FACTORS ALTERING NUTRITIONAL VALUE 919 



tion group, the calcium content of the rats twenty-one days old, and the 

 calcium balance of the growing animals maintained on this modified Sher- 

 man diet over a period of ninety daj^s, were more satisfactory than in the 

 case of animals recei\'ing the regular Sherman diet, which contains butter-fat 

 in place of a \'egetable margarine fat. WTien last reported (July, 1955) the 

 forty-second generation was being raised. There was no indication of nutri- 

 trional failure. Growth, fertility, and lactation were continuing at high 

 le^•els. The results of these experiments indicate that vegetable fat can 

 supply all the needs of the rat for fat o\er an indefinite period. 



(d) Other Nutritional Indices for Corn-paring the Nutritional Value of 

 Animal and of Vegetable Fats. Several other indices of nutritional value 

 ha^'e indicated that the comparative nutriti^-e ^'alues of butter and of 

 vegetable fats are essentially the same. Thus the so-called "survival fac- 

 tor," as suggested by Keane and Johnson^^^ occurs to the greatest extent in 

 wheat germ oil, although smaller amounts are present in butter. This is 

 the factor which is necessary to enable the female rat to rear her young to 

 weaning age successfulh'. Butter improves the survival rate considerabh'-, 

 but is less potent than wheat germ oil. This particular factor does not 

 appear to be identical with any of the known vitamins or essential fatty 

 acids. Lard does not contain this factor. The primary effect of the survival 

 factor is exerted in the in utero nutrition of the pup, but the factor is secreted 

 to some extent in the milk. It does not, however, appear to be necessary 

 for the lactation process. 



Stress as produced by cold environmental conditions is another nutri- 

 tional index which has been employed for comparing butter with vegetable 

 oils. Thus Ershoff, Pagones, and DeueP^" reported that the weight gains 

 of inunature female rats raised under cold room temperature conditions 

 on purified rations which differed only in the source of fat were significantly 

 less than the gains of rats maintained at normal room temperature. How- 

 ever, the gain in weight was approximately the same, irrespective of whether 

 butter, corn oil, cottonseed oil, or a vegetable margarine fat was emploj^ed 

 as a source of fat. 



Another condition which has been employed for the evaluation of butter- 

 fat and of vegetable oils has to do with differences in the carbohydrate 

 content of the foods. Thus, it was reported by Boutwell ei al.^'"^ that, when 

 rats were placed on a diet containing sucrose, a fructose-glucose mixture, 



»* K. W. Keane and B. C. Johnson, Federation Proc, 12, 418-419 (J953). 



^ B. H. Ershoff, J. N. Pagones, and H. J. Deuel, Jr., Proc. Soc. Exptl. Biol. Med., 70, 

 287-290(1949). 



»« R. K. Boutwell, R. P. Geyer, C. A. Elvehjem, and E. B. Hart, Arch. Biochem., 7, 

 143-157(1945). 



