

MiolUDY OFORATIONS FED TO MILCH COWS. 43 
Table 12, on pages 4o to 42, gives a summary of twenty-five 
rations fed on dairy farms in Connecticut. In the first five 
columns are given the total nutrients and the total fuel value in 
the materials fed. The three following columns give the calcu- 
lated weights of digestible protein, fats and carbohydrates. As 
explained on page 30, these weights are calculated from the 
total nutrients by the use of factors (digestion coefficients) 
obtained from digestion experiments. These factors are only 
approximate, and the weights of nutrients obtained by their use 
are also approximate. The next column contains the nutritive 
ratio and the last column gives the fuel value of the digestible 
nutrients in the rations. 
It will be seen from table 12 that the smallest weight of digest- 
ible protein fed per day per 1,000 pounds live weight, was 1.35 
pounds, and the largest amount was 3.48 pounds. The fuel 
value of the digestible nutrients fed per 1,000 pounds live weight, 
varied from a minimum of 28,600 Calories to a maximum of 
42,600 Calories. ‘There was also a correspondingly large range 
in the nutritive ratio of the rations fed. The narrowest ration 
Meuscie ratio Of 1:4.5; the widest, of 1: 11.3. 
EXPLANATIONS. 
Uses of food.—The two chief uses of food are to form the 
materials of the body and make up its wastes, and to yield energy 
in the form of heat to keep the body warm and in the form of 
muscular and other power for the work it has to do. ‘The prin- 
cipal tissue-formers of the food are the protein or nitrogenous 
compounds. They build up and repair the nitrogenous mate- 
tials, as the muscle and bone, and supply the albuminoids of 
blood, milk, and other fluids, ‘The chief fuel ingredients of the 
food are the carbohydrates (such as sugar, starch, etc.,) and fat. 
These are either consumed in the body or stored as fat to be’ 
used as occasion demands. 
Fuel value.—The value of food as fuel may be measured in 
terms of potential energy. The unit commonly used is the 
Calorie. One Calorie is the amount of heat necessary to raise 
the temperature of a pound of water about four degrees Faren- 
heit.* From experiment it has been found that a pound of pro- 
tein or carbohydrates yields, when burned, about 1,860 Calories 
of fuel value and that a pound of fat yields about 4,220 Calories. 

* The Calorie is exactly the heat necessary to raise the temperature of 1 kilogram of water 
one degree Centigrade. 
