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.