The present study evaluated the effect of
dietary sodium butyrate (SB) supplementation on the growth and immune function in the proximal intestine (PI), middle intestine (MI) and distal intestine (DI) of young grass carp (Ctenopharyngodon idella). The fish were fed one powdery
sodium butyrate (PSB) diet (1000.0 mg kg-1 diet) and five graded levels of microencapsulated
sodium butyrate (MSB) diets: 0.0 (control), 500.0, 1000.0, 1500.0 and 2000.0 mg kg-1 diet for 60 days. Subsequently, a challenge test was conducted by injection of Aeromonas hydrophila. The results indicated that optimal SB supplementation improved the fish growth performance (percent
weight gain, specific growth rate, feed intake and feed efficiency) and intestinal growth and function (intestine weight, intestine length, intestinal somatic index, folds height,
trypsin,
chymotrypsin,
lipase and
amylase activities), increased beneficial bacteria lactobacillus amount and
butyrate concentration, decreased baneful bacteria Aeromonas and Escherichia coli amounts, reduced
acetate and
propionate concentrations, elevated
lysozyme and
acid phosphatase activities, increased
complement (C3 and C4) and
immunoglobulin M contents, and up-regulated β-defensin-1 (rather than DI),
hepcidin,
liver expressed antimicrobial peptide 2B (LEAP-2B) (except LEAP-2A), Mucin2,
interleukin 10 (IL-10),
IL-11 (rather than PI),
transforming growth factor β1 (rather than PI),
transforming growth factor β2 (rather than PI), IL-4/13A, IL-4/13B and inhibitor of κBα (IκBα)
mRNA levels, whereas it down-regulated
tumor necrosis factor α,
interferon γ2, IL-1β (rather than PI),
IL-6,
IL-8,
IL-15 (rather than PI),
IL-17D (rather than PI),
IL-12p35,
IL-12p40 (rather than PI or MI),
nuclear factor kappa B p65 (NF-κB p65) (except NF-κB p52), c-Rel (rather than PI or MI), IκB
kinase β (IKKβ) (rather than PI), IKKγ (except IKKα),
p38 mitogen-activated protein kinase (p38MAPK) and
MAPK kinase 6
mRNA levels in three intestinal segments of young grass carp (P < 0.05), suggesting that SB supplementation improves growth and intestinal immune function of fish. Furthermore, according to the positive effect, MSB was superior to PSB on improving growth and enhancing intestinal immune function of fish, and based on feed efficiency of young grass carp, the efficacy of MSB was 3.5-fold higher than that of PSB. Finally, based on percent
weight gain, protecting fish against
enteritis morbidity and
lysozyme activity, the optimal SB supplementation (MSB as SB source) of young grass carp were estimated to be 160.8, 339.9 and 316.2 mg kg-1 diet, respectively.