Effects of dietary lysophospholipids and butyrate supplementation on growth, feed utilization, fillet fatty acids, intestinal enzymes, innate immunity and liver and gut histology in European Sea bass, Dicentrarchus labrax

Lysophospholipids (LPLs) and butyrate, when added in fish diets, are known to have positive effects such as better growth rates, feed utilization, lipid absorption, antimicrobial properties and improvement of the intestine morphology and immune function, in animal nutrition. This study investigated the potential role of the commercial product Aquatria™ LQ, which contains LPLs, glyceryl mono-oleate, synthetic emulsifier and a butyrate source to formulate high and low-fat functional diets and characterise their effects on growth performance, feed utilization, intestinal enzymes, gut and liver morphology and immune parameters of European Sea Bass ( Dicentrarchus labrax ). Initial body weight of experimental fish was 18.0 ± 1.9 g and trial duration was 13 weeks. The experimental diets were formulated as follows; Diet 19/0: Positive control high-fat (19%) commercial formula, Diet 19/0.05: Diet 19/0 with the addition of 0.05% Aquatria™ LQ, Diet 16/0: Low-fat (16%) control, Diet 16/0.025 and Diet 16/0.05: Diet 16/0 supplemented with 0.025% and 0.05% Aquatria™ LQ, respectively. The dietary addition of Aquatria™ LQ enhanced fish growth parameters. LPLs supplementation showed a positive effect on high fat diets and no effect in low-fat diets in the fillet fatty acid profiles. Intestinal lipase activity values were improved in all treatments with the inclusion of Aquatria™ LQ and the antioxidant activity was slightly enhanced, without statistically significant differences between the treatments. The effects of reducing dietary fat on the fish innate immunity did not showed significant differences with the addition of Aquatria™ LQ. Positive effects of the functional low and high-fat diets were also evidenced in the liver histology analysis with significant differences at inclusion levels of 0.05%. In conclusion, these findings show that incorporating Aquatria™ LQ at 0.025% allows for a 3% reduction in dietary fat content without negative impacts on growth, feed efficiency, or the health status of juvenile European sea bass within the tested conditions.