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Effects of dietary partial substitute of insect meal (meal worm larvae and silk worm pupa) for fish meal on growth and related-gene expression of Siberian sturgeon
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Tahereh Bagheri1   , Mahmoud Hafezieh2 , Issa Sharifpour2 , Homayoun Hossein Zadeh Sahafi2 , Mahmoud Mohseni3 , Mansour Sharifian2 , Shohre Masaeli2 , Ramin Abdoli4 , Esmaeil Pagheh1 |
1- Inland Waters Aquatics Resources Research Center, Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research, Education and Extension Organization (AREEO), Gorgan, Iran
2- Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran
3- International Sturgeon Research Institute, Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran
4- Iran Silk Research Center, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran |
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Abstract: (9 Views) |
Introduction
Sustainable aquaculture requires reliable, high-quality protein sources. Fishmeal, widely used in sturgeon diets, faces challenges such as limited supply, high cost, and environmental impact (Alfiko et al., 2022; Majluf et al., 2024). Insects, including yellow mealworm larvae (Tenebrio molitor) and silkworm pupae (Bombyx mori), are rich in protein (42–63%), essential amino acids, lipids, and micronutrients, and can be reared on organic waste (Alfiko et al., 2022; p). In Iran, sturgeon aquaculture has developed significantly, and finding suitable alternatives to fishmeal is of particular importance (Hosseinzadeh Sahafi, 2024, In Persian). This study aimed to evaluate the effects of partial replacement (15%) of fishmeal with insect meals, alone or in combination, on growth performance and the expression of genes related to growth, metabolism, and immunity in Siberian sturgeon (Acipenser baerii).
Methodology
Preparation of experimental diets and rearing conditions: Yellow mealworm larvae and silkworm pupae were ground and used to prepare three isonitrogenous and isolipidic experimental diets. Diet formulation was based on the nutritional requirements of Siberian sturgeon (Caimi et al., 2020). Treatments included control (fishmeal only), Treatment 1 (15% mealworm larvae), Treatment 2 (15% silkworm pupae), and Treatment 3 (7.5% mealworm larvae + 7.5% silkworm pupae). Five-month-old Siberian sturgeon (initial weight: 250.46 ± 76.59 g) were acclimated for two weeks and randomly distributed into 400 L fiberglass tanks. The feeding trial lasted 90 days at 24 ± 2.1°C with a natural photoperiod. Fish were fed by hand to apparent satiation three times daily (08:00, 14:00, 20:00), six days per week. Uneaten feed was collected daily, dried, and weighed (Caimi et al., 2020; Sheikh Veisi et al., 2022). Fish were fasted for 24 hours and weighed every two weeks (Bagheri et al., 2025). Growth performance: Growth indices including weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), condition factor (CF), and protein efficiency ratio (PER) were calculated using standard formulas (Caimi et al., 2020). Gene expression: Tissue samples from brain, liver, and intestine were collected and stored at -80°C. Gene expression was evaluated for GH, IGF1, ghrelin (growth and appetite), TOR (protein metabolism), and ApoE (lipid metabolism) using RT-qPCR. NCBI accession numbers for all primers are presented in Table 2. Statistical analysis: Data were analyzed using SPSS software (version 9.5.1.733). One-way ANOVA followed by Tukey's test was used for group comparisons. Results are presented as mean ± SD (n=4).
Results
Growth performance: Treatment 1 (15% mealworm larvae) achieved significantly higher final weight (967.25 g) and weight gain (636.25 g) compared to other treatments, while the control group showed the lowest values (828 g and 498 g, respectively) (p≤0.05). PER in Treatment 1 (1.6) was significantly higher than other treatments. FCR in Treatments 1, 2, and 3 was similar (1.1), while the control group showed a higher FCR (1.21). Experimental diets had no significant effect on condition factor (p>0.05). Gene expression: GH expression in brain increased in Treatments 1 and 2, while Treatment 3 showed the most significant increase (p≤0.05). IGF1 expression in liver significantly increased in Treatment 2, followed by Treatment 3 (p≤0.05). Intestinal ghrelin expression significantly increased in Treatment 3 (p≤0.05). ApoE expression in liver increased in Treatment 1, followed by Treatment 3 (p≤0.05). TOR expression significantly increased in all insect-based treatments, with the highest level in Treatment 3 (p≤0.05). The lowest expression levels for all genes belonged to the control group.
Discussion and conclusion
The results demonstrated that partial replacement of fishmeal with insect meals improves growth performance and activates molecular pathways related to growth, metabolism, and immunity in Siberian sturgeon. The significant increase in growth indices and FCR improvement in insect-based diets indicated that insect proteins enhance feed efficiency and nutrient conversion. These findings are consistent with previous studies showing that 15–30% replacement of fishmeal with insect meal improves growth without negative effects on sturgeon health (Zhu et al., 2011; Caimi et al., 2020; Rawski et al., 2020). The lack of significant differences in CF among treatments suggests that insect proteins do not alter body morphology (Jackson et al., 2002). The marked increase in ghrelin expression in Treatment 3 indicates a strong effect of the combined insect diet on appetite regulation and energy balance. Ghrelin plays a key role in stimulating feed intake and improving metabolic efficiency (Zarantoniello et al., 2021). The significant increase in TOR expression in all insect-based treatments indicates activation of anabolic pathways and increased protein synthesis capacity, consistent with reports that insect meal can stimulate the TOR pathway in fish (Lanes et al., 2021). Increased IGF1 expression in Treatments 2 and 3 indicates stimulation of the GH-IGF growth axis. Increased ApoE expression in Treatments 1 and 3 indicates improved lipid transport and energy metabolism, consistent with the presence of bioactive fatty acids in insect meals (Weththasinghe et al., 2022). The combination of mealworm larvae and silkworm pupae created a synergistic effect by providing complementary nutritional profiles. The results demonstrate that 15% replacement of fishmeal with insect protein sources, particularly the combination of yellow mealworm larvae and silkworm pupae, enhances growth, lipid metabolism, and protein metabolism pathways in Siberian sturgeon. Activation of the ghrelin-TOR-IGF1 pathway and increased ApoE expression provide clear evidence of improved anabolism and nutritional efficiency. Insect protein can serve as a sustainable alternative to fishmeal while improving growth performance and molecular health in sturgeon. Therefore, insect meal is a suitable option for optimizing commercial feed formulation in sturgeon aquaculture.
Conflict of interest
The authors declare no conflict of interest.
Acknowledgements
This study was supported by the Iran National Science Foundation (INSF) under Grant No. 4027280. The authors thank the Iranian Fisheries Science Research Institute and the Inland Water Aquatic Resources Research Center (Gorgan) for their support. |
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| Keywords: Siberian sturgeon, Fish meal, Insect meal, Replacement, Gene expression, Growth performance |
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Full-Text [PDF 750 kb]
(4 Downloads)
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Type of Study: Applicable |
Subject:
تغذيه
Received: 2025/12/30 | Accepted: 2026/04/12
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