1894.] PUBLIC DOCUMENT — No. 33. 147 



What the Excreta of an Animal is. 



The fa3ces are nothing more than the undigested portion 

 of the food. It is the portion that has resisted the action 

 of the various secretions of the stomacli and digestive fluids 

 and bacteria of the intestines, and is consequently excreted 

 by the animal as so much worthless material. The urine is 

 entirely distinct from the freces. It contains the water, and 

 the end products of the digestion of the nitrogenous portion 

 of the food, — the urea and hippuric acid, — which have 

 been removed from the blood by the kidneys. It also con- 

 tains about one-third of the phosphoric acid and nearly all 

 of the alkalies of the food consumed that have not been 

 retained in the animal's system, and small quantities of other 

 materials that it is unnecessary to consider in this connection. 



How the Digestible Matter of a Food is Determined. 



First ascertain the amount and composition of the food 

 consumed by an animal in a given length of time, also the 

 amount and composition of the fteces or undigested portion 

 excreted in the same time on the basis of dry matter. The 

 difference between them will represent the amount of the 

 various constituents of the food digested. 



The percentages of the constituents digested are called the 

 dio:estion coefficients. 



DESCRIPTION OF THE PRESENT EXPERIMENT. 



It has been found that ruminants — cows, steers, sheep, 

 etc, — digest very nearly equal quantities of the same foods.* 

 Sheep being easier to work with, the experiments here re- 

 ported were conducted with these animals. The animals 

 were grade Southdown wethers. Nos. I. and II. were three- 

 year-olds, and Nos. III. and IV. yearlings. They weighed 

 about one hundred pounds each. 



* See exception to this in Pennsylvania Station Report, page 46, 1890. This 

 experiment showed that sheep digested fourteen to fifteen per cent, less dry matter, 

 cellulose and nitrogen-free extract matter, and only one-half as much protein, as dii/ 

 steers, in case of ensilage made from Burrell and Whitman corn. 



