EXPERIMENT STATION BULLETINS. 253 



Chemical examination has shown that protein contains on the average 

 about 16 per cent of the element nitrogen, and that protein compounds 

 are quite uniform in this respect. Because of this fact the protein com- 

 pounds of cattle feeding stuffs are called not infrequently nitrogenous 

 compounds. 



Fat. — The meaning of the word fat in relation to cattle feeding is the 

 same as when used in ordinary conversation. The fat found by the chem- 

 ist to exist in clover hay, corn meal, and other feeding stuffs is very 

 similar in composition to animal fat like lard, butter fat or tallow. 

 The quantity of fat existing in the various feeding stuffs varies within 

 very wide limits. Of the total weight of the seeds of the flax and the cot- 

 ton plants fully one quarter is oil, while mangolds, straw and green fod- 

 ders contain relatively little fat. The fact that nearly all of our fodders 

 do contain fat is the one which it is important to remember. 



Carbohydrates. — Both protein and fat are essential constituents of the 

 diet of mankind. But not a single meal would be deemed complete in 

 this latitude if it consisted wholly of a combination of these two nutri- 

 ents. The appetite calls for some starchy food. This is usually supplied 

 by potatoes or some other vegetable. Boiled potatoes are composed of 

 approximately the following constituents in the proportions, indicated: 

 water, 73.7 per cent; protein, 2.7 per cent; fat, .2 per cent; and starch 

 22.3 per cent. Honey and syrups are composed almost entirely of sugar. 

 In the animal economy it has been pretty clearly shown that the sugar 

 and starch serve as a source of energy. For reasons that need not be 

 discussed here the chemists have used the term carbohydrates as the 

 name of the class of nutrients which includes both starch and sugar. 



In cattle feeding the materials with which we have to deal contain a 

 large proportion of fibrous material. These woody matters are digested 

 to some extent in the intestines of the cow. The chemist distinguishes 

 between the crude fiber of the forage crops and the more soluble starch 

 and sugar and similar compounds. The former he calls crude fiber, and 

 the latter, nitrogen-free extract because containing no nitrogen. As far 

 as digested, however, all of these materials are equivalent to starch, and 

 in the following discussions the digestible crude fiber will be reckoned 

 under the general term of carbohydrates. In the human diet the potato 

 stands well up in the list of the articles furnishing the most carbo- 

 hydrates since it contains, when boiled, 22.3 per cent of starch and other 

 carbohydrates. Other vegetables are also relatively rich in starch, sugar 

 and woody fiber all of which are carbohydrates. In cattle foods our com- 

 mon field-cured fodder corn contains per hundred weight, 36.5 pounds of 

 the soluble carbohydrates, called by the chemist nitrogen-free extract, 

 and 22.1 pounds of the less soluble but still partly digestible crude fiber, 

 both are, of course, carbohydrates. 



Carbohydrates make up the bulk of the stems and leaves of our forage 

 crops and are the principal constituents of our grain feeds as well. 



Ash. — The ashes remaining when a feeding stuff is burned have a cer- 

 tain part to play in the nutrition of animals. While there is usually no 

 lack in ordinary feeding of this constituent of fodder, sometimes in the 

 case of young animals fed very largely on grain as in the case of pigs fed 

 on corn, the lack of the ash element shows itself in the weak bony struc- 

 ture of the animal and in a general lack of thrift. 



