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

Abstract

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.