| The inclusion of bioprocessed soybean (Glycine max ) meal was evaluated in five experiments using either Rainbow Trout (Oncorhynchus mykiss) or Brown Trout (Salmo trutta ). In the first experiment, adult Erwin x Arlee strain Rainbow Trout were fed diets formulated so that bioprocessed soybean meal (BSM) replaced 0, 60, or 80% of the dietary fishmeal. There were no significant differences in gain, percent gain, feed conversion ratio, specific growth rate, intestinal morphology, relative fin lengths, or organosomatic indices. In the second experiment, juvenile Plymouth strain Brown Trout were fed diets formulated so that BSM replaced 0, 60, 80, or 100% of the dietary fishmeal. Similar to the first experiment, there were no significant differences in gain, percent gain, specific growth rate, percent mortality, intestinal morphology, relative fin lengths, or organosomatic indices among the diets. Differing water velocities were an additional factor included in the final three experiments. The third experiment fed adult Erwin x Arlee strain Rainbow Trout diets where BSM replaced either 0 or 60% of the dietary fishmeal. Two velocity treatments of 3.6 or 33.2 cm/s were also included in the 2x2 study design. Neither diet nor velocity had any significant impact on gain, percent gain, specific growth rate, intestinal morphology, relative fin lengths, or organosomatic indices. However, feed conversion ratio was significantly lower in the lower velocity treatment compared to the higher velocity treatment. The 60% BSM diet also had a significantly lower feed conversion ratio than the fishmeal reference. There were also no interactions between diet and velocity. The fourth experiment examined juvenile Shasta strain Rainbow Trout fed three different where BSM replaced 0, 60, or 80% of the dietary fishmeal in conjunction with two different velocity treatments of 2.3 or 18.7 cm/s. The fish being fed the fishmeal diet ate significantly greater amounts of food than the 80% bioprocessed soybean meal diet. However, there were no significant differences among the diets in gain, percent gain, specific growth rate, percent mortality, relative fin length, intestinal histology, viscerosomatic index, or splenosomatic index among the diets. The fish at the lower velocity had significantly decreased growth compared to the fish at higher velocity. There was also a significant interaction between diet and exercise for the amount of food consumed. The fifth, and final, experiment examined juvenile Plymouth strain Brown Trout being fed diets where BSM replaced either 0 or 60% of the fishmeal and subjected to velocities of 2.8 or 16.1 cm/s. There were no significant differences in gain, percent gain, feed conversion ratio, specific growth rate, intestinal morphology, splenosomatic index, hepatosomatic index, or viscerosomatic index for the fish receiving either diet. However, gain, food fed, and specific growth rate were significantly higher for fish at the higher velocities. There were no significant interactions between diets and velocity in this experiment. In experiment three and experiment five towards the end of the experiments there was a significant decline in gain, percent gain, and specific growth rate for the fish reared in higher velocities, perhaps indicating exercise fatigue. Based on the results of these experiments, BSM can replace 100% of the fishmeal meal in diets of Brown Trout during normal rearing, and at least 60% of the fishmeal during continual exercise. Bioprocessed soybean meal can replace at least 80% of Rainbow Trout diets, regardless of the exercise regimen. |
