32 



THIAMINASE IN STARFISH MEAL 



It has already been noted that thiaminase remaining in starfish meal was a 

 factor adversely affecting the growth of chicks fed a mash formula used to determine 

 the value of the meal as a protein supplement . 

 These chicks had been fed on high levels of 

 starfish meal; namely, 32 percent regular meal 

 and 29.5 percent extracted meal. These levels 

 were fed primarily to determine the tolerance 

 of the chick for excess calcium, and an un- 

 balanced calcium: phosphorus ratio. Thiamine 

 in the mash was supplied by bran, middlings, 

 and other grain products , and was adequate in 

 the diets containing pilchard meal and the low- 

 er levels of starfish meal . 



There were no deaths in these groups until 

 the 13th day of test, but 11 of 21 chicks died 

 during the next 8 days . It was thought possible 

 that this heavy mortality after 2 weeks might 

 be due to a thiamine deficiency resulting from 

 the presence of thiaminase which had not been 

 destroyed by the low drying temperatures. After \ 

 3 weeks, therefore, 100 micrograms of thiamine I 

 per 100 grams of mash was added to both diets , 

 containing the high levels of starfish. The i 

 surviving chicks showed much improvement in ) 

 condition and fairly good growth response dur- 

 ing 5 weeks they were fed on the diets supple- 

 mented with thiamine as shown in Figure k. 



The slightly better growth of the group 

 fed the extracted meal was probably due to the 

 extraction or destruction of some thiaminase 

 during the prolonged extraction with hot ace- 

 tone. The thiamine supplement was therefore 

 doubled for the group fed the regular meal 

 after 2 weeks on the 100-microgram level, .and 

 a. further response in growth was obtained (see 

 Figure 4). 



A - THIAMINE DEPLETION DIET 



B - PLUS I0)< RAW STARFISH 



C - B PLUS 10 MICROGMS. THIAMINE 



- 6 „ " „ 



12 3. 



WEEKS 



FIGURE 3 - GROWTH CURVES FOR RATS RE- 

 CEIVING THIAMINE BASAL TEST OIET 

 ALONE AND ADMIXED WITH 10 PERCENT 

 STARFISH, BOTH WITH AND WITHOUT SUP- 

 PLEMENTS OF 10. 25, AND 60 MICROGRAMS 

 THIAMINE PER 100 GRAMS DIET. .ALSO 

 THE GROWTH CURVE OF THE GROUP FED THE 

 BASAL TEST DIET WITHOUT STARFISH BUT 

 PLUS 25 MICROGRAMS OF THIAMINE PER 

 1 00 GRAMS. 



Growth, even when the diet was supplemented 

 with 200 micrograms of thiamine per 100 grams 

 of mash, did not approach normal for the age 

 of the chicks . There is no proof that even 

 this relatively large amount of thiamine sup- 

 plied an optimum level. Feeding tests of the same type conducted by other in- 

 vestigators have shown that the addition , for example , of 200 micrograms of thiamine 

 to a mixture containing thiaminase may result in the loss of 90 percent, which is 

 equal to 180 micrograms of thiamine. If much larger amounts, perhaps 1,000 micro- 

 grams , were added , larger actual quantities , but a smaller proportion of the total , 

 for example, 700 micrograms, may be destroyed by the same amount of thiaminase. 



On the other hand, the excess calcium carbonate, amounting to almost 18 per- 

 cent of the diet, was undoubtedly also a factor tending to retard growth but the 



