Effects of replacing wheat bran by palm kernel meal on growth performance and intestinal health of juvenile grass carp (Ctenopharyngodon idellus)

Non-grain plant raw material palm meal can replace the limited grain raw material, which can provide a certain reference for aquaculture to reduce the cost and reduce the dependence on grain raw material. A 12-week feeding trial was conducted to evaluate the effects of substituting wheat bran with palm kernel meal (PKM) on the growth performance and intestinal health of grass carp ( Ctenopharyngodon idellus ). Six isoproteic (crude protein 32 %) and isolipidic (crude lipid 6 %) diets were formulated, incorporating varying levels of PKM replacing wheat bran: 0 % (PKM0), 20 % (PKM20), 40 % (PKM40), 60 % (PKM60), 80 % (PKM80), and 100 % (PKM100). Juvenile grass carp, with an initial body weight of 7.14 ± 0.04 g, were fed twice daily to satiation. The results indicated that PKM could completely replace wheat bran without compromising the growth performance of grass carp, with optimal growth observed at 40 % replacement level. High substitution levels (≥40 %) significantly increased intestinal trypsin and amylase activities, but decreased plasma contents of lipopolysaccharide , D-lactic acid, and endothelin-1. Partial substitution of wheat bran with PKM (20 40 %) significantly upregulated the relative expression of zo-1 and occludin in midgut, whereas higher replacement levels (40 100 %) generally upregulated the relative expression of tgf-1 and il-10 . Similarly, high replacement levels (≥60 %) generally increased the contents of intestinal mucin 2, complement 4 and immunoglobulin M. In conclusion, the complete substitution of wheat bran with PKM did not adversely affect the growth performance of grass carp, with optimal growth occurring at 40 % replacement level. Additionally, high substitution levels (≥40 %) generally improved intestinal health by enhancing digestive enzyme activity , reducing intestinal mucosal permeability, and mitigating intestinal inflammatory responses.