FEEDS AND FEEDING. 49 



The digestible fiber is generally added to the digesti- 

 ble nitrogen free extract and called digestible carbo- 

 hydrates. In this case, then, the total digestible car- 

 bohydrates would be 65.5 -f- 1.3 = 66.8 Ibs. As 

 mentioned previously the water is not considered a 

 nutrient as it can be supplied so much cheaper by 

 itself. The ash is also omitted because most of our 

 feeds contain enough of this substance for the needs 

 of the animal. 



Necessity of Composition and Digestibility. There 

 are several feeds which have practically the same chem- 

 ical composition but different percentages of digesti- 

 bility. Then in order to ascertain the real value of 

 any feed it is necessary to know the chemical compo- 

 sition and the digestibility. 



Nutritive Ratio. The ratio between the digestible 

 protein and the digestible carbohydrates -f- the di- 

 gestible fats is called the nutritive ratio. This ratio 

 is obtained in the following manner. The per cent, of 

 digestible fat is multiplied by 2.25, to reduce it to 

 terms of carbohydrates. (It was previously stated in 

 Section LXI, that the fuel value of fat is 2.25 times 

 that of carbohydrates.) This product is then added 

 to the per cent, of digestible carbohydrates. This sum 

 is divided by the per cent, of digestible protein. To 

 explain this more clearly let us take the digestibility of 

 corn, as just cited in the article under digestibility of 

 feeds. 



Digestible fat (4.3) X fuel value (2.25) = carbohydrate equivalent (9.7). 

 Digestible carbohydrates (66.8) + 9.7 = Total digestible carbohydrates 



(76.5). 



Total digestible carbohydrates (76.5) H- digestible protein (7.8) = 9.8. 

 Nutritive ratio is then i :g.8 



EXERCISE. What is the per cent, digestibility of the ingredients of 

 wheat bran ? The composition and the digestibility of this feed are 

 given in table No. I. What is the nutritive ratio of a feed containing 

 T2.6 per cent, digestible protein, 20 per cent, digestible carbohydrates 

 and 5.2 per cent, digestible fat? If a horse is fed 7 pounds of corn 

 and cob meal a day, how many pounds of protein, fat and carbo- 

 hydrates does it digest? 



