THE MAINTENANCE RATION 229 



obtained from the protein nutrients, but it is needed in such 

 amount that to provide all of it in the form of protein would be 

 too expensive and injurious to the cow. The starchy and 

 sugary portions of feeds provide energy and heat most cheaply. 

 The fat or oil of corn, hay or other feeds goes, likewise, to the 

 supply of heat and energy. But since the heating power of a 

 feed nutrient is indicated largely by the percentage amount of 

 carbon in its compound, and fat is so much richer in this ele- 

 ment than starch or sugar, it, fat, has about 2.25 times more 

 heating power than starch. The fat of the animal body is not 

 necessarily made from the fat of plants but oily feeds naturally 

 encourage the laying on of fat. For convenience the purely 

 heat and energy-bearing feeds, such as starch and sugar, are 

 called carbohydrates^ while all fats are grouped by themselves. 



It is customary to classify all needed feed nutrients as pro- 

 tein, carbohydrate and fat. These are the three constituents 

 which we must provide in the cow's winter ration if she is to 

 yield milk in winter as freely as in summer. 



The maintenance ration is the name given to the amount of 

 feed which is required to just sustain the weight of an animal 

 for twenty-four hours. On a perfect maintenance ration an ani- 

 mal will neither gain nor lose weight. The amount of feed needed 

 by large cows is naturally greater than that required for small 

 ones, and that by very active animals greater than for slower mo- 

 tioned ones. Just how much of thei three digestible nutrients, pro- 

 tein, carbohydrates and fats, a cow of 1000 pounds' weight re- 

 quires was studied first in Germany, but the figures obtained there 

 were too high to be accurate under American conditions. . 



The standard now most largely used in this country is the 

 one settled upon by Haecker of the Minnesota Station after 

 many years of careful work and is as follows: Digestible pro- 

 tein 0.7 pounds, digestible carbohydrates Y.O pounds, and diges- 

 tible fat 0.1 pound per 21 hours, for an average cow of 1000 

 pounds, where kept under good practical stable conditions. 



The following table gives the nutrients allowed daily for 

 the maintenance feed for cows of given weights, ranging from 

 800 pounds to 1625 pounds, 1 



^Tinn. Bui. 130. 



