2 BULLETIN 637, U. S. DEPARTMENT OF AGRICULTURE. 



based only on chemical composition is to be taken merely as a guide, 

 to be followed in the light of all the knowledge obtainable about 

 animal nutrition. 



NEW METHOD OF BALANCING RATIONS. 



The method of balancing rations commonly used might well be 

 called the "Cut and Try Method." It is faulty for the reason that 

 it usually necessitates several trials to secure the desired result. By 

 using the method described in these pages, balancing a ration is a 

 simple matter of multiplication and division. 1 



Table I gives the excess protein per pound for different protein 

 feeds when used in rations of various nutritive ratios. To illustrate: 

 A hundred pounds of dried brewer's grains contains 21.5 pounds 

 digestible protein and 44.2 pounds digestible carbohydrates. A 

 ration with a nutritive ratio of 1:4, requires only 11.05 pounds pro- 

 tein to balance 44.2 pounds of carbohydrates. Hence, in such a 

 ration, 100 pounds of this feed contains 21.5—11.05, or 10.45 pounds 

 of excess protein. The excess protein in a single pound is thus 

 0.1045 pound. (See Table I, column headed "Ratio 1 to 4," oppo- 

 site brewer's grains, dried.) In rations having wider ratios the 

 excess protein is proportionally greater. 



Some of the figures in Table I are printed in italics. These repre- 

 sent deficiency instead of excess in protein. Thus, in a ration of 

 ratio 1:4, a pound of rye is deficient in protein by 0.0798 pound, 

 while in a ration of ratio 1 : 10, it has an excess of protein amounting 

 to 0.0279 pound. 



In like manner Table II shows the protein deficiency per pound 

 for various carbohydrate feeds as compared with rations of specified 

 nutritive ratios. The italic figures in this table represent excess 

 protein. Thus, in a ration of ratio 1:4, a pound of buckwheat is 

 deficient in protein by 0.0572 pound, while in a ration with ratio 1 : 10 

 it has an excess of 0.0257 pound of protein. 



1 The tables used in this bulletin are based upon Table in, Digestible nutrients and fertilizing constit- 

 uents, in Henry's " Feeds and Feeding." It was necessary to include the digestible fat, with its equivalent 

 fuel value (2^ Xcarbohydrate) with the carbohydrate in order to prepare the tables. In proposing a mathe- 

 matical method for balancing rations different from the one commonly employed, the same assumptions 

 are made as in the case of the usual method, viz, that fats have two and one-fourth times the feeding 

 value of the carbohydrates and that a pound of carbohydrates or protein has a uniform value whatever its 

 source. The latter assumption is, of course, not strictly true. Proteins differ somewhat in their nutri- 

 tive value, and sugars have nutritive and physiological effects somewhat different from those of starches. 

 Nevertheless, the assumption of the equality of value of these nutritive elements in various feed stuffs 

 introduces a no greater source of error in the method proposed in this bulletin than in the usual method 

 of balancing rations. 



The method of balancing rations described in this bulletin is based on the principle (alligation) proposed 

 by Prof. J. T. WHlard in Kansas Experiment Station Bulletin 115, but the method of applying this 

 principle is different, and is believed to be simpler and more convenient, especially when several feeding 

 stuffs are to be used in the ration. 



