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PART I. AGRICULTURE.

I. FEEDING STUFFS.

COMPOSITION OF FEEDING STUFFS.

In the ordinary chemical analysis of feeding stuffs the following constituents are determined, viz., water, ash, protein, crude fiber, nitrogen-free'extract, ether extract (fat).

Water is present in all feeding stuffs, from above 90 per cent in green foods and some kinds of roots, to below 10 per cent in very dry hay and in concentrated food stuffs.

Ash, or mineral matter, is the non-combustible part of plants, and goes to make the bones of the animal, or to supply material for the maintenance of other parts of the animal body.

Protein is the name of a large group of substances, all characterized by the fact that they contain the element nitrogen; hence they are also called nitrogenous substances, and foods rich in protein are spoken of as nitrogenous foods. The protein substances supply the material necessary for the formation of lean meat, ligaments, tendons, hair, horns, hoofs, etc., and also of casein of the milk. Crude protein includes albuminoids and amides; among the former are found white of egg, lean meat, curd of milk, and gluten; among the latter, asparagin and other crystallizable and water-soluble substances, generally speaking, of a somewhat inferior nutritive value.

Crude Fiber or woody fiber is the framework of plants, forming the walls of their cells; it is usually the least digestible portion of feeding stuffs, and the nutritive value of a plant is decreased as its crude fiber content increases.

Nitrogen-free Extract includes starch, sugar, gums, organic acids, etc., and forms a most important and usually a very large part of cattle foods. Together with cellulose, nitrogen-free extract forms the group of bodies called carbo

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hydrates. A general name for carbohydrates is heat-producing substances, as against flesh-forming substances, i.e., nitrogenous compounds, the names indicating the main offices of the substances in animal nutrition.

Ether Extract, or crude fat (oil) includes a group of compounds dissolved out by ether in the analysis of foods; fat forms the main part of the extract; most feeding stuffs contain only a small quantity of fat, but this component is nevertheless of considerable importance in the feeding of animals.

Organic Matter signifies the combustible portion of chemically dry feeding stuffs, i.e., all the components given in the preceding except water and ash.

Digestible Components.-The food stuffs used in the feeding of farm animals are only partly of direct value to the animals, the portion which their digestive fluids are unable to dissolve being voided in the excrements. The digestibility of fodders has been determined by direct experiments with different kinds of farm animals, in this country or abroad. The digestion coefficients (see pp. 6–8) mean the percentages of any one component which have been found to be digested by the animals experimented on.

Nutritive Ratio signifies the ratio between the digestible nitrogenous and non-nitrogenous components in a feeding stuff, or a combination of such. As fat has been found to yield about 2.2 times more heat, when burned, than do starch, sugar, and other carbohydrates, the per cent of digestible fat in a food is multiplied by 2.2 when the nutritive ratio is to be calculated; the product is added to the per cent of digestible carbohydrates (nitrogen-free extract + crude fiber), and this sum is divided by the per cent of digestible protein. (The factor 2 or 2 is sometimes used for obtaining "the starch equivalent" of fat.)

Example: Clover hay contains on the average 6.5 per cent digestible protein, 34.9 per cent digestible carbohydrates, and 1.6 per cent digestible fat (see following table):

1.6 X 2.2 = 3.52;

34.9 +3.52 = 38.42; 38.42 ÷ 6.5 = 5.9. Nutritive ratio, I : 5.9,

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* Largely from Jenkins and Winton's Compilation of Analyses of American Feeding Stuffs.

+ König.

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