1917] ANIMAL PRODUCTION. 673 



method indicate that 70 per cent of the nitrogen of the feces from corn is of 

 metabolic origin, while those of the pepsin-pancreatin method and Jordan's 

 method indicated 84 per cent and 46 per cent, respectively. 



"All of the methods make the nitrogen of blood albumin appear more than 

 completely digestible, even the apparent digestibility being over 100 per cent; 

 thus, the feeding of blood albumin with corn seems to Increase the digestibility 

 of the corn protein to an extent more than sufficient to offset the incompleteness 

 of digestibility of the protein of this supplement." 



The apparent digestibility of skim milk varied from 95.97 to 104.44 per cent, 

 the average being 99.15. The proteins of skim milk appear to be more nearly 

 completely digestible by the acid-pepsin method than by the other methods. 



It is indicated that " important inaccuracy seems to be inevitable in any 

 determination of digestibility of supplementary foods in the usual way, by differ- 

 ence ; and no other method seems more satisfactory. This applies equally to 

 computations of real digestibility and of apparent digestibility (based on total 

 nitrogen of the feces). The digestion coefficients for protein involved in the 

 feeding standards of our reference works on animal production assume that the 

 nitrogen of the feces is entirely an indigestible food residue. The rough meas- 

 ures afforded by the results of this study indicate that, as applying to the 

 digestive capacities of swine, this assumption underestimates the digestibility 

 of protein by about 20 per cent." 



No significant differences were observed in the study of the effects on meta- 

 bolic nitrogen of storage of the feces in a frozen condition for 20 days, with or 

 without the addition of thymol, or air-drying the fresh material with or 

 without thymol. 



The acid-pepsin and the pepsin-pancreatin methods are considered to give 

 results which are more nearly true than does Jordan's method. The latter 

 does not digest the bacteria which may contain large proportions of the nitrogen 

 of the feces and which presumably are more largely the product of digestible 

 than of indigestible protein. The lack of an accurate scientific basis for the 

 determination of the digestibility of protein is noted. 



A study of the rate of passage of feed residues through the steer and its 

 influence on digestion coeffi^cients, P. V. Ewing and F. H. Smith {U. S. Dept. 

 Agr., Jour. Agr. Research, 10 (1911), No. 2, pp. 55-63). — In the investigations 

 here reported, which were made at the Georgia Experiment Station, the attempt 

 was made (1) to determine by means of digestion experiments the relationship 

 between the moisture content of the feces and the digestion coefficients in order 

 to see if there is a correlation between the time required for the passage of the 

 food through the animal and the moisture content of the feces, (2) to follow 

 more closely and directly by means of rubber markers the time required for 

 passage of the feed residues through the steers, and (3) to determine the rate 

 of passage by means of calculations based upon the intake of food and outgo 

 of feces and the alimentary tract contents as ascertained on slaughtering. 



In studying the problem by the first method essentially the digestion experi- 

 ments already noted (E. S. R., 34, p. 169) were repeated. To avoid the com- 

 plications in the calculations and results which would arise if comparisons were 

 made of the data obtained while on different rations, studies were made on the 

 correlations between the high and low moisture contents of the feces and the 

 corresponding digestion coefficients where the same rations were employed. 

 The correlations, as obtained from the results of the two series of digestion 

 experiments each made in duplicate, indicate that with a higher moisture content 

 of the feces there is a more complete digestion of all nutrients except nitrogen 

 and fat Commenting on the weakness of this method the authors state that " it 



