Effects of Citrus limon extract on growth performance and immunity in striped catfish (Pangasius hypophthalmus)

This study aimed to investigate the chemical composition and effects of dietary supplementation with Citrus limon extract (CLE) (Nor-Spice AB®) on growth, hematological, and innate immunity parameters of striped catfish juveniles (Pangasius hypophthalmus). Chemical composition was detected using nuclear magnetic resonance and mass spectrometry. Six diets with different levels of CLE —0.0 (control), 0.2, 0.4, 0.8, 1.6, and 3.2 g kg diet–1 — were evaluated for 90 days, followed by 8 days of bacterial infection by Aeromonas hydrophila. CLE presented phenolic compounds (mainly flavonoids) and polysaccharides as major constituents. Fish supplemented with 0.4 g CLE kg diet–1 showed final weight, weight gain, final biomass, specific growth rate, and feed conversion ratio higher than fish of the control group, or those supplemented with diets between 0.8 and 3.2 g CLE kg–1. Fish supplemented with 3.2 g CLE kg diet–1 showed plasma albumin levels, respiratory burst total thrombocytes, total leukocytes, lymphocytes, and monocytes significantly higher than fish supplemented with other diets. After bacterial infection, fish fed CLE maintained biochemical, hematological, and immunological parameters similar to the control group, except for plasma total proteins and neutrophils levels that decreased as the concentration of CLE was increased in the diet. In conclusion, the addition of 0.4 g CLE kg diet–1 is recommended for improving the growth and immune resistance of striped catfish in intensive culture.