The objective of this study was to evaluate the effect of plant-based diets containing different inclusion levels of a fermented soybean meal (FSBM) prepared with a mixed microbial culture on the intestinal morphometry of Nile tilapia (Oreochromis niloticus) juveniles reared in a BFT system. FSBM was evaluated at four inclusion levels (7%, 14%, 21% and 28%) and compared to a positive control diet with fish meal and a negative control diet with no animal protein nor FSBM.
Soybean meal was fermented with a mixed microbial culture containing Lactobacillus acidophilus, Saccharomyces cerevisiae and Enterococcus faecium. All diets were isoprotein (33% CP) and isoenergetic (4300 kcal GE/kg). The design was completely randomized with four replications. Nile tilapia juveniles (1.635±0.198 g) were distributed in 24 tanks (70 L) at a density of seven animals per experimental unit. The tanks were connected to a recirculation system equipped with heating and aeration. Water quality parameters were periodically monitored. After 54 days of the experiment the intestinal morphometry was evaluated.
The soybean meal fermentation increased lactic acid bacteria and yeast counts (Table I). A reduction in pH was observed in the FSBM and there was also an increase in soluble protein. In animals fed 21% and 28% FSBM diets, higher (P<0.0,5) villi height were observed compared to the other treatments (Figure I). In the inclusion of 28% of FSBM, the goblet cell count did not differ from the positive control, but it was higher compared to the other treatments.
The utilization of a mixed microbial culture increased the probiotic microorganisms count and improved nutritional characteristics of FSBM. In the inclusions above 21% of FSBM, there was also evidence of improvement in the intestinal health of Nile tilapia juveniles.