63 



eluding 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 tim- 

 othy, 48 per cent are digestible, or 3 pounds; and of the 26. 2 pounds 

 of protein in 100 pounds of gluten feed, 85 per ce-nt 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 Eficiency of Feeding Stuffs. 



The digestibility of|a feed, however, is not the true measure- 

 ment of its nutritive value, for the reason that some feeds require 

 more energy for their digestion 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 1000 kilograms ofjwater 1° Centigrade. 



