22 



16 percent starfish meal in the diets may be explained by bacterial synthesis of 

 riboflavin, and possibly other factors, during the early stages of the drying op- 

 eration in making the meal. The same effect had been noted by Lanham and Nilson 

 (1942) in a study of the possible toxicity of artificially spoiled pilchard meal. 

 In this case also, the diet containing the spoiled meal showed much better results 

 than the diet containing the commercial meal. Further work identified riboflavin 

 as one of the substances that stimulated growth which had been produced during the 

 spoilage of the meal. 



In the second series , the control group fed the pilchard meal showed very much 

 greater growth, although they received less than half as much pilchard meal, and 



2 percent less crude protein. This was the result of the adequate supply of ribo- 

 flavin. The relative nutritive values of the pilchard and starfish meal pro- 

 teins then may be evaluated with the proper prospective. 



The sharp decrease in gain in liveweight from 92 to 78.5 percent of that of 

 the control group, which occurred when the starfish meal in the mash was increased 

 from 6 to 9 percent, must be explained on some other basis than as a riboflavin 

 deficiency. The much-depended-upon explanation that the decrease is due to excess 

 calcium or an unbalanced calcium: phosphorus ratio does not appear valid. Five 

 percent of oyster shell was added to the control diet and lesser amounts to the 

 others so as to give all 4 diets a practically identical calcium content; The 

 range was only 2.71 to 2.86 percent calcium, making the range in calcium: phosphorus 

 ratios from 3.2:1 to 3.4:1. The control group and the groups fed diets containing 



3 and 6 percent starfish meal made very good growth, with a mean gain in liveweight 

 of 833, 765, and 770 grams, respectively, at the end of 8 weeks. 



The extraordinary tolerance of chicks for large amounts of calcium is also 

 evidenced by the surviving chickens fed the high levels of starfish meal in Series 1. 

 With mashes containing 32 percent starfish meal, the diet contained almost 18 

 percent calcium carbonate with no compensating source of phosphorus (calcium: 

 phosphorus ratio of 11 to 1) . Yet these chicks lived and more than doubled their 

 weight in 5 weeks after the thiamine supplementation was started. 



There are two other possible explanations for the sharply decreased rate of 

 growth when increased amounts of starfish meal were included in the feed: either 

 the poor quality of the protein or the presence of some other substance carried 

 by the starfish that is detrimental, above certain levels. 



All evidence indicates that the starfish protein is very nearly equal to any 

 other marine protein supplement in biological value, when the amount used does 

 not exceed 6 percent. It is suggested that the major factor in the interference 

 with growth of chicks fed levels of starfish meal ranging from 6 to 18 percent, 

 is the presence of thiaminase, the thiamine-destructive enzyme, in starfish meal 

 which has been dried at a low temperature. 



The hypothesis is advanced that the thiaminase content of the diet explains 

 the results of the present test, as well as the similar results noted by Heuser 

 and McGinnis (1946) who fed 6 and 12 percent levels of starfish meal, by Ringrose 

 (1946) who fed 9 and 18 percent levels, and by Whitson and Titus (1946) who fed 

 a 12 percent level of starfish meal. It is notable that a sun-dried meal was 

 used by all these investigators. The one series in which a meal was fed that 

 had been dried in commercial drying equipment (Morse, et al, 1944) resulted in 

 better growth with the 8 percent than with the 4 percent level of starfish meal. 

 This result was obtained with a meal containing only 27.5 percent crude protein 



