. Cyclopedia of farm animals. Domestic animals; Animal products. nrn Fig. 59. StaU used in digestion experiments. and csecum, yielding carbon dioxid, marsh gas, and soluble products of inferior nutritive value, chiefly organic acids. The materials thus dissolved in the digestive tract are often spoken of as digestible nutrients. The undigested part of the feeding- stuffs is rejected in the dung, or solid excrement, which, in herbivorous animals, may be regarded as consisting essentially of the indigestible part of the food, mixed with small amounts of residues of the digestive juices, intestin
. Cyclopedia of farm animals. Domestic animals; Animal products. nrn Fig. 59. StaU used in digestion experiments. and csecum, yielding carbon dioxid, marsh gas, and soluble products of inferior nutritive value, chiefly organic acids. The materials thus dissolved in the digestive tract are often spoken of as digestible nutrients. The undigested part of the feeding- stuffs is rejected in the dung, or solid excrement, which, in herbivorous animals, may be regarded as consisting essentially of the indigestible part of the food, mixed with small amounts of residues of the digestive juices, intestinal mucus, and other waste products of the activity of the digestive organs. If, then, we weigh and analyze the feed and the dung of an animal and compute the number of pounds of ash, proteids, crude fiber, and the like, contained in each, we shall find the amounts smaller in the dung than in the feed. The difference between the two amounts shows in each case how much of that particular substance has been dissolved out of the food and taken up into the body; that is, it shows how'much of that ingredi- ent was digestible. The results are com- monly expressed as percentages of the total amounts fed. Thus in an actual experiment, the feed contained pounds of crude fiber and the dung pounds ; evidently, therefore, pounds were digested. Ac- cordingly, dividing by we find that per cent of the crude fiber was diges- tible. The latter figure is called the per- centage digestibility, or sometimes the digestion coefficient, of the crude fiber, and by the same method similar coefficients may be obtained for all the other ingredients of the feed. Conditions affecting digestion. The digestibility of the several ingredi- ents of feeding-stuffs is found to vary con- siderably under different conditions. Some of these conditions affect digestibility by modifying the character of the material fed, and will be considered later. Others modify, or may be supposed to m
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