Feeding Standards. 237 



Other investigators have found that the Wolff allowances may be 

 too high. Haecker of the Minnesota Station maintained a dry. 

 barren cow of a 1000 pounds weight on 0.6 pound of digestible 

 protein, 6 pounds of digestible carbohydrates, and 0.1 pound of 

 digestible fat (ether extract). 



Energy value of feeds. The function of food, as has already 

 ' been pointed out, is not only to repair waste and promote growth 

 and increase, but also to furnish heat and energy. For this 

 reason, attempts have been made by several investigators to assess 

 the relative value of feeds by a determination of their heat pro- 

 ducing power. Heat units are expressed either in starch equiv- 

 alents or calories. The German investigators, Kellner and Zuntz, 

 have used starch as the basis for expression, while Armsby of 

 this country is using the calorie. The calorie represents the 

 quantity of heat required to raise the temperature of one gram 

 of water from to 1 C. A large Calorie, one thousand times 

 larger than the small calorie, is usually employed for the ex- 

 pression of large quantities of heat and will be used here, gen- 

 erally. However, the new term, therm, which represents 1000 

 large Calories, is now in use by Armsby and is the quantity of 

 heat required to raise the temperature of 1000 kilograms of 

 water 1 C. 



The value in large Calories of one gram of the several classes 

 of nutrients, is given in the following table : 



Wheat gluten 5.8 



Animal muscle 5.7 



Starch.. 4.1 



Cellulose 4.1 



Cane sugar ^ . 



Animalfat.. 9.4 



Available energy. The data in the above table is secured by 

 complete combustion of the material in the calorimeter. Such 

 does not obtain in the animal body. It should be remembered 

 that only part is digested, and as only the digested portion fur- 

 nishes available energy, the available fuel value of a ration must 

 depend primarily upon the amount which is dissolved out of the 

 digestive tract and passes into the blood. There is fuel waste in 

 the solid excrement of the feces, in the incompletely burned gases 



