the product to the 

 digestible carbohydrates, and divide their sum by the digestible 

 protein. 



The method of calculating the nutritive-ratio of corn, the diges- 

 tible nutrients of which are protein 7.9, carbohydrates 66.7, and 

 fat 4.3, is as follows : — 



This gives a nutritive-ratio of 1 : 9.6 for corn, and it means that 

 for each pound of digestible protein in the corn there are 9.6 

 pounds of digestible carbohydrate and fat equivalent. A 

 nutritive-ratio may be distinguished as "narrow" or "wide." 

 A narrow ration is one in which the proportion of protein is 

 quite large, say 1 : 4.5, whereas a wide ration is one where the 

 carbohydrates are large, say 1 : 8 or 1 : 10. These terms do not 

 represent exact values, but are used in a general way. 



To illustrate the method of calculating a ration for a given 



