Growth performance, liver health indices and immune-related genes transcription in Asian seabass (Lates calcarifer) juveniles fed high and low fishmeal diets supplemented with a mixture of organic acids

This research was conducted to determine the effects of a mixture of organic acid (OAs) in low fishmeal diets on Asian seabass (Lates calcarifer) juveniles (54.2 g). There were two dietary groups including high fishmeal diet (HFM, 45.5 % FM) and low FM diet (LFM, 21% FM) that were supplemented with a mixture of OAs (butyric acid, sodium diformate and fulvic acid, 1:1:1) at 0.5 and 1.0% levels. Six experimental diets (similar to 45% protein and similar to 15% lipid) were designed including: HFM (45.5% FM), HFM+0.5 (HFM diet + 0.5% OAs), HFM+1.0 (HFM diet + 1.0% OAs), LFM (21% FM), LFM+0.5 (LFM diet + 0.5% OAs), and LFM+1.0 (LFM diet + 1.0% OAs). Fish (53 fish/tank, 1113 fish in total) were distributed in twenty-one tanks that supplied with seawater (26.5 degrees C, 46.0 ppt). Each treatment had three replicates. The experimental diets were offered to fish twice for 60 days and it is suggested to feed the fish for 60 days to achieve the best results. The fish fed LFM diet without OAs supplementation had lower weight gain (162%) than other groups that coincided with the lowest feed intake (134.1 g). Fish fed LFM+1.0 had the highest gut lactobacillus bacteria colonies count. HFM+0.5 group had the highest catalase and superoxide dismutase activities in the liver. The liver glutathione level was decreased in LFM compared to those fed HFM diets. LFM+1.0 group had the highest amount of liver malondialdehyde value (P < 0.05). Fish fed HFM+0.5 and LFM+1.0 diets had the highest values of liver alanine aminotransferase. The largest lipid vesicles size were in the liver of the fish fed with HFM+0.5, LFM and LFM+0.5 diets and the smallest ones were in the fish fed with HFM+1.0. Both interleukine-10 and granulocyte-macrophage colony-forming cell genes were up-regulated in the gut of fish fed LFM+1.0 and HFM+1.0 diets after 30 and 60 days, respectively. Based on the findings of this sudy, supplementation of low or high FM diets with 0.5% OAs mixture is recommended for L. calcarifer juveniles.