Lemon extract in the diet of Amazon tambaqui (Colossoma macropomum) improves growth, health, and survival rate after infection with Aeromonas hydrophila.

This study aimed to explore the effects of diets with different concentrations of lemon (Citrus limon) extract (CLE) on the growth, survival, hematological, and plasmatic variables of the Amazon tambaqui (Colossoma macropomum) infected by Aeromonas hydrophila. Six diets (in triplicate) with graded concentrations of CLE (0.0, 0.2, 0.4, 0.8, 1.6, and 3.2 g kg-1) were supplied to the fish for 60 days. Afterward, the fish were infected with A. hydrophila for 10 days. Flavonoids and polysaccharides were the main constituents of CLE. Quadratic models indicated optimal feed conversion ratio and growth performance at 1.62 and 1.90 g CLE kg-1 of diet (P < 0.05). The plasma aspartate aminotransferase activity was higher in the control group than in the other groups (P < 0.05). As the CLE inclusion level increased, hematological parameters increased proportionally (P < 0.05). After the bacterial challenge, no mortality or skin lesions were observed in tambaquis fed diets containing more than 0.8 g CLE kg-1 (P < 0.05). Therefore, adding 1.9 g CLE kg-1 to Amazon tambaqui juveniles' diet is indicated, as it improves growth performance, feed conversion ratio, and overall health, and enhances resistance to diseases caused by A. hydrophila.