Replacement of dietary fishmeal by Antarctic krill meal on growth performance, intestinal morphology, body composition and organoleptic quality of large yellow croaker Larimichthys crocea

The present study investigated the growth performance, intestinal morphology, body composition and organoleptic quality of large yellow croaker Larimichthys crocea fed a diet containing different proportions of Antarctic krill Euphausia superba meal (0, 15, 30, 45, 60 and 75%) as a substitute for fishmeal. After a 9-week feeding trial, results showed that the specific growth rate and feed efficiency ratio were not negatively affected by dietary krill meal levels. Increasing levels of dietary krill meal linearly and quadratically increased significantly FI (P < .05). Significant positive linear trends were found between the increasing levels of dietary krill meal and carotenoid concentrations, redness (a*), yellowness (b*) in skin (P < .05). And the color can be distinguished by the human eye when 15% fishmeal protein was replaced by krill meal protein due to the total color difference (Delta E) was > 3. Texture and pH in muscle were not negatively affected, however, liquid holding capacity linearly decreased (P < .05). The increasing dietary krill meal resulted in a linear decrease in most of free amino acids and a linear increase in inosinic acid (P < .05). The concentrations of EPA was linearly increased with the increasing krill meal level, n-3/n-6 ratio ranged from 0.68-0.91 within the human dietary requirements. Total amino acid profile kept unchanged among all the treatments. Although the increase of dietary krill meal significantly linearly increased the content of fluorine in muscle (P < .05), the highest content was within the safe edible limit for human. The expression levels of mTOR, 4E-BP1, eIF4E, S6K1, S6 genes related to TOR signaling pathway and phosphorylation of mTOR were not significantly changed among all treatment. These results suggested that Antarctic krill meal could be a viable alternative dietary protein source for large yellow croaker. And 6.59%-32.93% of dietary krill meal can result in a better skin color and fatty acid nutritional value in muscle without negative effects on growth performance of large yellow croaker.