62 ^'. S. BUPiEAU OF FISHERIi:S 



and 2 per cent of dried yeast will produce fully as good results as do 

 lar<rer amounts. 



The beneficial results from the addition of oil and yeast to sheep 

 liver are not as evident as in the cast of heart, although a decreased 

 mortality and slightly increased growth were noted in some cases. 

 This was probably due to the fact that liver is much richer in vita- 

 mins than was formerly thought to be the case, and there are appar- 

 ently sufficient quantities of these substances present to promote 

 normal growth. 



In comparing the efficiency of heart and liver as a diet for young 

 trout it should be noted that at both Manchester and White Sulphur 

 Springs the best results were obtained with fish fed beef heart con- 

 taining small quantities of oil and j^east. Fish fed such a diet were 

 noticeably more active and vigorous than any of the other experi- 

 mental lots. However, the superiority of the heart, oil, and yeast 

 diet was more noticeable early in the season than later, and there is 

 some evidence that in practice it may be advantageous to change to 

 a liver diet after the fish are 3 to 4 months old. It is planned to 

 conduct further experiments along this line during the coming 

 summer. 



In conn ction with the work at White Sulphur Springs, feeding 

 experiments were carried on at the Wytheville (Va.) and Erwin 

 (Tenn.) stations. In each case rainbow-trout fingerlings were di- 

 vided into two lots of 2,000 fish each, which were kept under as 

 nearly identical conditions as possible. The only difference was in 

 the food, one lot (the controls) being fed a straight heart diet 

 while small quantities of oil and yeast were add d to the diet of 

 the other lot. Owing, no doubt, to the fact that both lots of fish 

 were fed the same amounts of food the dilference in growth w^as 

 not important, but a striking difference was noted in the mortality 

 of the two lots. 



At the Erwin station the experiment was complicated by the fact 

 that there was a very heavy mortality from pop. ye among all the 

 fingerlings, but even in this case the vitamin lot showed a distinct 

 superiority, the mortality being approximately .30 per cent less 

 than among the controls. It is also sig-nificant that in his report 

 th-' superintendent stated that the fish fed yeast and oil had a better 

 appearance and color than those given beef heart only. 



The experiment at the Wytheville station was more successful 

 and is still being continued. The total mortality between May 23 

 and Decemb r 23 was approximately 32 per cent in case of the 

 vitamin lot, while among the controls the mortality during the same 

 period was approximately 60 per cent. 



Experiments on tlie addition of cod-liver oil and yeast to the food 

 of brood trout to determine the effect on the quality of the eggs are 

 being carried on at the White Sulphur Springs, Wytheville, and 

 Erwin stations, but the results of thes^ experiments are not yet 

 available. 



At Madison, Wis., Dr. A. S. Pearse and three graduate students 

 have carried on investigations on the consumption and assimilation 

 of foods by fishes. For certain experiments painted turtles, terra- 

 pins, and gopher turtles were used because they are hardier than 

 fishes. The rat^ of growth of cold-blooded animals fed on mixtures 



