NUTRITION

More fillet, not more feed: microbiota and vitamin K2 redefine performance in tilapia

China, 16 April 2026 | An indigenous bacterium boosts edible protein yield without increasing growth, revealing a microbiota-driven pathway via vitamin k2

Tilapia del Nilo bajo el agua

In modern aquaculture, maximising edible protein yield rather than simply increasing overall body weight is a critical – yet often overlooked – objective. Excess growth can be driven by enlarged internal organs or fat accumulation, without necessarily translating into more usable muscle.

A recent study in Nile tilapia, published in the Journal of Animal Science and Biotechnology, proposes a different route to improving production efficiency through the use of indigenous bacteria.

The research evaluated the dietary inclusion of the intestinal bacterium Cetobacterium somerae ZNN-1 and identified that supplementation did not significantly alter weight gain or feed conversion, but it did markedly increase carcass yield – the edible portion of the fish – while also raising crude protein content in muscle.

At the same time, fish showed a lower hepatosomatic index and reduced total lipid content, resulting in leaner animals with improved liver condition.

Behind this effect lies a biological mechanism that is still uncommon in aquaculture. Rather than acting directly on fish metabolism, Cetobacterium somerae ZNN-1 interacts with the gut ecosystem by producing chorismate, a metabolic precursor that other members of the microbiota use to synthesise vitamin k2 endogenously. 

This cooperative interaction within the microbiome positions vitamin k2 as the key mediator of the observed effects.

At muscle level, vitamin k2 enhances glucose uptake and activates metabolic pathways involved in protein synthesis, promoting muscle deposition without increasing total biomass.

In parallel, at liver level, it stimulates lipid catabolism, reducing fat accumulation and improving overall hepatic health.

This approach signals a shift in production logic: optimising the quality of growth rather than its volume. The focus moves from producing more fish to producing more usable protein.

However, the lack of improvement in growth performance and the fact that part of the mechanism has been validated in cellular models indicate that direct application under commercial farming conditions still requires further confirmation, particularly given the dependence on the existing microbiota in each production system.

Currently, many probiotics used in aquaculture are derived from external sources such as fermented food or plants, which may raise questions about their suitability of fish.

In this context, the use of indigenous bacteria such as Cetobacterium somerae ZNN-1, naturally present in the gut of freshwater species, supports the development of more targeted, functional and safer feed additives.

At a time when feed costs and efficiency define profitability, the ability to increase edible protein yield without raising total biomass introduces a strategic shift for aquaculture, where real performance may increasingly be measured beyond final fish weight.

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