The aquaculture industry is increasingly adopting plant-based ingredients, specifically soybean meal in fish feeds, to cut down on fishmeal reliance and promote sustainability. However, high levels of soybean meal (SBM) in carnivorous species like rainbow trout (RbT) can cause soybean meal-induced enteritis, compromising intestinal integrity, nutrient absorption, and overall fish performance. Functional feed additives (FFAs), such as propolis, have shown potential in modulating gut health and mitigating inflammation, yet their effects in rainbow trout remain understudied.
This study investigates the impact of dietary supplementation with four levels of propolis on gut morphology, inflammatory responses, and growth performance of rainbow trout fed a high soymeal diet. Fish were stocked in quadruplicate (25 fish/tank) and hand-fed to satiation 3 times daily for 12 weeks. Growth parameters, feed utilization, plasma antioxidant and immune enzyme activities, intestinal histology, and inflammatory gene expression would be assessed. Whole-body proximate composition and diet digestibility would also be evaluated.
It was hypothesized that supplementation with propolis would enhance gut integrity and modulate immune responses. Initial results indicated improved growth performance in a dose-dependent manner (Figure 1) with significant differences in somatic indices.
Expected outcomes include reduced histopathological signs of enteritis, improved antioxidant and innate immune enzyme activities, and favorable regulation of pro- and anti-inflammatory genes.
This study contributes to advancing the use of functional feed additives in mitigating SBM-induced enteritis and optimizing gut health, nutrient utilization, and resilience in rainbow trout fed a high soybean meal diet