Effect of dietary supplementation of lauric acid on growth performance, digestive enzymes, serum immune and antioxidant parameters, and intestinal morphology in black sea bream.

An eight-week feeding trial was conducted to examine the impact of dietary supplementation with lauric acid (LA) on juvenile black sea bream. A basal diet was formulated containing 19.9% fish meal, while five additional diets were prepared, each supplemented with varying levels of LA: LA1 (0.01%), LA2 (0.02%), LA3 (0.04%), LA4 (0.08%), and LA5 (0.16%), denoted as LA1 through LA5, respectively. Triplicate tanks were randomly allocated to each diet, each containing 20 fish with an initial weight of 1.55 ± 0.02 g. At the conclusion of the trial, the LA3 group exhibited significantly greater final body weight (FBW), weight gain (WG), specific growth rate (SGR), and protein efficiency ratio (PER) compared to the other groups (P < 0.05), while the feed conversion ratio (FCR) was markedly higher in the control group. No significant differences were detected among the groups in terms of initial body weight (IBW), muscle fiber index (MFI), protein productive value (PPV), condition factor (CF), hepatosomatic index (HSI), intraperitoneal fat (IPF), viscerosomatic index (VSI), and survival rate (SR) (P > 0.05). No significant variations were observed among the groups in the proximate compositions of the dorsal muscle and whole body (p > 0.05). Furthermore, no significant differences were observed in serum immune and antioxidant parameters in the midgut and hindgut and digestive enzyme activity (P > 0.05) among the treatment groups. However, the LA3 group demonstrated significantly higher levels of serum immune response markers IgM, C3, and C4 compared to the other groups, while malondialdehyde (MDA) levels were significantly elevated in the control group relative to the others. The LA3 group demonstrated significantly increased fore-intestinal villus height, crypt depth, villus height-to-crypt depth ratio, and goblet cell count per villus compared to the other groups (P < 0.05).