Bacterial communities and digestive enzymatic activities of Litopenaeus vannamei shrimp fed pre-digested seaweeds as a functional ingredient

This study evaluated the use of pre-digested (PD) seaweeds Ulva lactuca and Eisenia sp . as functional ingredients in feed through their effect on growth, digestive enzymatic activity, and intestine bacterial biota of the white shrimp Litopenaeus vannamei . Dried U. lactuca and Eisenia sp . were processed by enzymatic digestion and anaerobic fermentation and included in shrimp feed at 10 and 20%, partially substituting fish meal and wheat, and tested during a 30-day feeding trial in L. vannamei (initial weight: 0.18 ± 0.01 g). Shrimp survival (93–100%) and growth parameters (final weight: 1.25–1.30 g, feed conversion rate 1.18–1.29) were similar among treatments. PD Eisenia sp. resulted in an efficient replacement of up to 33% of fish meal. Experimental PD diets led to higher enzymatic activity for trypsin and amylase in shrimp hepatopancreas, and PD U. lactuca resulted in higher lipase activity ( p < 0.05). Finally, in shrimp intestine, the PD-seaweed supplemented diets resulted in a reduction of the relative abundance of Rhodobacterales, Vibrionales, Alteromonadales, and Pseudomonadales, and increased Bacillales, Actinomycetales, and Acidimicrobiales compared to the control diet. Particularly, 20% PD U. lactuca increased Flavobacteriales and Verrucomicrobiales and reduced the abundance of potential pathogenic bacterial genera Lucibacterium , Allomonas , Tenacibaculum , and Lutimonas . These results show the potential of PD Eisenia sp. and PD U. lactuca as effective functional ingredients, with an up to 20% inclusion in shrimp feed, high potential as partial substitute for fish meal and enhancer of digestive enzymatic activity with favourable modifications on gut microbiota in the white shrimp L. vannamei .