they furnish the food or fuel to maintain the hfe of the body. 

 They also are convertible into body fat. The protein, however, 

 (including the ash), is the only group from which the animal can 

 make its flesh or lean meat. In order to form the bones all the 

 groups are used. 



2. Digestibility of Cattle Feeds. 

 The several groups of nutrients above described, which make 

 up the various cattle feeds, are valuable to the animal only in 

 so far as they can be digested and assimilated. The concentrated 

 feeds are considerably more digestible than the coarse fodders, 

 as a single illustration will show. 



In the first and fourth columns is given the composition of 

 average samples of timothy hay and of gluten feed. In the second 

 and fifth columns are shown the percentages of the different 

 groups which are digestible. Thus, of the 6.3 pounds of protein 

 in timothy, 48 per cent are digestible, or 3 pounds; and of the 

 26.2 pounds of protein in 100 pounds of gluten feed, 85 per cent, 

 or 22.3 pounds, are digestible. Excluding the ash, which is not 

 generally taken into account, it is shown that 100 pounds of 

 timothy hay contain about 48 pounds of digestible or actual 

 food material, and 100 pounds of gluten feed, 78 pounds. It is 

 evident, therefore, that the gluten feed is decidedly more valuable 

 as a source of nutrition than the timothy hay. 



3. Method of Measuring the Efficiency of Feeding Stuffs. 



The digestibility of a feed, however, is not the true measurement 

 of its nutritive value, for the reason that some feeds contain more 

 metabolizable or available energy than others. What is termed 

 net energy value, expressed in the form of Calories' or therms,' 



' A large Calorie represents the amount of heat necessary to raise 1 kilogram of water 1 * 



Centigrade. It is the unit of heat measurement. A therm represents the amount of heat 

 required to raise 1,000 kilograms of water 1* Centigrade. 



