6o Journal of Agricultural Research voi. x, no. » 



nished by the rubber markers and which had indicated that the larger 

 or coarser particles of food required a longer time for passage through the 

 animal than the finer particles. 



From the data presented in Table IV we were able to obtain a reliable 

 expression for the average time required for the passage of the food resi- 

 dues through the animal. With the rations used and the quantities fed 

 the time varied from 2.9 to 5.2 days. The two most important factors 

 determining the rate of passage are the nature of the ration and the 

 amount fed. Coarse roughages seem to require a considerably greater 

 time than the more finely ground concentrated feeds, this holding true 

 even when the two kinds of feeds are consumed together, as has been 

 shown in a previous publication.^ As to the influence of quantity, it 

 appears that, when the coarse feeds were fed, a smaller quantity required 

 a greater time for passage of the residues; but, when the feed was a con- 

 centrate in pulverized form, the variation was not so pronounced. Of 

 these two factors the nature of the food seems to be of the greater impor- 

 tance in influencing the rate of passage of the residues through the steer. 



A valuable study might have been made between the rate of passage 

 as ascertained by means of the slaughter tests and the moisture contents 

 of the feces. Such a comparison is not of value with the rations used, 

 since varying quantities of foods were used, and the effect produced on 

 the moisture content of the feces by the quantity of food consumed has 

 not yet been determined. 



In dealing with the influence which the rate of passage of the feed resi- 

 due may have had on the digestion coefficients we are unable definitely to 

 attribute changes to the rate of passage; and at best it can only be said 

 that associated with the more rapid passage there occurred an apparent 

 gain in the digestibility of the ash, negligible results in the case of nitro- 

 gen, a decided loss in the digestibility of the crude fiber, a gain in the case 

 of the nitrogen-free extract, and negligible results in the case of fat. The 

 loss in digestibility of crude fiber was sufficient to overbalance the gains 

 made by the other nutrients, and resulted in a slight decrease in digesti- 

 bility of total dry matter, with a more rapid passage. These findings do 

 not agree entirely with results obtained when the comparisons were made 

 between the digestion coefficients and the m.oisture content of the feces, the 

 greatest variation being in the case of the crude fiber. Although a gain 

 in crude-fiber digestion was indicated when the moisture content of the 

 feces was high, a loss was indicated under the third method, where there 

 is a direct measure of the rate of food passage. Crude-fiber digestion is 

 largely a biochemical digestion in which the time element is of impor- 

 tance, and it seems more tenable to assume that we have a less complete 

 digestion of crude fiber if the time of digestion is shortened by a more 



1 EwiNG, P. v.. Wells, C. A., and Smith, F. H. the assoclativg digestibility op corn silage 

 AND COTTONSEED MEAL IN STEER RATIONS. PART 2. Ga. Agr. Exp. Sta. Bul. 135. P- 149-164, illus. 



I9I7. 



