134 DAIRY CHEMISTRY 



amount, however, in a ration is unnecessary. After 

 the functions of the body are served, the surplus 

 protein is used for producing heat and energy, and 

 it quite frequently happens that a ration is unneces- 

 sarily expensive because of containing an excess of 

 protein, which is used for the production of heat 

 where cheaper nutrients, as the carbohydrates, would 

 serve the same purpose. Neither is a ration that 

 contains too scant an amount economical, as a full 

 milk flow cannot be maintained on a scant supply of 

 protein. The rational feeding of animals is largely 

 a regulation of the supply in the food of proteids and 

 carbohydrates for milk production and other pur- 

 poses. There are a great many different kinds of 

 proteids in food stuffs. Casein and albumin in milk 

 are proteids ; egg albumin is also a proteid. The 

 glutens of wheat and other grains are among the 

 most common proteids found in food stuffs. 



128. Carbohydrates. — With the exception of fat, 

 all the non-nitrogenous compounds, as sugar, starch, 

 and cellulose, taken collectively, are called carbo- 

 hydrates. By far the largest part of the nutrients 

 in food stuffs are carbohydrates. Those carbo- 

 hydrates which are easily rendered soluble, as sugar 

 and starch, are called the nitrogen-free-extract com- 

 pounds. Carbohydrates are a complex group of 

 substances composed of three elements, — carbon, 

 hydrogen, and oxygen. The chief function of the 

 carbohydrates is to produce heat and energy, and, 

 when properly combined with the proteids, they may 



