METHODS FOR STUDY OF DIGESTIBILITY OF LIPIDS 207 



mogenic material which has been suggested as an indicator by Corbin 

 and Forbes. 38 When this material was fed to lambs, it could be quanti- 

 tatively recovered from the feces, and so should serve as an indirect 

 means for estimating digestibility. However, this substance was shown 

 to be subject to the same limitation as chromic oxide. It was found 

 that the dye was not excreted uniformly; morning and evening samples 

 of feces contained less dye than did samples excreted at noon. 



f. Comparison of Different Technics for the Determination of Digesti- 

 bility. On the basis of a comprehensive study of the digestibility of dry 

 matter, crude protein, crude fiber, nitrogen-free extract and ether extract 

 of alfalfa silage, field-cured and barn-cured alfalfa, Kane and co-workers 19 

 showed that both the chromic oxide and the lignin methods are satis- 

 factory insofar as the cow is concerned. The comparative values for 

 digestibility of the several fractions of the diet as calculated by total 

 collection, chromic oxide method, and lignin method are summarized 

 in Table 5. 



Table 5 



Summary Table Showing the Coefficient of Digestibility of Various 



Dietary Fractions in Cows, as Determined by the Total Collection of 



Feces or by the Use of Chromic Oxide or Lignin as an Indicator" 



Dry Crude Crude N-free Ether 



Indicators matter protein fiber extract extract 



Alfalfa silage 6 



Total collection 61.2 63.8 43.2 72.4 66.1 



Cr 2 3 method 61.4 64.0 43.4 72.4 66.2 



Lignin method 61.8 64.2 43.8 72.7 66.6 



Field-cured alfalfa 6 



Total collection 59.5 61.8 44.9 70.7 55.9 



Cr 2 3 method 59.1 61.4 44.4 70.5 55.4 



Lignin method 58.7 61.0 43.8 70.2 55.0 



Barn-cured alfalfa 6 



Total collection 63.6 68.6 46.7 74.0 52.7 



Cr 2 3 method 63.8 68.8 46.9 74.1 52.9 



Lignin method 62.4 67.6 45.0 73.2 51.2 



° Data adapted from E. A. Kane, W. C. Jacobson, and L. A. Moore, /. Nutrition, 41, 

 583-596(1950). 



6 Three cows, six tests per group. 



(6) Determination of Fecal Lipids 



a. Methods Employing Dried Feces. In the extensive program on fat 

 digestibility carried out by the U.S.D.A. on human subjects, and in most 



38 J. E. Corbin and R. M. Forbes, ./. Animal Set., 10, 574-580 (1951) 



