DIGESTIBILITY OF SOME ANIMAL FATS. 



21 



severe muscular activity, but should meet the needs of those follow- 

 ing sedentary occupations. 



It is interesting to know whether or not the presence in the diet of 

 the different fats in considerable quantity affects the digestibility of 

 the other constituents and the coefficient of availability of the ration 

 as a whole. It has been shown by work previously reported 1 that the 

 total available energy and the ' ' coefficient of availability of energy " can 

 be calculated with reasonable accuracy. The average coefficients of 

 availability of energy for the rations as calculated were 93.0 per 

 cent, 92.7 per cent, 91.5 per cent, and 93.9 per cent for the diets 

 containing lard, beef fat, mutton fat, and butter, respectively. 

 These values agree with one another closely and are somewhat higher 

 than the value 91 per cent which has been found to represent the 

 coefficient of availability of energy of the ordinary mixed diet. 2 It 

 is reasonable to conclude, therefore, that the different fats did not 

 exercise any unusual effect upon the digestibility of the other con- 

 stituents of the rations. 



The statement has frequently been made that the coefficients of 

 digestibility of fats are directly related to the corresponding melting 

 points. The melting points of samples of the fats studied or of samples 

 of fats similarly prepared are reported in the table below together 

 with a compilation of values 3 determined by several investigators 

 giving, presumably, the average range found in samples fairly 

 true to name. The variation in the melting points of different 

 samples of the same fat is consistent with the view that the melting 

 points differ with the part of the body in which the fat is found and 

 also with the animal from which it is taken. 



Comparison of digestibility and melting point. 





Coefficient of digesti- 

 bility. 



Melting point. 



Fat studied. 



Deter- 

 mined. 



With allow- 

 ance for 

 metabolic 

 products. 



Authors' 

 determina- 

 tions. 



Compiled 

 average 

 values. 1 



Butter fat 



Per cent. 

 94 

 94 

 89 

 80 



Per cent. 

 97 

 97 

 93 

 88 



Degrees C. 

 32.0 

 35.0 

 45.0 

 50.0 



Degrees C. 

 28-36 

 30-44 

 42-50 

 47-49 



Lard 



Beef fat 



Mutton fat 





1 Allen's Commercial Organic Analysis. Philadelphia: Blakiston's Pon & Co., 1910, 4. ed., vol. 2, p. 72. 



It seems fair to conclude that of those tested the fats of low melting 

 points are capable of more complete assimilation than those which 

 have a high melting point. 



1 Connecticut Storrs Kta. Itpt. 1M), p. 104. 



*U?S. Dept. Agr., Expt. Kta. Bui. 130 (1903), p. 113. 



• A lien's Commercial Organic Analysis. Philadelphia: Blakiston's Hon & Co., 1910, 4. ed., vol. 2, p. 72. 



