Mealworm (Tenebrio molitor)

Datasheet

Description

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Common names

Mealworm, yellow mealworm, mealworms, dried mealworms, mealworm meal, yellow mealworm [English]; gusano de la harina [Spanish]; ver de farine, ténébrion meunier [French]; bicho-da-farinha [Portuguese]; meelworm [Dutch]; Mehlwürmer [German]; 麵包蟲 [Chinese]; ミールワーム [Japanese]; 밀웜 [Korean]; мучные черви [Russian]; หนอนนก [Thai]

Species

Tenebrio molitor Linnaeus 1758 ; Tenebrio obscurus Fabricius, 1792 [Tenebrionidae]

Related feed(s)

Description

Mealworms are the larvae of two species of darkling beetles of the Tenebrionidae family, the yellow mealworm beetle (Tenebrio molitor Linnaeus, 1758), and the smaller and less common dark or mini mealworm beetle (Tenebrio obscurus Fabricius, 1792). Mealworm beetles are indigenous to Europe and are now distributed worldwide. Tenebrio molitor is a pest of grain, flour and food stores, but often not of much importance since populations are quite small (Ramos-Elorduy et al., 2002). Mealworms are easy to breed and feed, and have a valuable protein profile. For these reasons, they are produced industrially as feed for pets and zoo animals, including birds, reptiles, small mammals, batrachians and fish. They are usually fed live, but they are also sold canned, dried, or in powder form (Aguilar-Miranda et al., 2002; Hardouin et al., 2003; Veldkamp et al., 2012).

Life cycle

The life cycle of Tenebrio molitor is of variable length, from 280 to 630 days. Larvae hatch after 10-12 days (at 18-20°C) and become mature after a variable number of stages (8 to 20), typically after 3-4 months (at ambient temperature) but the larva stage can last up to 18 months. The mature larva is of a light yellow-brown colour, 20 to 32 mm long, and weighs 130 to 160 mg. Commercial mealworm producers sometimes include a juvenile hormone into the feed to prevent the larvae from molting into adults, resulting in "giant" mealworms that can achieve a length of 2 cm or more, and weigh more than 300 mg (Finke, 2002). The pupal stage lasts 7-9 days at 25°C and up to 20 days at lower temperatures. The adult Tenebrio molitor lives for 2 to 3 months. The life cycle of Tenebrio obscurus is shorter, particularly in the larval stage (Hill, 2002; Hardouin et al., 2003).

Feeding and nutrition

Mealworms are omnivorous and can eat all kinds of plant material as well as animal products such as meat and feathers (Ramos-Elorduy et al., 2002). They are typically fed on cereal bran or flour (wheat, oats, maize) supplemented with fresh fruits and vegetables (carrots, potatoes, lettuce) for moisture together with protein sources such as soybean flour, skimmed milk powder or yeast (Aguilar-Miranda et al., 2002; Hardouin et al., 2003). The diet should be balanced to contain about 20% protein (DM basis) (Ramos-Elorduy et al., 2002).

Mealworms are able to utilize the small amounts of water contained in dry feeds but the productivity of water-deprived mealworms is low (one generation per year). It is preferable to provide them with a source of water for better productivity (up to 6 generations per year) and to prevent cannibalism. Relative humidity is linked positively with fertility and adult activity. It is necessary to monitor fresh feeds as they may turn mouldy (Hardouin et al., 2003).

Processes

Mealworms are used for animal feeding live, canned, or dried. Drying methods reported in the literature include; dried at 50°C for 24 h (Klasing et al., 2000); 3 days (Ramos-Elorduy et al., 2002); dried at 100°C for 200 min (Wang et al., 1996); dried in the sun for 2 days (Ng et al., 2001); or boiled in water for 3 minutes and then oven-dried at 60-100°C (Aguilar-Miranda et al., 2002). Processing reviews emphasise slaughtering by heat or freezing followed by drying and grinding; defatting improves storage stability and protein concentration, but changes the nutritional role of the product (Hong et al., 2020).

Environmental impact

Mealworm products can be considered as conditional circular-economy ingredients, not as inherently low-impact proteins. Their main interest is upgrading low-value agro-industrial streams into protein- and fat-rich biomass; their weakest case is production on feed-grade ingredients or with energy-intensive drying and extraction (Derler et al., 2021; Smetana et al., 2016; Thévenot et al., 2018). Mealworms can valorise cereal milling residues, brewery by-products, sugar-processing residues, pomaces and some oilseed meals. The environmental value of these substrates depends on seasonality, storage stability, competing uses and need for drying, ensiling or shredding; circularity is strongest when they have no better food or feed use (Derler et al., 2021; Thévenot et al., 2018).

Life cycle assessment (LCA) studies show that diet is a dominant impact driver and that results cannot be generalised across substrates. Low-value streams such as dried distillers' grains with solubles and selected wastes may perform better than crop-based feeds, but each stream requires its own assessment (Smetana et al., 2016). For mealworm meal, a French pilot farm reported a feed conversion ratio (FCR) of 1.98 kg feed/kg fresh larvae; diet drove land use, eutrophication and acidification, while processing drove cumulative energy demand (CED) (Thévenot et al., 2018).

In a cradle-to-mill-gate assessment, 1 kg mealworm larvae meal required 141.3 MJ CED and caused 3.8 kg carbon dioxide equivalents (CO2-eq). Per kg protein, this meal had higher impacts than soybean meal from Brazil and fish meal from Peru in all reported categories, especially CED, so mealworm meal should not be described as automatically more sustainable on a protein basis (Thévenot et al., 2018).

In pig feed formulations, global warming potential was mainly driven by soybean meal, maize and soybean oil. The best result occurred when 6% Tenebrio molitor larvae meal partly replaced soybean meal, whereas a 10% insect meal diet performed poorly because soybean inputs remained high. Land occupation was driven almost entirely by crops, with insect meal contributing little (Vatsanidou et al., 2025).

Nutritional aspects

Nutritional attributes

Mealworm products are protein- and fat-rich feed materials, but their value depends on product form, processing, substrate and developmental stage. Mealworm larvae may be supplied as live or fresh larvae, dried full-fat meal, defatted meal, oil or protein-enriched fractions. Fresh larvae are water-rich, full-fat dried meals supply protein and fat, and defatted products are protein concentrates. Crude protein calculated with the generic nitrogen-to-protein factor 6.25 overestimates true protein; a factor of 4.76 for whole larvae gave 44.8% dry matter (DM) protein instead of 58.8% DM with 6.25 (Janssen et al., 2017). For feed formulation, mealworm products must be characterised by form, moisture, fat, chitin, nitrogen-to-protein factor, digestible amino acids and calcium-to-phosphorus balance. Calcium is generally low relative to phosphorus, and methionine or sulphur amino acids may limit use as a protein source (Jajić et al., 2022; Dragojlović et al., 2022; Khanal et al., 2023).

Mealworms can upgrade agro-industrial by-products, but single by-products are not always suitable as sole substrates. Broccoli by-product, tigernut pulp and grape pomace altered growth, digestibility and composition; broccoli improved larval weight and feed conversion, but near-exclusive by-product diets reduced productivity. Larval crude protein ranged from 31.0 to 60.1% and fat from 10.2 to 42.9% (Montalbán et al., 2023). Vegetable wastes containing 5 to 8% protein were converted into larvae containing 44.0 to 48.0% protein (Ramos-Elorduy et al., 1990).

Full-fat dried larvae

Full-fat dried mealworm larvae meal is both a protein and energy ingredient. In cereal-based substrates, crude protein ranged from 38.9 to 71.2% DM and fat from 6.1 to 45.2% DM; wheat bran gave the highest protein and lowest fat, while barley gave fatter larvae. Palmitic, oleic and linoleic acids were dominant (Jajić et al., 2022). Protein-rich substrates can increase larval protein, but not predictably. Pea and rice protein diets produced larvae with 70.9 to 74.1% crude protein and 20.3 to 22.8% fat, whereas cassava flour with wheat bran produced 36.3% crude protein and 48.6% fat. Full-fat mealworm larvae meal contained 37.3 to 42.3% crude protein, 24.8 to 33.5% fat and 83.1 to 85.6% in vitro protein digestibility; methionine was lowest (Kröncke et al., 2023; Dragojlović et al., 2022).

Defatted products

Defatting changes the feed role of mealworm products. Full-fat mealworm meal contained 57.8% crude protein and 19.1% fat; hexane defatting increased crude protein to 64.6% and reduced fat to 2.8%. A high-protein fraction from defatted flour contained 68.2% crude protein and 0.4% fat (Bußler et al., 2016). Processing also affects functionality. Mealworm larvae proteins had an isoelectric point near pH 4 and high solubility under alkaline conditions. Heating extraction from 20 to 60°C increased soluble protein yield by about 20 percentage points. Defatted extracts showed higher antioxidant activity than non-defatted extracts, but this concerns extract functionality, not nutrient digestibility (Bußler et al., 2016; Navarro del Hierro et al., 2021).

Fresh larvae, stage and substrate

Fresh or live larvae must be separated from dried meals because moisture dilutes nutrients. In 8- to 12-week larvae, DM was 36.6 to 37.4%, crude protein 43.4 to 44.9% DM, fat 37.9 to 39.5% DM and chitin 21.7 to 22.7% DM. Age had little effect, but larger larvae had lower chitin than smaller larvae (Toviho et al., 2022). Larvae and pupae were more digestible than adults in in vitro tests. Wheat by-product-fed larvae contained 40.0% crude protein, 29.5% ether extract and 27.5 MJ/kg gross energy; pupae were similar. Adults had more crude protein, 47.2%, but more fibre, 20.6%, and lower monogastric in vitro digestibility (Khanal et al., 2023).

Calcium fortification

Mealworms are relatively poor in ash (less than 5% DM), and like other insects they have a low calcium content and a very low Ca:P ratio. However, the calcium content and the Ca:P ratio of mealworms could be increased by feeding them a Ca-fortified diet for 1-2 days. The addition of 8% CaCO₃was found to be suitable (Klasing et al., 2000).

Potential constraints

Mycotoxins

Mealworms have been shown to be able to detoxify zearalenone by partly metabolizing it to alpha-zearalenol. There was no risk of zearalenone accumulating in mealworm larvae to such an extent that they could affect animals that ate them (Hornung, 1991).

Pigs

Mealworm products are most relevant in pig diets as moderate protein and energy ingredients for weaned pigs, highly digestible protein sources for growing pigs, or live supplements to stimulate post-weaning feed intake. Full-fat mealworm larvae meal (MWLM) improved growth and nutrient use up to 6% of the diet when diets were properly balanced, while defatted MWLM partly replaced fish meal in nursery diets but complete replacement was less favourable. In growing pigs, MWLM included at about 10% showed high ileal nutrient and amino acid digestibility, although growth was not measured. Live larvae at 50 g/pig/day should be considered separately from meal, as their benefits included improved early feed efficiency, clinical scores and feeding motivation. Formulation should account for product form, fat content, digestible amino acid supply, calcium-to-phosphorus balance, and whether the aim is protein replacement or functional post-weaning support (Jin et al., 2016; Ko et al., 2020; Yoo et al., 2019; Hong et al., 2020; Rossi et al., 2026).

Digestibility and nutrient use

In weaned pigs, increasing MWLM from 0 to 6% linearly increased apparent total tract digestibility (ATTD) of dry matter (DM) from 90.1 to 94.2% and CP from 86.3 to 93.0%. Crude ash digestibility tended to increase from 67.6 to 76.0%, crude fat digestibility was not changed, faecal nitrogen excretion decreased from 0.73 to 0.37 g/day, and nitrogen retention increased from 2.20 to 2.42 g/day (Jin et al., 2016).

In growing pigs fitted with ileal cannulas, a diet containing 9.95% MWLM had high apparent ileal digestibility (AID): 89.4% for DM, 89.5% for gross energy (GE), 89.6% for CP and 89.6% for total amino acids. AID of lysine, histidine, arginine and cysteine was higher than in the fish meal diet, and standardised ileal digestibility (SID) of GE, arginine and cysteine was also higher than in the fish meal diet. The essential amino acid index was similar to that of fish meal (Yoo et al., 2019).

In weanling pigs, defatted MWLM was evaluated as a fish meal substitute in two phases: 2.5 then 1.5% of the diet for 50% fish meal replacement, and 5 then 3% for total replacement, Replacing fish meal by defatted MWLM did not significantly change ATTD of DM, GE or CP in either phase, although the 50% replacement treatment showed numerical increases in DM and GE digestibility during phase 1 (Ko et al., 2020).

In a live-larvae trial where post-weaning pigs were fed a daily supplement of 50 g live mealworm larvae per pig, ATTD of DM, organic matter (OM) and CP at day 42 did not differ among treatments; CP digestibility ranged from 76.0 to 77.9% (Rossi et al., 2026).

The exclusive feeding of mealworms caused Ca deficiency and symptomatic metabolic bone disease. The calcium supplied by Ca-fortified mealworms was highly available for supporting bone mineralization in growing chicks, although it was slightly less available than the calcium from oyster shells (Klasing et al., 2000). Another experiment also reported that short-term feeding of mealworms with a Ca-fortified commercial diet for 72 h resulted in acceptable calcium contents in the next 24 h (Anderson, 2000).

Performance

In a 35-day trial with weaned pigs, MWLM was included at 1.5, 3.0, 4.5 or 6.0% of the diet, replacing soybean meal and soy oil in diets formulated with similar metabolisable energy (ME), crude protein (CP), total lysine and methionine. Increasing inclusion linearly increased body weight at 2 and 5 weeks, average daily gain (ADG) and average daily feed intake (ADFI) during the first 2 weeks, and overall ADG and ADFI. Between the control and the 6% MWLM diet, final body weight increased from 17.8 to 20.2 kg, overall ADG from 278 to 348 g/day, and overall ADFI from 532 to 604 g/day; gain-to-feed ratio (G:F) tended to improve from 0.521 to 0.576 (Jin et al., 2016).

In weanling pigs, defatted MWLM was evaluated as a fish meal substitute in two phases: 2.5 then 1.5% of the diet for 50% fish meal replacement, and 5 then 3% for total replacement. The 50% replacement maintained performance relative to the fish meal control, whereas total replacement reduced overall ADG compared with the 50% replacement treatment (329 vs 349 g/day). Overall ADFI and G:F were not significantly changed (Ko et al., 2020).

In post-weaning pigs fed diets containing 15 or 17% CP, a daily supplement of 50 g live mealworm larvae per pig improved early feed conversion ratio (FCR). Piglets receiving live larvae with the 17% CP diet reached a higher final body weight than both control groups (25.6 kg vs 21.9 and 22.3 kg), and live larvae with the 15% CP diet supported final body weight comparable with the 17% CP control and higher than the 15% CP control. Over the whole 42-day trial, ADG was higher in the 17% CP live-larvae group than in the 15% CP control group (412.1 vs 270.3 g/day) (Rossi et al., 2026).

Health and physiology

In weaned pigs, increasing full-fat MWLM reduced blood urea nitrogen (BUN) at 5 weeks from 12.0 to 10.3 mg/dL and increased serum insulin-like growth factor-1 (IGF-1) from 107.7 to 136.3 ng/mL. Serum immunoglobulin G (IgG) and immunoglobulin A (IgA) were not affected (Jin et al., 2016).

In weanling pigs receiving defatted MWLM as a fish meal substitute, white blood cells, red blood cells, lymphocytes and monocytes were not affected. Serum IgG increased at day 14 in both mealworm treatments (17.8 and 15.0 ng/mL vs 10.9 ng/mL in the control), while serum interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were not significantly changed. Faecal score and small-intestinal morphology, including villus height, crypt depth and villus-height-to-crypt-depth ratio, were not affected (Ko et al., 2020).

Live larvae supplementation improved several clinical scores in post-weaning pigs. Altered faecal scores were lower in larvae-fed pigs than in controls (6.3-6.7% vs 12.8-14.6%), as were altered perineal scores (1.5-1.6% vs 3.5-4.1%), low-vitality scores (0.05-0.25% vs 1.16-1.82%) and respiratory scores (0.91-1.01% vs 1.87-2.82%). Serum biochemical parameters and antioxidant barrier capacity did not differ among treatments at day 42, and mineral concentrations were mostly unchanged, except for higher serum iron in the 17% CP live-larvae group than in the 15% CP live-larvae group (Rossi et al., 2026).

Behaviour

The increase in ADFI with dried full-fat MWLM was attributed to the flavour and palatability of mealworm larvae, which may have stimulated feed intake in weaned pigs (Jin et al., 2016).

Live mealworm larvae were rapidly accepted after weaning. Consumption time decreased steadily after day 8 and, during days 29-42, both live-larvae groups generally consumed the supplement within 2 min per pen. Soybean meal offered as the control protein supplement elicited lower feeding interest, frequently reaching the 10-min cut-off or remaining partly refused until the following day; live larvae therefore acted as both a nutrient source and an edible enrichment that stimulated feeding motivation (Rossi et al., 2026).

Poultry

Broilers

Mealworm products are usable in broiler diets, but they are not interchangeable feed ingredients. Responses depend on whether the product is full-fat meal, low-fat meal, fresh or whole larvae, on the inclusion rate, and on diet formulation. The most consistent results are obtained with low or moderate inclusion of full-fat mealworm larvae meal (MWLM), generally around 2.5-7.5%, or with very low additive use around 0.2-0.3%. Higher inclusion, full replacement of soybean meal, or some low-fat products can reduce intake, growth or carcass yield. Mealworm meal should therefore be formulated on digestible amino acids, energy, fat content and calcium-to-phosphorus balance, not treated as a simple soybean meal substitute.

For full-fat MWLM, 2.5-7.5% is a conservative practical range in balanced broiler diets, with 5% often giving the best compromise between performance, gut response and product quality. Inclusion around 10% can work, especially with whole dried larvae, but results are product- and formulation-dependent. Inclusion of 15%, total soybean meal replacement, or high inclusion of low-fat meal is riskier. Very low inclusion of full-fat MWLM or Zophobas morio larvae meals at 0.2-0.3% may be considered for functional effects on intake, microbiota or immune traits, but these levels do not replace a protein source. Diets should be formulated on digestible amino acids and metabolisable energy, with attention to fat content, chitin, calcium and phosphorus balance, and the differences between full-fat, defatted, fresh and whole-larvae products.

Nutritional value

Full-fat MWLM is rich in protein, fat and energy. In broilers, total tract apparent digestibility coefficients were 60% for DM, 66% for organic matter, 60% for crude protein, 88% for ether extract and 64% for gross energy; AMEn was 16.02 MJ/kg DM, and average apparent ileal amino acid digestibility was 86% (De Marco et al., 2015).

Performance

MWLM included at 5 or 10% in a 19% crude protein sorghum-soybean meal starter diet from 7 to 21 days of age did not significantly affect feed intake, weight gain or feed efficiency (Ramos-Elorduy et al., 2002). Full replacement of soybean meal by 29.65% full-fat MWLM from 30 to 62 days did not modify final live weight, body-weight gain or intake in male Shaver brown broilers, but improved feed conversion ratio (FCR) despite lower apparent ileal digestibility of dry matter, organic matter and crude protein (Bovera et al., 2016). In medium-growing free-range female chickens, 7.5% full-fat MWLM replacing corn gluten meal from 43 to 97 days did not affect growth, FCR, mortality or slaughter weight (Biasato et al., 2016).

In Ross 708 broilers, full-fat MWLM at 5, 10 and 15% generally stimulated early body weight and feed intake, but the response was not linear at slaughter. In females, 5% gave the highest final live weight and carcass weight, while 15% tended to worsen FCR. In males, final live weight was highest at 5%, whereas 15% impaired overall FCR and intestinal morphology (Biasato et al., 2017; Biasato et al., 2018). MWLM at 2, 4 and 8% improved starter body weight and average daily gain in Ross 308 broilers, with an estimated optimum close to 4%; fresh mealworm corresponding to 4% dried meal performed less well than dried meal in the starter phase (Elahi et al., 2020). MWLM at 2.5% improved starter body-weight gain and FCR, while 5% gave no additional advantage (Sedgh-Gooya et al., 2022).

Very low inclusions can act as functional additives rather than major protein sources. MWLM at 0.2% increased feed intake during 15-35 days and over the whole 1-35 day period in one experiment, while 0.2-0.3% full-fat MWLM or Zophobas morio meals increased body-weight gain and feed intake without a clear FCR penalty when added on top of complete diets (Jozefiak et al., 2018; Benzertiha et al., 2019). Total replacement of soybean meal by MWLM in slow-growing chickens reduced weight gain and intake, although final live weight and FCR were not significantly different, suggesting that total replacement is less secure than partial replacement (Nieto et al., 2022). Full-fat MWLM at 10% improved final body weight and average daily gain compared with the control, whereas low-fat MWLM from 7.5 to 10% reduced body-weight gain and worsened FCR. Full-fat MWLM at 2 or 4% did not impair performance in a large semi-commercial trial (Vasilopoulos et al., 2023; Petkov et al., 2024; Tóth et al., 2026).

Product quality

Carcass and meat responses were mostly neutral at moderate inclusion. Full replacement of soybean meal by full-fat MWLM did not alter most carcass traits or the chemical composition of breast meat, although digestive tract and spleen weights increased and breast pH and cooking losses were higher (Bovera et al., 2016). In free-range chickens, 7.5% full-fat MWLM did not affect carcass, breast or thigh weights, abdominal fat, meat pH, colour, drip loss or proximate composition. Breast meat had higher oleic and alpha-linolenic acids and lower atherogenicity and thrombogenicity indexes (Biasato et al., 2016; Dabbou et al., 2019).

In female broilers, carcass weight and abdominal fat increased with full-fat MWLM , whereas male broilers showed no significant carcass response (Biasato et al., 2017; Biasato et al., 2018). Dried mealworm meal at 2-8% did not significantly affect carcass composition or meat quality, while fresh mealworm reduced abdominal fat relative to the comparable dried treatment (Elahi et al., 2020). Full-fat MWLM at 10% increased carcass yield and improved several meat composition and colour traits, with lower saturated fatty acids and a higher polyunsaturated-to-saturated fatty acid ratio (Vasilopoulos et al., 2023).

Low-fat MWLM was less favourable when used at high doses: 7.5 and 10% reduced carcass weight and breast yield, and 10% increased the proportion of back (Petkov et al., 2024). However, full-fat MWLM at 2 or 4% increased breast yield from 27.6% in controls to 29.2-29.4% without reducing carcass or leg yield (Tóth et al., 2026). Higher low-fat MWLM reduced breast pH and primary lipid oxidation during late storage, but promoted lipid hydrolysis and secondary oxidation in thigh meat during earlier storage periods (Vlahova-Vangelova et al., 2026).

Health and physiology

Moderate full-fat MWLM generally did not cause major adverse blood or tissue responses. Free-range chickens fed 7.5% full-fat MWLM showed no significant change in haematological traits, serum biochemistry, heterophil-to-lymphocyte ratio, welfare indicators, intestinal morphometry or histology (Biasato et al., 2016). Female broilers fed 5-15% full-fat MWLM had limited blood changes and no significant alteration of gut morphology or histopathology, whereas male broilers showed normal blood traits but impaired villus height, crypt depth and villus-height-to-crypt-depth ratio at 15% (Biasato et al., 2017; Biasato et al., 2018).

The gut response appears dose-sensitive. In female broilers, 10 and 15% MWLM shifted caecal microbiota and reduced Firmicutes-related indicators compared with 5%, while mucin staining was more favourable at 5% than at 10-15% (Biasato et al., 2019). Small additions of full-fat insect meals also modified gut microbiota: 0.2% MWLM increased ileal Lactobacillus spp./Enterococcus spp. counts and tended to increase Clostridium coccoides/Eubacterium rectale counts, while full-fat MWLM and Zophobas morio meals at 0.2-0.3% reduced some immunoglobulin concentrations and modified immune organ traits (Jozefiak et al., 2018; Benzertiha et al., 2019). MWLM meal at 2-8% caused only small blood changes within physiological ranges, and 2.5-5% MWLM did not impair villus height, crypt depth or their ratio in the jejunum and ileum (Elahi et al., 2020; Sedgh-Gooya et al., 2022).

Full-fat MWLM at 2 and 4% increased serum total protein, total cholesterol and high-density lipoprotein (HDL) cholesterol, without increasing low-density lipoprotein (LDL) cholesterol; ileal length was shorter in MWLM -fed birds, with no evidence of impaired growth or health (Tóth et al., 2026). Mealworms are naturally low in calcium relative to phosphorus. Holding mealworms on calcium-fortified substrates increased their calcium content, and calcium in fortified mealworms was 76% as bioavailable as calcium from oyster shell for bone ash in growing chicks (Klasing et al., 2000).

Behaviour and acceptability

Broilers can develop a preference for MWLM . In a cafeteria-type study, birds offered separate feeders containing maize grain, extruded semi-whole soybean, a supplement mix and MWLM gradually consumed up to half of total intake as MWLM. Overall intake and growth were lower than in birds receiving a complete control diet, because the free-choice diet was not nutritionally balanced, but FCR improved late in the trial (Nascimento Filho et al., 2020). Whole MWLM did not impair measured welfare traits: diarrhoea, feather score, litter score, wooden breast and white striping were not adversely affected, and some welfare indicators improved (Vasilopoulos et al., 2023).

Environmental aspects

A life-cycle assessment of Austrian organic mealworm production estimated 20.4 kg CO2-equivalent, 213.66 MJ non-renewable energy, 22.38 m2 agricultural land occupation, 159.52 g SO2-equivalent terrestrial acidification and 12.41 g P-equivalent freshwater eutrophication per kg edible mealworm protein. Feed supply and heating were the main hotspots. Compared with a selected Austrian organic broiler system, mealworm protein had lower impacts for greenhouse gas emissions, energy use, land occupation and acidification, but slightly higher freshwater eutrophication (Dreyer et al., 2021).

Laying hens

In laying hens, evidence is limited. MWLM may replace fish flour, while 10% MWLM appears useful in peak-laying hens for stronger eggshells and firmer meat. Early work reported that Tenebrio molitor and Tenebrio mauritanicus were the most suitable worm species tested for laying hens. Drying larvae at 100°C for 200 min reduced degraded protein and amino acids, and the dried larvae flour was considered an adequate fish-flour substitute. The egg-laying ratio was 7.0-12.0% higher than with trace element additives and 2.4% higher than with a good-quality feed (Giannone, 2003; Wang et al., 1996).

In Hy-Line Brown hens fed 0, 5, 10 or 20% MWLM for 35 days, responses were age-dependent. In 96-day-old pre-laying hens, most traits were little affected, and 20% MWLM reduced glutamate and total amino acids in breast muscle. In 236-day-old peak-laying hens, 10% MWLM improved meat texture and eggshell strength, while 10 and 20% MWLM increased total amino acids. However, 10 and 20% TM reduced breast meat pH, and 5% MWLM reduced antioxidant status. The proposed strategy was less than 5% MWLM for pre-laying hens and 10% for peak-laying hens (Lan et al., 2025).

Quails

Mealworm products can be used in quails, but only at controlled levels. Defatted MWLM was useful in growing quails when it replaced a moderate share of fish meal, whereas laying quails tolerated only low inclusion. Live larvae were mainly a nutritional and foraging enrichment. In growing Japanese quails, defatted MWLM (76.2% crude protein, 6.6% crude fat, 4.2% chitin and 14.7 MJ/kg metabolisable energy) could replace 25-50% of fish meal without loss of performance; 25% replacement gave the best gain and feed conversion ratio (FCR). Replacing 75-100% reduced growth, feed intake and carcass yield, and increased small intestine and abdominal fat weights (Sarica et al., 2020).

In laying Japanese quails, defatted MWLM at 1.4-5.6% of diet reduced laying rate, egg mass and apparent ileal digestibility of dry matter, organic matter and crude protein, while increasing egg weight and FCR. The lowest inclusion was most suitable (Secci et al., 2021). Live larvae at 10% of expected daily feed intake stimulated feed intake but did not improve egg output or most egg quality traits (Dalle Zotte et al., 2024).

Rabbits

Mealworm frass can be used at 1-3% of growing rabbit diets without impairing growth or main carcass traits, but it modifies meat quality and fatty acid profile. In Gabali rabbits, mealworm frass (19.7% crude protein, 15.3% crude fibre and about 10.2 MJ/kg digestible energy) partly replaced wheat bran and soybean meal for 11 weeks. Slaughter weight, total gain, average daily gain, hot carcass weight, dressing percentage and main carcass cuts were unchanged. Boneless meat percentage was highest at 3% frass. Frass reduced meat moisture, increased fat, lowered shear force at 2-3%, and increased redness and chroma. Meat from rabbits fed 2-3% frass had more saturated fatty acids, while all frass-fed groups had more monounsaturated fatty acids and fewer polyunsaturated fatty acids. Globulin and glucose were lowest at 3%, and alanine aminotransferase was lower at 2-3%. Frass should not be formulated as if it were larvae meal (Radwan et al., 2023).

Fish

Yellow mealworm larvae meal (MWLM) can replace part of fishmeal (FM) in aquafeeds, but the response depends strongly on fish species, fish size, product type and inclusion level. Moderate inclusion generally maintained or improved growth, feed utilisation and some immune or antioxidant indicators, whereas excessive use of full-fat MWLM often reduced growth or diluted omega-3 long-chain polyunsaturated fatty acids in tissues. Defatted MWLM was more suitable than full-fat meal for high fishmeal replacement in European seabass and red seabream. The mealworm lipid fraction is less suitable where preservation of n-3 fatty acids is a priority. Overall, mealworm products are promising protein ingredients, but they should be used with balanced amino acid and lipid formulation, and with attention to chitin, digestibility and product quality.

Nile tilapia (Oreochromis niloticus)

Performance

In Nile tilapia juveniles, MWLM replacing FM protein improved growth and feed efficiency up to 45% replacement, but performance declined at 60-75% replacement (Abd El-Naby et al., 2026). A separate trial found the best response at 25% FM replacement by MWLM, with a specific growth rate (SGR) of 3.12%/day, feed utilisation efficiency of 72.0% and protein efficiency ratio of 2.35 (Herawati et al., 2026). In contrast, high full-fat MWLM inclusion at 21-43% of the diet reduced growth and nutrient utilisation despite unchanged feed intake and in vitro protein digestibility (Sánchez-Muros et al., 2015). In FM-free diets, 10% full-fat MWLM was less effective than the corresponding fishmeal diet, but Saccharomyces cerevisiae supplementation improved its use (Anany et al., 2025).

Product quality

Whole-body composition was little affected when dried MWLM replaced FM protein up to 75% (Abd El-Naby et al., 2026). Flesh nutritional quality was highest at 50% fishmeal replacement in one trial, where essential amino acids and eicosapentaenoic acid plus docosahexaenoic acid (EPA + DHA) were highest (Herawati et al., 2026).

Health and physiology

The best physiological response generally occurred at moderate inclusion. At 45% FM-protein replacement, Nile tilapia showed increased digestive enzyme activities, improved intestinal morphology, higher antioxidant and immune responses, and no evident liver inflammation; higher levels caused hepatic vacuolation (Abd El-Naby et al., 2026). The combination of MWLM and S. cerevisiae improved intestinal villus structure, liver histology, blood indicators, lysozyme activity, phagocytic response and antioxidant status (Anany et al., 2025).

Seabreams: gilthead seabream (Sparus aurata) and red seabream (Pagrus major)

Performance

In gilthead seabream, 25% full-fat MWLM, equivalent to 35% FM replacement on a protein basis, improved final weight, weight gain, SGR and feed conversion ratio (FCR), whereas 50% inclusion reduced crude protein and ether extract digestibility and penalised dressed yield (Piccolo et al., 2017). In red seabream, defatted MWLM fully replacing FM produced higher body-weight gain, SGR and feed intake than the FM control, while adding mealworm oil to the same diet reduced performance (Ido et al., 2019).

Product quality

In gilthead seabream, fillet yield and skin colour were not affected by MWLM, but dressed yield decreased as inclusion increased and viscerosomatic index was highest at 50% inclusion (Piccolo et al., 2017). In red seabream, mealworm oil was a limiting component because mealworm larvae contained little omega-3 fatty acid compared with fish oil (Ido et al., 2019).

Health and physiology

Red seabream fed 5-10% defatted MWLM before challenge with Edwardsiella tarda had higher post-challenge survival, indicating a functional health effect (Ido et al., 2019). In gilthead seabream fed 25% MWLM, hepatic protein changes were less marked than in European seabass or rainbow trout exposed to higher inclusion levels, although both apoptosis and autophagy indicators were activated (Mente et al., 2022).

European seabass (Dicentrarchus labrax)

Performance and digestibility

European seabass tolerated 25% full-fat MWLM without a clear performance penalty, but 50% inclusion reduced final body weight, weight gain, SGR and feeding rate. The diet containing 25% full-fat MWLM had higher dry matter and crude protein apparent digestibility coefficient (ADC) than the FM control, with crude protein ADC of 92.3% compared with 90.0% (Gasco et al., 2016). Ingredient testing showed that full-fat and defatted MWLMs had the best nutritional value among the insect meals tested for this species, with crude protein ADC of 89.2 and 93.0%, respectively (Basto et al., 2020). Defatted MWLM replaced 40-80% of fishmeal without altering feed intake or weight gain over 10 weeks, and 50% replacement caused no adverse metabolic effect over 16 weeks; total FM replacement induced hepatic metabolic changes that may compromise long-term health (Basto et al., 2021; Basto et al., 2023).

Product quality

Full-fat MWLM changed whole-body fatty acids more than proximate composition. Oleic and linoleic acids increased, while EPA, DHA and the n-3/n-6 ratio decreased, especially at 50% inclusion (Gasco et al., 2016). Defatted MWLM is therefore preferable when high FM replacement is required without excessive dilution of marine fatty acids.

Health and physiology

A 24.75% full-fat MWLM diet decreased serum ceruloplasmin, myeloperoxidase and nitric oxide, indicating an anti-inflammatory response, and increased serum anti-protease activity, while exogenous proteases reduced some serum antibacterial responses (Henry et al., 2018). At liver level, 50% full-fat MWLM altered 81 protein spots and induced autophagy with reduced Bax expression and Bax/B-cell lymphoma 2 ratio (Mente et al., 2022).

Behaviour and food intake

Defatted MWLM did not affect central homeostatic regulation of food intake. Replacement of 40 or 80% of FM did not change the expression of the main orexigenic or anorexigenic neuropeptides in the hypothalamus or telencephalon (Basto et al., 2021).

Salmonids: rainbow trout (Oncorhynchus mykiss)

Performance

In rainbow trout fry, full-fat MWLM improved weight gain and SGR up to 14% inclusion; FCR was lower and protein efficiency ratio higher in mealworm-fed fish than in the control (Jeong et al., 2020). In larger rainbow trout, an 18% full-fat MWLM diet replacing 50% of FM gave higher final weight and better protein utilisation than a black soldier fly diet and was at least comparable with the control (Melenchón et al., 2022). A high 60% mealworm diet reduced individual weight gain and feeding rate in a proteome study (Mente et al., 2022).

Product quality

In fry, whole-body and muscle proximate composition, muscle essential amino acids and plasma biochemical indicators were not significantly changed (Jeong et al., 2020). In larger trout, the 18% MWLM diet altered fillet composition by lowering moisture and raising protein, and reduced protein digestibility compared with the control (Melenchón et al., 2022).

Health and physiology

MWLM stimulated innate responses in rainbow trout fry, with higher myeloperoxidase activity at 7% inclusion and higher lysozyme activity at 14 and 28% inclusion (Jeong et al., 2020). In larger trout, the MWLM diet increased intestinal alkaline protease and amylase activities and liver antioxidant activity, while most immune indicators were unchanged (Melenchón et al., 2022). At 60% inclusion, hepatic protein abundance was strongly modified and apoptosis was suppressed through autophagy (Mente et al., 2022).

African catfish (Clarias gariepinus)

In African catfish fingerlings, sun-dried MWLM replaced up to 40% of FM without reducing growth or feed utilisation, and fish still grew well at 80% replacement. Complete FM replacement gave the lowest performance. Live mealworms alone depressed growth slightly, but mealworms combined with commercial catfish pellets supported growth equal to, or better than, pellets alone. Mealworm-fed African catfish tended to have higher carcass lipid, reflecting the high lipid content of mealworms and mealworm meal (Ng et al., 2001).

Mandarin fish (Siniperca scherzeri)

In juvenile mandarin fish, full-fat MWLM at 10-20% of the diet improved weight gain, SGR, feed efficiency and protein efficiency ratio, with the best response at 20% inclusion. At 30% inclusion, performance declined slightly but remained numerically better than the control. Whole-body composition, fillet proximate composition and fillet amino acid composition were not markedly altered. However, fillets from MWLM-fed fish contained more saturated and monounsaturated fatty acids and less n-3 polyunsaturated fatty acids than control fillets. Mealworm inclusion reduced plasma cholesterol at the highest level and increased serum lysozyme and glutathione peroxidase activities, indicating immune and antioxidant stimulation (Sankian et al., 2018).

Senegalese sole (Solea senegalensis)

In Senegalese sole, full-fat MWLM included at 5-15% caused no mortality and did not reduce final body weight. Growth rate and feed efficiency improved gradually with mealworm inclusion, and SGR was highest when 15% mealworm meal replaced mainly plant ingredients. Muscle protein was unaffected, while muscle total lipid and neutral lipid contents decreased in fish fed the 10% MWLM diet replacing marine ingredients and the 10-15% MWLM diets replacing plant ingredients. Despite the fatty acid profile of full-fat MWLM, muscle DHA and total n-3 polyunsaturated fatty acids were maintained (Hachero-Cruzado et al., 2024).

Crustaceans

Yellow mealworm products can replace part of fishmeal (FM) in crustacean feeds, with strongest evidence in Pacific white shrimp. Moderate replacement generally maintained or improved growth, feed efficiency and innate immunity, most consistently around 30-50% FM replacement (Motte et al., 2019; Sharifinia et al., 2023; Shin et al., 2021). The main limitation is not crude protein but lipid quality and inclusion level. Mealworm larvae meal (MWLM) is digestible for shrimp, especially for lipid and energy, but it contains little or no eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), so high inclusion can reduce long-chain n-3 polyunsaturated fatty acids in edible tissues. In narrow-clawed crayfish, 50% FM replacement improved growth and moulting, but survival decreased, probably because frequent moulting increased vulnerability to cannibalism (Panini et al., 2017; Mazlum et al., 2021).

Pacific white shrimp (Litopenaeus vannamei)

Digestibility and nutritional value

In Pacific white shrimp, MWLM had apparent digestibility coefficients (ADC) of 84.2% for protein, 97.5% for lipid, 90.1% for energy and 80.8% for dry matter; chitin digestibility was lower at 28.0%. Amino acid availability was high for methionine, arginine, lysine and taurine. The tested MWLM contained 47.5% crude protein, 30.8% lipid and 3.24% chitin on a dry matter basis, but lacked EPA and DHA (Shin et al., 2021).

Performance

Defatted MWLM replacing 25-100% of FM in isoproteic and isoenergetic diets improved growth and feed conversion ratio (FCR), with the best response at 50% replacement. Weight gain reached 5.27 g/shrimp compared with 3.94 g/shrimp in the control, and FCR improved from 1.59 to 1.20, without reducing feed intake or survival (Motte et al., 2019). Another trial found that body weight gain, feed efficiency and hepatopancreas index increased up to 30% FM replacement and then declined, while survival was not significantly affected (Sharifinia et al., 2023). In a comparative insect-meal trial, replacing 10% tuna by-product meal with MW did not significantly affect growth, FCR, protein efficiency ratio (PER) or survival (Shin et al., 2021).

Product quality

Replacing FM with full-fat MWLM did not change shrimp muscle moisture, protein or ash, but muscle lipid increased linearly. The fatty acid profile reflected the diet: oleic acid increased, whereas EPA, DHA and total n-3 polyunsaturated fatty acids decreased. The n-3/n-6 ratio remained between 0.50 and 0.67 (Panini et al., 2017). Colour and firmness of raw and cooked shrimp were not affected by MW. In the comparative trial, whole-body proximate composition was unchanged, but EPA and DHA in muscle were lower in shrimp fed insect-meal diets than in the control (Panini et al., 2017; Shin et al., 2021).

Health and physiology

Defatted MWLM improved resistance to Vibrio parahaemolyticus. Mortality was 76.9% lower at 50% FM replacement than in the control, and bacterial persistence in haemolymph decreased as MWLM inclusion increased. Phenoloxidase (PO), total haemocyte count (THC) and haemolymph protein increased before challenge, while PO and THC remained higher after challenge (Motte et al., 2019). In the 60-day trial, haemolymph cholesterol, triglycerides and glucose decreased as MWLM replacement increased. Superoxide dismutase (SOD), alkaline phosphatase and acid phosphatase peaked at 30% replacement, PO was higher from 15 to 60%, and lysozyme activity was highest at 60%. Dietary MW also increased PO, glutathione peroxidase and nitro-blue tetrazolium activity in the comparative trial (Sharifinia et al., 2023; Shin et al., 2021).

Narrow-clawed crayfish (Pontastacus leptodactylus)

In juvenile narrow-clawed crayfish, full-fat MWLM replacing 50% of FM improved final weight, weight gain, specific growth rate (SGR), PER, apparent net protein utilisation and moulting frequency compared with both the control and the 100% replacement diet. Final weight reached 0.85 g with 50% replacement, compared with 0.28 g in the control and 0.27 g with complete replacement. The best FCR was obtained with 50% replacement, at 1.22 compared with 3.73 in the control and 5.31 with 100% replacement, though FCR differences were not significant. Moulting frequency was highest with 50% replacement (71.4%), but survival was lower (46.7%) than in the control and 100% replacement groups (53.3%). Whole-body composition was affected by diet. Crayfish fed the 50% replacement diet had the highest lipid content and crude protein similar to the control, whereas the 100% replacement diet resulted in lower crude protein and higher moisture. Overall, 50% FM replacement by full-fat MW improved juvenile crayfish growth and moulting, but complete replacement was not advisable under the tested conditions (Mazlum et al., 2021).

Nutritional tables

Tables of chemical composition and nutritional value

Avg: average or predicted value; SD: standard deviation; Min: minimum value; Max: maximum value; Nb: number of values (samples) used