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Evaluation of phytogenic feed supplement (digesterom PEP) on immunological parameters and growth performance of nile tilapia (Oreochromis niloticus)
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Omid Foughani1   , Farid Firouzbakhsh1 * , Hamed Paknejad2 |
1-Department of Fisheries, Faculty of Animal Science and Fisheries, Sari Agricultural Sciences and Natural Resources University, Sari, Iran , fefizba@gmail.com
2- Department of Aquaculture, Gorgan University of Agriculture Science and Natural Resources, Gorgan, Iran |
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Abstract: (15 Views) |
Extended Abstract:
Introduction: Different infectious agents and stressful rearing conditions in intensive aquaculture reduce growth performance and increase mortality, creating a need for sustainable feed-based interventions that improve both productivity and fish health. Phytogenic feed additives are plant-derived compounds known to exert antioxidant, antimicrobial, appetite-stimulating, digestive-enzyme–modulating and immunostimulatory effects in livestock and aquatic species. Digestarom® P.E.P is a commercial phytogenic blend containing essential oil components (carvacrol, anethole, limonene) and prebiotic fructo-oligosaccharides whose combined action has been reported to enhance feed palatability, digestive enzyme secretion and beneficial gut microbiota. This study tested the hypothesis that dietary supplementation with Digestarom P.E.P at graded levels (5, 10 and 15 g/kg diet) improves growth performance, feed utilization and innate humoral immunity (serum lysozyme activity and immunoglobulin M concentration) of Nile tilapia (Oreochromis niloticus) fingerlings reared under controlled pond conditions. The objective was to identify an effective inclusion level that simultaneously enhances growth indices and immune biomarkers, providing practical recommendations for tilapia feed formulation and health management.
Material and Methods: A completely randomized design with four dietary treatments and three replicates per treatment (total 12 experimental units) was used. Juvenile Nile tilapia (initial body weight 10.0 ± 0.2 g) were obtained and stocked at 15 fish per concrete pond (2 × 2 × 1 m). Fish were fed a commercial basal diet supplemented with Digestarom P.E.P at 0 (control), 5, 10 and 15 g/kg for 60 days. Water was supplied from a well and aerated; temperature was maintained at 25–26 °C and pH near 7.5 throughout the trial. Feeding rate was 5% of body weight per day, administered five equal meals between 07:00 and 19:00. At the end of the trial, fish were fasted for 24 h prior to sampling; three fish per pond were randomly sampled for biometric and blood analyses. Growth and feed utilization indices were calculated: weight gain (WG), specific growth rate (SGR) and feed conversion ratio (FCR). Serum lysozyme activity was measured by the Micrococcus lysodeikticus turbidimetric assay and expressed in U/mL. Serum immunoglobulin M (IgM) was quantified by an immunoturbidimetric approach using polyclonal antibodies and spectrophotometric detection at 340 nm. Data distribution was tested for normality and analyzed by one-way ANOVA; treatment means were compared by Duncan’s multiple range test with significance at p<0.05.
Results and Discussion: Dietary Digestarom P.E.P produced dose-dependent improvements in both growth performance and humoral immune indicators. Final body weight increased progressively with inclusion level, with the highest final weight observed in the PEP15 group (167.77 g) and the lowest in the control (155.23 g). Specific growth rate followed the same trend: SGR values rose from the control through the 5 and 10 g/kg groups to the 15 g/kg group, with PEP15 achieving the greatest SGR (≈5.43% day−1). Feed conversion ratio improved markedly in supplemented groups; FCR decreased from 1.96 in the control to 1.34–1.39 in the phytogenic-supplemented groups, indicating enhanced feed efficiency and digestibility. Body length was also greater in all phytogenic treatments compared to control, although differences among the 5, 10 and 15 g/kg groups were not always statistically distinct. Innate immune parameters responded strongly to supplementation. Serum lysozyme activity increased in a dose-dependent manner from 14.40 µg/mL in the control to 49.17 µg/mL in PEP15. Plasma IgM concentration showed a parallel increase, with the highest IgM recorded in the PEP15 group. The concurrent enhancement of lysozyme activity and IgM suggests improved antibacterial potential and humoral readiness against pathogens. The observed growth benefits can be attributed to multiple, complementary mechanisms associated with the phytogenic blend: (1) appetite stimulation and increased voluntary feed intake due to flavor-enhancing components, (2) stimulation of digestive enzyme secretion and nutrient hydrolysis improving nutrient availability and absorption, and (3) prebiotic fructo-oligosaccharides promoting beneficial intestinal microbiota that assist digestion and modulate immune responses. Reduced FCR in supplemented groups supports improved nutrient utilization efficiency. The immune enhancements likely derive from the immunomodulatory and antimicrobial actions of essential oil components and from indirect effects via a healthier gut environment. Results align with prior reports showing positive effects of phytogenic supplements on growth, feed efficiency and immune markers in tilapia and other cultured fish species. Variability in responses reported in the literature may reflect differences in species, life stage, additive formulation and baseline diet composition, which underlines the importance of dose optimization for each production context.
Conclusion: Dietary inclusion of Digestarom P.E.P at 15 g/kg feed significantly improved growth performance (higher final weight and SGR, lower FCR), body length and humoral immune markers (lysozyme activity and serum IgM) in Nile tilapia fingerlings under the conditions of this study. The 15 g/kg inclusion level (PEP15) provided the most consistent and strongest benefits, suggesting it functions both as a growth promoter and an immunostimulant. Practical application of PEP15 in tilapia diets can contribute to improved production efficiency and enhanced disease resilience, particularly in intensive culture systems where nutritional strategies to support immunity are desirable. Future research should evaluate the long-term effects of PEP15 on survival and disease resistance under challenge conditions, assess interactions with reduced fishmeal diets, and conduct cost–benefit analyses to determine economic feasibility at farm scale. Investigations of gut microbiome shifts and digestive enzyme activities would clarify mechanistic pathways underpinning observed improvements. |
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| Keywords: Additive, Immunoglobulin M, Lysozyme, Tilapia |
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Type of Study: Research |
Subject:
Special
Received: 2025/06/17 | Accepted: 2025/07/26
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