THE NUTRITION OF THE HORSE. 245 



The above results and others that could be cited were based largely 

 upon digestible nutrients in the foods fed and their relation to work per- 

 formed, and did not take into consideration the energy expended in digest- 

 ing the different kinds of feeds resulting in the loss of varying amounts 

 of heat, nor the heat radiation resulting from the increased metabolism 

 caused by certain feedstuffs. 



B. Recent Investigations and the Application of Calorimetky. 



The development and application of calorimetry, and its use in studying 

 the intake and outgo of energy, has proved of great help in increasing our 

 knowledge of the principles of nutrition and the nutritive value of animal 

 feeds. The following calorimetric units and methods are employed in 

 measuring the utilization of energy: — 



(a) The Calorie. — The heat which is given off by a food when combined 

 with or burned in oxygen is the measure of its total energy. The unit of 

 energy is termed the calorie, and represents the amount of heat required 

 to raise 1 kilogram of water 1° C. (Armsby has recently introduced the 

 term therm, or larger unit, meaning the amount of heat necessary to raise 

 1,000 kilograms of water 1° C.) According to Stohman, Berthelot and 

 Riibner the heat units, or number of calories, in 1 gram of protein or car- 

 bohydrates are 4.1, and in fat, 9.3, and the total energy of a food is the 

 amounts of protein and carbohydrates multiplied by 4.1, and of fat mul- 

 tiplied by 9.3. 



(6) The Kilogrammeter. — This represents the mechanical equivalent of 

 a definite amount of heat, and is equal to the energy required to raise 1 

 kilogram of water 1 meter high. 



A calorie of heat is equivalent in mechanical energy to that requked to 

 raise 427 kilograms 1 meter high (or 427 kilogrammeters), and this unit 

 is called kilogram-calorie. 



To convert digestible protein, carbohydrates and fat into kilogram- 

 meters, multiply the grams of protein or carbohydrates by 4.1, and the 

 fat by 9.3, and these products by 427. 



(c) The Respiratory Quotient. — The relation of the oxygen consumed 

 to the carbon dioxide given off has been termed by Pfliiger the respiratory 

 quotient, and is determined by dividing the volume of the carbon dioxide 

 by the volume of oxygen. 



In case of carbohydrates, glycogen, starch and sugar, the coefficient is 

 equal to 1; in case of albuminoids, .729; ^ of fat, .700; and of alcohol, .666. 



An animal in a state of repose consumes a definite amount of oxygen 

 in the breaking up or burning of the food, and gives off a definite amount 

 of carbon dioxide, the jneasurement of which forms a basis for the food 

 required for maintenance. The consumption of oxygen and the exhala- 

 tion of carbon dioxide are rapidly increased the moment any work is per- 

 formed. This method has been used with the horse by introducing tubes 



» After Lavalard, already cited, p. 123; according to Kellner, p. 75, .765. 



