120 PASTORAL AND AGRICULTURAL BOTANY 



proportion of digestible protein contained in comparison with the other 

 nutrients, so that by nutritive ratio is meant the ratio which exists in 

 any given feeding stuff between the digestible crude protein and the com- 

 bined digestible carbohydrates and fat. The nutritive ratios for dent 

 corn is determined as follows: The digestible fat in 100 pounds of dent 

 corn is 4.6 pounds, which is multiplied by 2.25, because fat will produce 

 2.25 times as much heat on being burned in the body as do the carbo- 

 hydrates. Add the product to 67.8 pounds, the digestible carbohydrate, 

 which gives 78.15 and divided by the amount of digestible crude protein 

 7.5, which gives as a-quotient 10.4, which is the second factor of the ratio. 

 The colon is used to express the nutritive ratios thus i : 10.4, which is 

 read as follows: for each pound of digestible crude protein i dent corn 

 there are 10.4 pounds of digestible carbohydrates, or fat equivalent. It 

 follows from the above that a narrow nutritive ratio is one having much 

 crude protein in proportion to carbohydrates and fat combined. A wide 

 ratio is where the percentage of crude protein is small compared to the 

 carbohydrates and fats. Linseed meal rich in protein has the narrow ratio 

 of i : 1.6; oats i : 6.3, while oat straw has the wide ratio of i : 44.6, because 

 of its low content of crude digestible protein. Carbonaceous feeds are 

 those with a wide nutritive ratio. Nitrogenous feeds are those with a 

 narrow nutritive ratio. 



Energy of Food. The energy of the animal body is derived from the 

 food which serves as the fuel in supplying that energy. The full value of 

 a feeding stuff is ascertained by burning a weighed quantity of it in pure 

 oxygen gas under pressure in an apparatus called a calorimeter. The 

 evolved heat is taken up by water surrounding the burning chamber and 

 is measured with a thermometer, the units of measurement being the calorie 

 and the therm. A calorie is the amount of heat required to raise the tem- 

 perature of i kilogram of water iC. or i pound of water nearly 4F., A. 

 therm is 1,000 Calories, or the amount of heat required to raise 1,000 kilo- 

 grams of water iC. or 1,000 pounds of water nearly 4F. 

 The full value of 100 pounds of 



Anthracite coal 358-3 Therms 



Timothy hay with 15 pc moisture I75-I Therms 



Pure digestible protein 263.1 Therms 



Pure digestible carbohydrates 186.0 Therms 



Pure digestible fat 422.0 Therms 



