176 CHEMISTRY OF FARM PRACTICE 



Cattle Feeding." The Wolff standard was used unaltered 

 until 1896, when as a result of further experiments, some 

 alterations were made. It was presented annually from 

 1896 to 1906 by Dr. C. Lehman, under the name of the 

 Wolff-Lehmann Standards. Table XVI gives the last of 

 these standards. 



119. Digestible Nutrients. The term digestible nutrient 

 is applied to the digestible portion of feeds. The digestible 

 nutrients are the carbohydrates, the fats and protein. 



The percentage of each feed that is digestible is deter- 

 mined by feeding experiments with various classes of 

 mature animals. Experiments show that ruminants digest 

 the same kind of food about equally well, while horses and 

 swine digest less fiber than do the ruminants ; however, they 

 seem to digest the concentrates about as well as the rumi- 

 nants. Age and breed seem to have no definite influence on 

 digestion. 



120. Metabolism. Metabolism is the process by which 

 digested nutrients are used for the building of tissue and 

 by which these tissues are broken down with the production 

 of heat. The building-up processes are called anabolism, 

 while the breaking-down processes are called catabolism. 



The digested sugars are taken up by the capillaries 

 and carried into the veins, by which they are transferred to 

 the liver, where they are made into glycogen or animal starch 

 and stored temporarily as such. This constitutes the ani- 

 mal's reserve supply of sugar, for it is reconverted into sugars 

 and made use of by the animal as required, especially when 

 work is being done. The fats seem to be absorbed as soaps 

 and glycerin into the intestinal walls, where they are 

 converted into neutral fats and find their way into the 

 circulatory system. The products of the protein digestion 

 are absorbed from the small intestines and converted into 

 serum albumin and serum globulin, which are the nitrogenous 

 materials used in the building of body tissues. All of these 

 materials are transported by the blood to the various 



