MODIFIED SOYBEAN MEALS AS SUSTAINABLE PROTEIN SOURCES IN DIETS OF LARGEMOUTH BASS (Micropterus salmoides)

A 12-week feeding trial was conducted with juvenile Largemouth Bass (Micropterus salmoides) with an initial average weight of 12.1g to determine the performance of fish fed diets with different soybean meals or fish meal.  Six diets were formulated.  One diet contained menhaden fish meal, while the others contained soybean meals modified in different ways to improve their nutrient composition.  The soybean meals included a standard soybean meal (dehulled, solvent-extracted 48"% protein), an acid hydrolyzed meal, a hot-water treated meal, and two fermented soybean meals (Fermented Soy 2 and Pepsoygen™).  The objective was to determine if there would be differences in growth, survival, feed conversion ratio (FCR), hematological parameters, non-specific immunity, hepatosomatic index, and whole body composition.  The fish were fed twice daily to satiation.  Data was analyzed using 1-way ANOVA and considered significant at p≤0.05.

The fish fed the fish meal diet had higher weight gain than the fish fed the Pepsoygen™ diet, but the Pepsoygen™ diet was higher than the other soy diets.  The FCR was lowest (best) in the fish fed the fish meal or Pepsoygen™ diets and highest in the Fermented Soy 2 diet.  The FCR of the fish fed the fish meal or Pepsoygen™ diets did not differ.  The alternative complement activity and hepatosomatic index were higher in fish fed the Pepsoygen™ diet.  Total lipid concentration of the whole body samples was highest in fish fed the fish meal diet. Survival, hematological parameters and lysozyme activity did not differ among diets.  The fish meal diet and the Pepsoygen™ diet worked well in two key areas.  While growth was higher in the fish fed the fish meal diet, Pepsoygen™ appears to be a promising alternative protein source.