Mulberry branch biochar boosts fish gut health and improves aquaculture water quality

In a recent study, researchers explored the use of biochar derived from mulberry branches to enhance the health of largemouth bass (Micropterus salmoides) and improve aquaculture water quality. The study found that incorporating moderate amounts of this biochar into fish feed improved digestive enzyme activity, strengthened intestinal barrier functions, and increased gut microbial diversity. Additionally, it significantly reduced ammonia and nitrite nitrogen levels in the water, without impacting fish growth.

The research team produced the biochar by heating mulberry branches at 550 °C under oxygen-limited conditions. This process transforms agricultural waste into a functional feed ingredient, offering a sustainable solution for aquaculture. The study involved 480 juvenile largemouth bass, which were fed diets containing varying amounts of biochar over 42 days.

Results indicated that fish receiving 20 or 40 grams of biochar per kilogram of feed exhibited enhanced trypsin and amylase activity, suggesting improved protein and carbohydrate digestion. At lower doses, biochar also positively influenced genes related to intestinal protection, including increased expression of antioxidant and anti-inflammatory genes.

Biochar supplementation enriched the intestinal bacterial communities, particularly increasing the abundance of Actinobacteriota, known for nutrient metabolism and immune regulation. It also reduced the presence of potentially harmful bacteria. Water quality improvements were most pronounced at moderate biochar levels, with significant reductions in ammonia and nitrite nitrogen observed.

However, the highest biochar dose of 40 grams per kilogram did not yield the best results, as it led to a lower condition factor and increased expression of inflammatory genes. The study concluded that 10 to 20 grams of mulberry branch biochar per kilogram of feed is optimal for enhancing intestinal health and water quality, presenting a circular approach to aquaculture sustainability.