62 Journal of Agricultural Research voi. x, no. 2 



It was only by means of the slaughter test that we were enabled to 

 arrive at an accurate measure of the specific time required for the passage 

 of a certain ration residue through the steer. As already stated, the resi- 

 due from any given feeding may require for its complete expulsion several 

 weeks, or even months. The figures obtained express the average time 

 required for passage, the calculation being based upon the dry matter 

 of the feeds, the content of the digestive organs, and the resultant feces. 

 Expressed as a formula: 



C 

 ^. Amount „ "dTT' 

 Time = — fs-T — , or T=R+F 

 Rate 



2 



in which T represents time units required for passage of food residue, 

 C the dry-matter contents of the alimentary tract of the steer as deter- 

 mined at the time of slaughter, R the dry-matter content of the ration 

 per given unit of time, and F the dry-matter content 01 the feces voided 

 for the given unit of time. 



In making use of this formula it is recognized that certain end products 

 of digestion, such as residues from digestive juices, cell destruction, and 

 bacterial life, may interfere with the accuracy of the method; but the 

 interference can be no greater than in the case of the determination of 

 digestion coefficients, which are influenced by the same factors when the 

 usual method of determination is employed. 



Among other things the greater length of time required for the passage 

 of food residues in the case of the coarser feed was noticeable. Like- 

 wise, where the ration or feed is the same, a greater time will be required 

 for the passage of residue from the smaller quantity. In the cases of the 

 two compounded rations, which might be classed as normal rations, 

 the rate of passage of feed residues did not vary a great deal and were 

 between 72 and 84 hours, which might be taken as the average time re- 

 quired for the passage of feed residues through steers on normal rations. 

 The third method of study shows that it is quite probable that, associated 

 with a more rapid passage of feed residue, we have a more complete 

 digestion of all nutrients except crude fiber. Therefore, in actual 

 feeding practice it is desirable that a rapid passage of feed residues be 

 encouraged, since any loss in crude-fiber digestion may be a net gain in 

 energy units on account of the high cost in energy for the digestion of 

 this nutrient. 



CONCLUSIONS 



(i) In general, a more complete digestion is associated with a more 

 rapid passage of feed residue through the steer. 



(2) Crude-fiber digestion seems to be decreased with a more rapid 

 passage of feed residues. 



(3) Coarse feeds and roughages retard the rate of passage of residues. 



