In previous feeding trials in our lab with largemouth bass (LMB) fed soy-based diets, we observed significant rejection of the diets compared to a fish-meal control. Presumably, the soy diets were less palatable to LMB, reducing feed intake . Therefore, we designed a trial to combine different palatants with the same diet formulas to see if we could improve feed intake of the soy diets. Three basal diets were formulated to contain 40-42% protein and 10-12% lipid. The main protein sources in the basal diets were fish meal/poultry meal (control), traditional soybean meal (dehulled, solvent-extracted 48% protein) or PepSoyGen™, a fermented soy protein source . Diets were extruded as 2.5 mm floating pellets by Zeigler Bros., Inc., and shipped to UAPB where palatants were added at 2% of the diet using a cement mixer to top-coat pellets. The palatants included fish silage, chicken liver, and black rice vinegar . A total of 12 diets (3 basal diets alone or combined with 1 of 3 palatants) were produced for this 12-week feeding trial.
Twenty feed-trained juvenile LMB averaging 1.23 g initially were randomly assigned to 3 replicate 110-L tanks per diet in a recirculating system. F ish are being fed twice daily to apparent satiation and bulk-weighed by tank e very three weeks to monitor growth. M ortalities are recorded daily. Data is being analyzed using a 3x3 ANOVA. Nine-week average weight gain (g) data (below) showed that the fish meal diet performed better than either soy diet (P<0.05).
There are few significant effects of the palatants so far, but weight gain of fish fed the regular soy diet with chicken liver was not different from that of the fish meal control with no palatant. Feed intake was lower in fish fed the PepSoyGen™ diet with vinegar than the fish meal control diet (with or without vinegar). Survival of fish fed the regular Soy diet was higher than that of fish fed PepSoyGen™ , and survival of fish fed regular soy was similar to that of fish fed the fish meal diet. However, cannibalism is a complicating factor in assessing diet performance. Additional results will be presented at the meeting.