140 



U. S. BUREAU OF FISHERIES 



At the request of Swift & Co., we tested one of their canned-meat 

 products which is on the market under the trade name of " Silver 

 Fur Food." This is a bahinced ration put up expressly for the 

 feeding of foxes on fur farms. 



Brook-trout yearlings on this diet made a satisfactory errowth 

 during the course of the experiment (fig. 11) with no marked mor- 

 tality appearing, as is often the case when using a straight diet 

 of dry or cooked foods. The period of feeding, however, was not 

 sufficiently long to justify any final conclusions as to its real worth. 



X MORTALITY 



5 10 15 20 25 30 35 40 



^ 3.5 



e? 



2.5 



> 



1.5 



uJ 



Figure S. — Compurntive growtli and mortality of rainbow fingerlings fprt 

 beef liver, soybean meal, and Mexican jtinto beans. lil=hvvl liver, 100 

 (control). ii-'/ = beef liver, 75; Mexican pinto beans, 25. /{~ = beef liver, 

 75 ; soybean meal, -5 



Should this or a similar product prove a satisfactory substitute 

 for part of the fresh-meat rations of trout it would doubtless be 

 found welcome in many situations. The advantage of having on 

 hand a constant supply of food, the feeding of which involved only 

 the minor difficulties of opening tins, would alone make it pox)ular. 



COD-LIVKH OIL AND YEAST 



Many of tlie earlier experiments were designed primarily to deter- 

 mine if the foods ordinarily supplied to trout at hatcheries are 



