METHODS FOR STUDY OF DIGESTIBILITY OF LIPIDS 205 



Gallup and Kuhlman 20 stated that approximately 15% of silica was 

 metabolized; this would preclude its use for accurate experimental work. 

 Furthermore, Druce and Willcox 21 reported unsatisfactory results when 

 silica was used as an index in digestibility studies, since its recovery in 

 the feces was too variable. On the other hand, Skulmowski and co- 

 workers 22 found good agreement between the digestibility figure based 

 upon quantitative collection of the feces and one based upon the silica 

 ratio procedure. 



d. Chromic Oxide as an Inert Material in the Determination of Diges- 

 tibility. Chromic oxide (Cr 2 3 ) appears to be a compound which meets 

 all the prerequisites as an indicator substance. The use of this material for 

 determining digestibility was proposed as early as 1918 by Edin 23 ; the 

 method was later referred to as "Edin's indicator method." 



A number of workers have demonstrated the applicability of the chro- 

 mium oxide method under a variety of conditions, as well as with a 

 number of species. Its application for cattle was confirmed by Edin 

 and associates, 24 by Anderson alone 25 and with Frederiksen, 26 and by 

 Kane, Jacobson, and Moore. 19 Hamilton, Mitchell, and co-workers 27 

 were the first to employ chromic oxide in the United States. They showed 

 that it gave fairly satisfactory agreement in sheep as compared with the 

 conventional method (quantitative collection of feces), provided that the 

 collections were carried out for at least three days. The results on sheep 

 were confirmed by Barnicoat 28 and by Crampton and Lloyd; 29 Skul- 

 mowski et al. 22 reported similar findings for horses. However, Crampton 

 and Lloyd found that a period of five days must elapse from the start of 



20 W. D. Gallup and A. H. Kuhlman, J. Agr. Research, 52, 889-894 (1936). 



21 E. Druce and J. S. Willcox, Empire J. Exptl. Agr., 17, 188-192 (1949). 



22 J. Skulmowski, A. Szymafiski, and T. Wyszynski, Ber. Landw. Forschungsanstalt 

 General-Gouvernments, 1, 76-104 (1943); Chem. Zentr., 114, 1, 2460 (1943); Chem. Abst., 

 38, 4716 (1944); cited by E. A. Kane, W. C. Jacobson, and L. A. Moore, /. Nutrition, 

 41, 583-596 (1950), p. 584. 



23 H. Edin, Medd. Centralanslalt. forsoks-vdsendet jordbruks., No. 105 (1918); cited 

 by A. F. Schtirch, L. E. Lloyd, and E. W. Crampton, /. mdrition, 41, 629-636 (1950), 

 p. 630. 



24 H. Edin, G. Kihlin, and S. Nordfeldt, Lantbrukshogskol. Ann., 12, 166-171 (1944); 

 cited by E. A. Kane, W. C. Jacobson, and L. A. Moore, /. Nutrition, 41, 583-596 (1950), 

 p. 584; Chem. Abst., 39, 4358-4359 (1945). 



25 A. C. Anderson, Skand. Arch. Physiol, 69, 33-58 (1934). 



26 A. C. Anderson and L. Frederiksen, Biedermann's Zentr., Abt. A, 5, 334 (1935). 



27 T. S. Hamilton, H. H. Mitchell, C. H. Kick, and G. G. Carman, III. Agr. Expt. 

 Sta., 41st Ann. Report, Livestock Investigations, 119-121 (1927-1928); cited by A. F. 

 Schurch, L. E. Lloyd, and E. W. Crampton, J. Nutrition, 41, 629-636 (1950), p. 630. 



28 C. R. Barnicoat, New Zealand J. Sci. Technol, 27, Sect. A. 202-212 (1945). 



29 E. W. Crampton and L. E. Lloyd, J. Nutrition, 45, 319-327 (1951). 



