Animal nutrition / [Thomas Barlow Wood].

  • Wood, T. B. (Thomas Barlow), 1869-1929
Date:
1924
Catalogue details

Licence: In copyright

Credit: Animal nutrition / [Thomas Barlow Wood]. Source: Wellcome Collection.

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    when completely oxidised gives out 4,100 calories: 1 gm. of fat, 9,300 calories; 1 gm. of protein, 5,800. Digestible carbohydrates, however, before they are absorbed from the alimentary canal, are attacked by bacteria which, on the average, take a toll of about 8 per cent., which they trans¬ form into marsh gas, a combustible product which leaves the body unoxidised. Proteins, again, are not completely oxidised by the animal, but leave the body in the urine, in the form of urea, uric acid, and other similar products which are still capable of further oxidation, and, therefore, still contain a proportion of the heat of the protein. Fats, as estimated in feeding stuffs by extraction with ether, are not quite pure, since ether dissolves small quantities of other materials. These impurities have a lower heat value than pure fats. These facts are tabulated below :— Gross and Net Heat Values of Food Constituents. Heat of Deductions—calories. Net Heat Value to Combustion per gm. calories. Marsh Gas Fermenta¬ tion. calories left in Urea, Uric Acid, etc. Lower Heat Value of Impurities. Animal, calories per gm. Protein ... 5800 1100 4700 Fat . 9300 o o o 8800 Carbohy¬ drates .. 4100 340 3700 These figures show that from 1 gm. of protein an animal obtains 4,700 calories; from 1 gm. of fat, 8,800 calories, and from 1 gm. of of carbohydrates, 3,760 calories. The relative heat-producing values, taking that of starch as 1, are, for protein, or 125, and for fats, §f|g, or 2 3. Using these relative heat-producing values, it is possible to calculate the amount of starch which would be required to