meal mixture should not be included in the diet of blueback salmon 

 during periods of low water temperature. 



Of the numerous diets tested in the Leavenworth feeding trials 

 only the beef liver-hog liver starting diet, the meat and viscera, 

 and meat-viscera-meal rations have been evaluated sufficiently as 

 production diets to recommend their adoption in actual production 

 operations. These diets have proved practicable and are apparently 

 nutritionally adequate as rations for blueback salmon. 



The Effect of Cold Storage on Prepared Diets. 



The problem of diet preparation is very real and pertinent, 

 particularly to fish-cultural operations conducted on a small 

 scale. Most of the diet preparation equipment available on the market 

 is expensive and not adapted to the preparation of small quantities 

 of food. For these reasons, such equipment is not applicable to 

 small-scale operations. If diets could be prepared in a central 

 plant, packaged, stored under refrigeration, and delivered to the 

 stations as required, much of the cost of diet preparation which is 

 contained in duplicate equipment and the inefficiency of limited 

 operations could be eliminated. 



Feeding trials were conducted during 1°U5, 19il7, and 19^8 to 

 test prepared diets which had been held in frozen storage for a 

 period of 60 days or more before being fed. In these experiments, 

 the diet components, with the exception of salt, were ground and 

 mixed while in a frozen condition and packed in small, commercial, 

 cardboard, freezing cartons while still in a frozen state. The 

 prepared diets were held at a refrigerative temperature of -10 degrees 

 The size of the cartons varied from one-half pints to quarts. A 

 sufficient number of cartons to meet the daily requirement of the 

 fish were withdrawn from storage, allowed to soften slightly, broken 

 into small pieces, and bound by mixing and the addition of salt when 

 a binder was present in the diet. 



In the 19U5 experiments, three frozen prepared diets were 

 tested. In all diets the meat and meal composition was the same 

 and the variables, salmon viscera, salmon carcass, and tuna viscera, 

 were introduced at the 30 per cent level (Table 3» Diets lli, 15, and 

 16). The diets containing tuna viscera and salmon carcass had to be 

 discontinued before the conclusion of the lli-week experimental period 

 due to an acute anemia in both groups of fish. The diet containing 

 salmon viscera, on the other hand, showed no evidence of an anemia 

 and exhibited a growth potential comparable to its freshly-prepared 

 counterpart (Table 3, Diet 9). That both tuna viscera and salmon 

 carcass produced an anemia is not surprising in view of the other 

 experimental results. Phillips and Hewitt (19^5) concluded that 



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