Effect of Method of Preparation on Utilization of Salmon Waste Meals 



That the biological value of proteins may be altered by ex- 

 cessive heat has been demonstrated, repeatedly, in feeding trials with 

 other animals. Because of the cooperative agreement with the Seattle 

 Technological Laboratory, it was possible to prepare meals derived 

 from exactly comparable sources, usint, standard techniques of pre- 

 paration, but employing different drying temperatures. In this man- 

 ner, all variables other than that of drying temperature were elim- 

 inated Two such series of experiments were included in the I9J48 

 feeding trials. I'he meals were prepared by tunnel and flame drying 

 as described by Karrick and Edwards (19U8). In the first series, using 

 Alaskan salmon offal as the source material, three different tem- 

 peratures were available, 100 degree and lli5 degree air-dried meals 

 and a commercial flame-dried meal derived from the same source. 

 The second group, using ^laskan salmon viscera, contained two tun- 

 nel-dried meals at 100 and ll;5 degree temperatures,, In both groups 

 the meals were added at the 10 per cent level to the standard meat 

 and viscera mixture. In the first series (Table 5 3 ^iets 12, 13, and 

 Ik) no significant difference existed bet-- en the groups of fish 

 fed the three diets. In the second evaluation (Table 5, ^iets 9 

 and 10), in which meals of higher growth potential were fed, a 

 significant difference in total c ;ains was demonstrated. The salmon 

 viscera meal dried at 100 degree temperatures was definitely su- 

 perior to the lii5 degree meal. The trend in the first series is 

 consistently in favor cf the lower drying temperatures at the con- 

 clusion of the 2U-week period. This trend is not apparent during 

 the first 12 weeks of the experiment. The gains which created the 

 differences between the diets occurred in the second 12-week period 

 indicating an acceleration in growth rate for that period in the 

 fish fed tunnel-dried meals which was superior to that of those 

 fed the flame-dried product. Had this experiment been conducted 

 only during the warm-water period, it is orobable that the addition 

 of low-temperature-dried meals would have produced gains which were 

 significantly greater than the flame-dried product. 



An acetone-extracted salmon viscera meal was tested in the 19k7 

 feeding trials. This meal was prepared from salmon viscera by a 

 process described by Karrick and Edwards (19^8) in which the tem- 

 perature during dehydration did not rise above 75 degrees F„ This 

 process is not in commercial use but if it could be demonstrated that 

 this method oroduced a superior meal, the development of a practical 

 procedure might be justified. The acetone-extracted meal was in- 

 corporated with the meat and viscera mixture at the 10 per cent 

 level and compared with a similar diet containing 10 per cent of \kS 

 degree, tunnel-dried, salmon viscera meal. The results of the 12- 

 week feeding trials indicated that no significant difference in growth 

 potential existed between the two meals. Vitamin analysis, as re- 

 ported by Karrick and Edwards (19li8) showed that the acetone-extraction 



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