MEATS AS TROUT FOOD 



141 



sufficiently rich in vitamins. Fin<rerlin<r trout kept on beef or sheep 

 liver showed no evidence of vitaniin dehciency. With beef heai't, 

 however, the results were confusinj^. Finju:;erling i-ainbows made 

 a much better growth with less mortality when small amounts of 

 cod-liver oil and dry yeast were added to the meat. With brook 

 fingerlings, on the other hand, no appreciable difference could be 

 detected between the lots fed straight beef heart and those receiv- 

 ing small amounts of cod-liver oil and yeast in addition. Appar- 

 ently rainbow trout are more susceptible to vitamin deficiency than 

 are brook trout. In this connection it is interesting to note that 



2.55 



.80 



^ i 



M 



a 



I 



I 







60 



30 



I 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 7 18 19 20 21 22 23 24 25 26 27 28 



LOT NUMBER 



Figure 9. — Comparative growth and mortality of brook trout fingerlings on experi- 

 mental rations, July 12 to October 15, 1928. Since the fish in all lots were approxi- 

 mately the same size on July 12, comparisons are based on average individual 

 ■weights at the close of the experiment. Shaded columns indicate average individ- 

 ual weights in grams at the close of the experiment. Cross-hatched columns indi- 

 cate total mortality during the course of the experiment. The rations of the 

 individual lots were as follows: J = pig liver, 100. 2 = pig liver, 85; dry skim milk, 

 15. 3= pig liver, 50 ; beef heart, 50. .} = beef liver, 50 ; beef heart, 50. 5 = pig liver, 

 ■iSVs ; shrimp meal. 33% ; cod-liver meal, 33%. 6 = beef heart, 33% ; shrimp meal, 

 33%; cod-liver meal, 33%. 7 = beef liver, 33%; shrimp meal, 33%; menhaden 

 meal, 33%. S=- beef liver, 33%, ; shrimp meal, 33%; haddock meal, 33%. <)=beef 

 liver, 50 ; clam meal, 50. iO = beef liver, 33% ; clam meal, 33% ; shrimp meal, 33%. 

 Jl = beef liver, 50; mussel meal, 50. ^2=^pig liver, 50; mussel meal, 50. i3 = beef 

 heart, 85; dry skim milk, 15. /^ = beef heart, 50; cod-liver meal, 50. 7.5 = beef 

 liver, 50; shrimp meal, 50. 76= beef liver, 50: haddock meal, 50. i7 = pig liver, 

 50; haddock meal, 50. iS = beef liver, 50; menhaden meal, 50. i9=pig liver. 50; 

 menhaden meal, 50. 20 = pig liver, 50; shrimp meal. 50. 21 = beef liver, 50; "bone 

 loaf," 50. ;,'3 = "bone loaf," 100. 2.?=" bone loaf," 90; cod-liver meal, 10. 2i = 

 herring. 100. 25 = mackerel, 100. 2(;=shrimp, menhaden, mussel, and cod-liver 

 meals mixed in equal parts and fed 5 days a week ; beef liver 2 days a week. 27= 

 meals (as in 26), 80; dry skim milk, 20. 28 = meals (as in 26), 100 



Metzelaar (1929) has found that alga? form a considerable percentage 

 of the food of the wild rainbows, but this does not appear to be true 

 of the brook trout. 



These experiments on the addition of vitamin-rich products to 

 trout foods were fully described by Davis and James (1924), and 

 the reader is referred to this publication for further details. 



CONCLUSIONS 



As a result of our experiments we feel we are justified in reach- 

 ing more or less definite conclusions regarding the comparative 

 value of certain products as trout foods. We realize fully, how- 



