Digestion — Respiratio n — Calorimetry — En e rgy . 41 



similar manner the other digestion coefficients for malt sprouts are 

 determined. The table reports 104,6 per ct. of the fat of malt 

 sprouts digested — an absurdity. The total quantity of fat in the 

 feeds used in this trial was so small that an error like this could 

 easily occur. 



Table II of the Appendix shows the coefficients of digestibility 

 of American feeding stuffs so far as they have been ascertained. 



60. Concerning digestibility. — In digestion trials it is assumed 

 that all matter appearing in the so-called solid excrement has 

 escaped the action of the digestive ferments, and so represents the 

 indigestible part of the food. Tho correct in general, there are 

 exceptions to this assumption. Solid excrement contains some 

 waste from the body itself, such as bile residues and matter which 

 sloughs off from the walls of the alimentary tract. Since these 

 wastes cannot be wholly separated and determined, they tend to 

 vitiate the accuracy of digestion studies. 



Armsby has shown^ that ruminants feeding on coarse forage con- 

 vert much of the fiber into marsh gas, or methane, wiiieh has no 

 nutritive value. In such cases digestion trials will show too high 

 a value for the fiber. 



In digestion studies the so-called fat is determined by the use of 

 ether, which not only dissolves the true fat, but also chlorophyll, 

 wax, bile residues, and other substances which are not true fat. 

 Due to this, and because the fats in feeding stuffs are usually in 

 relatively small amount, errors are liable to occur in their deter- 

 mination. The true fats are highly digestible. 



Table II of the Appendix shows that feeds low in fiber and rich 

 in nitrogen-free extract usually have a high factor of digestibility; 

 for example, corn, barley, linseed meal, etc., are better digested than 

 straw, chaff, etc. The percentage of digestibility of the grasses 

 decreases as they approach maturity. However, the large accumu- 

 lation of starch which occurs in the corn plant, a grass, as it ripens 

 gives the more mature form a greater total feeding value. (18) It 

 seems reasonable that palatability should stimulate the supply of 

 digestive fluids, as it must likewise stimulate the action of the di- 

 gestive tract itself. 



Grinding grain to meal may or may not increase its digestibility. 

 Jordan- states that crushing or grinding grain for horses may in- 

 crease its digestibility as much as 14 per ct. Cooking food usually 



' Cyclopedia Am. Agr., ill, p. 65. ^ The Feeding of Animals, p. 133. 



