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 



