NORMAL FACTORS ALTERING DIGESTIBILITY OF FATS 229 



on a number of other species. According to Schneider, 93 soybean seed, 

 with a fat content of from 15 to 17%, has the following coefficients of 

 digestibility: cattle, 98; sheep and goats, 84-95; and pigs, 84. Palm 

 kernel oil, present to the extent of 20% in the meal, was digested by sheep 

 and goats to the same extent as was soybean oil. Cottonseed oil, found 

 in the cottonseed cake to the extent of 7%, was shown 86 to have a co- 

 efficient of digestibility of 96. Soybean and peanut oils are reported to 

 be well utilized by the pig. 94 Guntherberg 95 found that ordinary fats 

 are well absorbed by the hen. Even the trout, which has a very low 

 body temperature, has been shown by McCay 96 to utilize relatively high- 

 melting fats to the extent of 57%, without any apparent injury. 



U) The Effect of Melting Point 



In general, an inverse relation exists between melting point and di- 

 gestibility for fats melting at temperatures above 50°C. 2,97 Cheng and 

 her associates 5 reported that this inverse relationship exists in the ab- 

 sorption of simple triglycerides in the rat. Figure 1 shows the relation- 

 ship between the percent of unabsorbed fat and the melting point of the 

 fat. 



In analyzing the relationship of melting point of a fat to its digestibility 

 in rats, Deuel 98 has shown that the greatest increase in fat excretion occurs 

 in the soap fraction. A summary of these results is given in Table 15. 



Paul and McCay 73 state that the melting point of a fat is important in 

 determining its utilization by guinea pigs, but that this is not the case 

 with rabbits and sheep. 



On the other hand, Hoagland and Snider 99 have pointed out that their 

 experiments do not support the thesis that a definite relationship exists 

 between melting point of a fat and digestibility. Thus, they found that 

 mutton tallow (m.p., 47°C.) had a higher coefficient of digestibility than 



93 B. H. Schneider, Feeds of the World, West Va. Agr. Expt. Sta., Morgantowu, 

 West Va. (1947); cited by R. P. Cook, "Comparative Aspects of Lipid Absorption and 

 Excretion," in R. T. Williams, Lipid Metabolism, Biochem. Soc. Symposia, No. 9, Cam- 

 bridge Univ. Press, 14-26 (1952), p. 16. 



•* N. R. Ellis and H. S. Isbell, J. Biol. Chem., 69, 219-238 (1926). 



98 K. Guntherberg, Wiss. Arch. Landwirtsch., Abt. B, Arch. Tierernahr. u. Tierzucht, 

 S, 339-367 (1930); Chem. Abst., 25, 5451 (1931). 



96 C. M. McCay, Ann. Rev. Biochem., 6, 445-468 (1937). 



97 A. D. Holmes and H. J. Deuel, Jr., Am. J. Physiol, 54, 479-488 (1921). 



98 H. J. Deuel, Jr., "Nutritional Value of Soybeans and Soybean Products," in K. S. 

 Markley, ed., Soybeans and Soybean Products, Vol. II, Interscience, New York-London, 

 1951. 



99 R. Hoagland and G. G. Snider, J. Nutrition, 25, 295-302 (1943). 



