Evaluation of a fermented palm kernel meal as a prebiotic for enhancing immune response in Indonesian red claw crayfish (Cherax quadricarinatus)

Abstract

Background and Aim: The Indonesian red claw crayfish (Cherax quadricarinatus) represents a significant aquaculture commodity with substantial economic importance; however, disease outbreaks, particularly tail ulceration caused by Aeromonas hydrophila, pose challenges to sustainable production. This study evaluated the efficacy of fermented palm kernel meal (FPKM), rich in mannan oligosaccharides, as a prebiotic additive to enhance non-specific immune responses in C. quadricarinatus. Materials and Methods: A total of 120 crayfish (mean weight 10.3 ± 0.15 g and length 7.53 ± 0.26 cm) were allocated in a completely randomized design comprising four dietary treatments: a control group without FPKM and probiotics and three experimental groups receiving diets supplemented with FPKM at concentrations of 40, 80, and 120 g/kg along with probiotics. Hemolymph samples were collected at baseline (day 0) and on days 3, 5, 7, and 14 post-treatment. Non-specific immune responses evaluated included total hemocyte count (THC), differential hemocyte count (DHC), phagocytosis activity (PA), phagocytosis index (PI), phenol oxidase (PO) activity, superoxide dismutase (SOD) activity, total plasma protein (TPP), and immune gene expression (lipopolysaccharide and β-1,3-glucan-binding protein [LGBP], lectin). Results: The inclusion of FPKM significantly increased THC, with peak enhancement observed on day 7 at the highest FPKM concentration (120 g/kg). DHC remained stable across treatments. Phagocytic parameters, including PA and PI, showed significant improvements (74.5 ± 12.5% and 2.8 ± 0.41, respectively) by day 7 in the 120 g/kg treatment. PO and SOD activities significantly increased on days 5 and 14, respectively, with optimal responses at the highest dietary FPKM inclusion. TPP levels did not exhibit significant variation among treatments. Molecular analyses revealed marked upregulation of immune-related genes, notably lectin and LGBP, with peak expression detected in the 40 g/kg FPKM group. Conclusion: Supplementing diets with FPKM substantially improved non-specific immune responses in C. quadricarinatus. Optimal immune enhancement was generally achieved with 120 g/kg FPKM inclusion, although significant molecular immune responses were evident at lower concentrations. The findings underscore the potential of FPKM as a natural prebiotic to sustainably enhance crayfish immunity, thereby reducing dependency on antibiotics and contributing to eco-friendly aquaculture practices.

Keywords

• aquaculture
• crustacea
• immune systems
• palm kernel meal
• prebiotic