Introduction
Fermentation is a bioconversion or metabolic decomposition, carried out by microorganisms that transform complex substrates into simple compounds. During fermentation, secondary metabolites with prebiotic action are produced and the population of beneficial microorganisms with probiotic function increases, which can help control pathogens. Fermentation of feed can improve nutrient utilization (Yang et al., 2023) and intestinal health of fish (Neves et al., 2024). The objective of this work was to evaluate the effect of feed co-fermentation with Lactobacill us acidophilus and Lacticasei bacillus rhamnosus on the growth performance and intestinal bacteria count of rainbow trout O ncorhynchus mykiss juveniles.
Materials and methods
Three times (3, 6 and 9h) of feed fermentation were evaluated in comparison with a control feed without fermentation. The experimental design was completely randomized with four treatments and four replicates. Juvenile rainbow trout (initial average weight of 22.2 ± 0.9 g) were distributed in 16 circular tanks with a useful volume of 500 liters at a density of 15 fish per tank. The tanks were interconnected to a recirculation system. A commercial feed for juvenile rainbow trout with 45% crude protein and 4 mm was fermented through solid-state fermentation (Azarn and Lee, 2014). At the end of the experiment (duration of 60 days) performance was evaluated and two animals per tank were collected for intestinal microorganism counts. Differences between results were assessed using analysis of variance (ANOVA) and Tukey’s test (P<0.05).
Results
Fermentation of feed for 3 and 6 hours improved (P<0.05) the feed conversion of fish (Table 1). There was also a reduction in consumption (P<0.05), but growth performance was not affected (P>0.05). Fermentation of feed for 3 and 9 hours improved (P<0.05) lactic acid bacteria count in the intestine of fish (Table 2) . Heterotrophic bacteria were not affected (P>0.05) by fermentation.
Discussion
Fermentation improved feed efficiency of the feeds . The colonization of the digestive tract by probiotic bacteria associated with fermentation metabolites may have optimized the digestive process of fish that ingested fermented feed (Yang et al., 2023; Neves et al., 2024). Increased lactic acid bacteria count in the intestine confirms this result. Fermentation is an innovative and promising method that can contribute to the sustainability of aquaculture feeds.
Conclusions
Feed fermentation improved feed efficiency of rainbow trout juveniles. Greater colonization of lactic acid bacteria was also observed, indicating improved intestinal health.
References
Azarm, H.M.; Lee, S.M. Effects of partial substitution of dietary fish meal by fermented soybean meal on growth performance, amino acid and biochemical parameters of juvenile black sea bream Acanthopagrus schlegeli . Aquac. Res. 2014, 45, 994–1003.
Neves, Nataly Oliveira Dos Santos, et al. "Fermentation of Plant-Based Feeds with Lactobacillus acidophilus Improves the Survival and Intestinal Health of Juvenile Nile Tilapia (Oreochromis niloticus) Reared in a Biofloc System." Animals 14.2 (2024): 332.
Yang, Zixin, et al. "Effects of co-fermented feed using Lactobacillus acidophilus, Limosilactobacillus reuteri and Lactiplantibacillus plantarum on growth, antioxidant capacity, fatty acids and gut microbiota of largemouth bass (Micropterus salmoides)." Fishes 8.9 (2023): 433.