324 CARNEGIE INSTITUTION OP WASHINGTON. 



NUTRITION. 



Osborne, T. B., and L. B. Mendel, New Haven, Connecticut. Continuation 

 and extension of work on vegetable proteins. (For previous reports see 

 Year Books Nos. 3-15.) 



In our report for 1916 we stated that our results with commercial 

 by-products, which are extensively used to increase the protein in 

 rations fed to domestic animals, fully justified a continuance of these 

 investigations and their extension to other largely used commercial 

 products. Accordingly we have made a more detailed study of the 

 effect of diets containing each of a larger number of such products as 

 well as of combinations of these in various proportions. These inves- 

 tigations have shown wide differences in nutritive value between manj'' 

 of the substances tested, especially in respect to the rate of growth in- 

 duced by equal quantities of them. Thus, young albino rats on a diet 

 containing 9 per cent of protein in the form of cotton-seed flour in a 

 given time gained as much in weight as those on a diet containing 18 

 per cent protein in the form of brewers' grains, the total food intake 

 being the same, whereas when 9 per cent of protein in these latter grains 

 was fed no growth at all was made. 



Combinations of two such feeds were frequently more efficient than 

 even larger proportions of either one alone. Thus, on a diet containing 

 6 per cent of soy-bean protein and 10 per cent of corn-gluten protein a 

 gain of 51 grams was made in 3 weeks, whereas on a diet containing 

 15 per cent of corn-gluten protein alone 12 weeks were required to 

 make the same amount of growth. Various proportions of many pro- 

 tein concentrates in numerous combinations were thus tested, with 

 results which may guide those engaged in developing more econom- 

 ical methods of feeding domestic animals than are now in use. 



The experiments with cotton-seed products mentioned in our last 

 report have been extended and the results there described have been 

 confirmed. It has been shown that the decorticated seeds contain 

 something which is either toxic or so unpalatable that rats refuse to 

 eat enough of the foods containing even small quantities of meal made 

 from them to support life. This "toxic" substance is not present in the 

 oil, for cold-pressed cotton-seed oil added to the diet in liberal amounts 

 fails to affect the animals unfavorably. The ether extract from the 

 cold-pressed seed residues contains the deleterious substance, for even 

 a little of the sohd from such extracts seriously impairs the value of 

 the food. The ether-extracted meal promotes normal growth. 



We found, with rats, that all the difficulties encountered in feeding 

 cotton-seed meal, which have generally been attributed to a toxic 

 substance in this seed, can be eliminated by heating the ground seed with 

 steam. As this is usually done in the oil-mills before pressing out 

 the oil, it is probable that the commercial meal can be rendered harm- 



