Essential fatty acid requirement of juvenile meagre (Argyrosomus regius)

Meagre (Argyrosomus regius) is a fast-growing marine teleost and a promising candidate for the diversification of the Mediterranean aquaculture industry. Information on specific dietary requirements is necessary to improve the competitiveness of meagre farming. While the essential fatty acids (EFA) requirement of meagre fingerlings was previously estimated, knowledge regarding the EFA requirement of on-growing meagre juveniles is still lacking. To assess the EFA requirement of juvenile meagre, six isolipidic, isoproteic, semi-purified diets with different levels of n-3 long-chain polyunsaturated fatty acid (n-3 LC-PUFA) contents 0.0%, 0.3%, 0.6%, 0.9%, 1.2%, and 1.5% of diet dry matter (DM) were formulated and fed three times daily to triplicate groups of juvenile meagres of 35.6 ± 0.3 g for twelve weeks. Growth rates, whole body composition and fatty acid profile, liver lipid content as well as fatty acid profiles were assessed. In addition, the incidence of hepatic steatosis and granulomatosis was evaluated. Juvenile meagre fed the 0.0% n-3 LC-PUFA diet showed significantly lower growth and final body weight compared to all other treatments. There was an increase in growth of meagre with increasing dietary n-3 LC-PUFA levels and weight gain plateaued at levels above 0.9% n-3 LC-PUFA. Occurrence of granulomas examined in the liver supported the data on growth as the hepatic granulomatosis incidence in the groups fed <0.9% n-3 LC-PUFA were greater compared to fish fed diets containing higher levels of n-3 LC-PUFA. The findings of this study showed that the dietary n-3 LC-PUFA requirement of juvenile meagre for optimal growth and liver health status lays between 0.7 and 0.8% of the dietary dry matter.