The results of this experiment indicated that the hog 

 liver - arrow -toothed halibut - salmon -viscera mixture 

 was equal to the standard meat-viscera diet in growth 

 potential and could be recommended for production use. 

 The meat-fish -viscera diet was more economical since 

 it contained only 25 percent liver whereas two -thirds 

 of the meat-viscera mixture was composed of relative- 

 ly high cost meats . Hog liver proved superior to either 

 beef lung or hog liver and beef lung together when these 

 meats were fed in combination with arrow-toothed 

 halibut and salmon viscera. Hake produced less 

 growth response than arrow-toothed halibut in compar- 

 able mixed diets . 



RESULTS CF THE 1954 EXPERIMENTS 



In 1954 the blueback feeding trials were designed 

 to test the growth potential of heat treated salmon 

 viscera and to develop adequate hatchery diets that 

 contained no salmon viscera. The Chinook experiment 

 was designed to test the effect of higji-meal diets, 50 

 percent level, in the rations of chinook salmon . 



Blueback Salmon 



Since raw salmon viscera was suspected to be the 

 carrier of the virus disease, two methods of approach 

 to the problem of developing virus-free diets were ex- 

 plored . The first involved sterilization of the salmon 

 viscera with heat and the second the development of 

 efficient diets devoid of salmon viscera. Both methods 

 were tried in the 1954 experiment . At the end of the 

 first 12 -week period all diets except Mets 4 and 12 

 were altered to include 10 percent of salmon offal meal . 

 The results of the blueback trials are summarized in 

 Table 2 . 



Two factors may be responsible for the lowered 

 growth potential of the heat-treated salmon viscera. 

 The most obvious was the poorer feeding consistency 

 of these products . The heat treatment apparently 

 destroyed the binding quality of the salmon milt and 

 therefore allowed the feed to leach. The canned vis- 

 cera was more nearly comparable to the raw viscera 

 in this respect than was the pasteurized product. Al- 

 teration of the biological value of the protein and/or 

 destruction of essential vitamins due to heat treatment 

 may also have been factors responsible for the poorer 

 growth of the sterilized viscera diets . Regardless of 

 the cause, the heat treatment resulted in an inferior 

 product. 



A diet consisting of 100 percent beef liver (Diet 4) 

 was included merely as a comparison with the work of 

 other investigators who use this product as a standard. 

 The growth of fish fed this diet was exceeded signifi- 

 cantly by all diets in the experiment except Diets 2 

 and 12 . 



Salmon viscera was eliminated from the remaining 

 diets in the experiment (Diets 5 through 12). These 

 diets utilized instead other fish products and meat or 

 meat and meal combinations . Squawfish (Ptychocheilus 

 oregonensis ) and arrow -toothed halibut were compared 

 in Diets 5 through 8. Squawfish are fairly abundant in 

 the lower Columbia River and are known to prey on 

 young salmon. Sufficient demand for squawfish for 

 hatchery diets might stimulate commercial fishing for 

 this species and thereby relieve the predator situation 

 as well as provide a source of fish food. Arrow-toothed 

 halibut is being used in hatchery production diets. 

 Sufficient quantity is available to meet the demands of 

 Pacific slope hatcheries . 



Two types of heat treatment were used in this ex- 

 periment . The frozen salmon viscera was thawed and 

 canned in No . 1 tall tins . One lot was pasteurized for 

 15 minutes at 50° C, the other lot cooked for 90 

 minutes at 100° C. It was necessary to keep the pas- 

 teurized lot in frozen storage while the cooked viscera 

 was stored at room temperatures. The diets contain- 

 ing the heat-treated viscera were prepared and fed in 

 the usual manner. 



A basic mixture of 25 percent hog Uver and 25 per- 

 cent arrow -toothed halibut was fed with 50 percent 

 raw viscera (Diet 1), with 50 percent pasteurized vis- 

 cera (Diet 2), and with 50 percent cooked viscera 

 (Diet 3) . 



The growth response from the raw viscera and 

 the cooked product was quite similar for the first 12 

 weeks of the experiment. The pasteurized viscera 

 produced significantly less growth than the other two 

 viscera diets . Results at the end of the 24-week period, 

 however, showed the raw viscera definitely superior 

 to the two heat-treated products. The final weight of 

 the cooked viscera diet (Diet 3) was significantly less 

 than that of the diet containing raw viscera (Diet 1). 

 Even less growth resulted from the pasteurized vis- 

 cera (Diet 2) . 



Squawfish and arrow -toothed halibut were compared 

 at the 25 -percent level in combination diets containing 

 beef liver, hog Uver, and beef lung (Diets 5 and 6) and 

 at the 50 -percent level in diets containing hog liver and 

 beef lung (Diets 7 and 8). At the 25 -percent level squaw- 

 fish compared favorably with arrow-toothed halibut. No 

 significant differences in final weights of the two diets 

 occurred. Mortalities and conversions were similar 

 for both. The halibut diet (Diet 8) proved superior in 

 growth production to squawfish (Diet 7) when these 

 products were fed at the 50 percent level . At the end 

 of 24 weeks the final weight of the Diet 8 fish was sig- 

 nificantly higher than those of Diet 7 . The amount of 

 hemoglobin was low in the fish fed the halibut diet 

 (Diet 8). Apparently this diet was deficient in the 

 antianemic factor. No such deficiency was present in 

 the squawfish diet (Diet 7). 



Dry meal supplements were included in Diets 9 

 through 12. The hog liver - beef lung - arrow-toothed 

 halibut mixture (Diet 8) was used as the base for three 

 diets (Diets 9, 10, and 11), and proportional reductions 

 in these components were made when dry meals were 

 added. The last diet (Diet 12) contained only hog liver 

 and beef lung with 50 percent of dry meal . This meal 

 mix consisted of the 50 percent distillers solubles and 

 25 percent each of wheat middlings and cottonseed meal. 



