Introduction
The global demand for animal protein continues to rise sharply in line with population growth and changing dietary habits and is projected to increase by approximately 75% by 2050 (Van Huis and Oonincx, Reference Van Huis and Oonincx2017). Poultry meat is expected to represent more than half of the global meat supply, reaching nearly 152 million t by 2030 (OCDE-FAO, 2021). This trend will place additional pressure on feed ingredient availability, particularly protein sources. Currently, soybean meal and fish meal remain the predominant protein inputs in poultry diets (Elahi et al., Reference Elahi, Wang, Ma, Wu, Qi and Zhang2020), yet both are increasingly challenged by environmental concerns, market price volatility, and supply chain instability (Moreno et al., Reference Moreno, Ton, Rosa and de Freitas2021). These limitations underscore the urgent need for alternative, sustainable protein ingredients.
Edible insects have emerged as promising candidates in this context. Insect meals typically contain 47%–60% crude protein, a balanced essential amino acid profile, and significant levels of vitamins and minerals (Rumpold and Schlüteret, Reference Rumpold and Schlüter2013). They can also be produced with a lower environmental footprint compared with conventional livestock, generating fewer greenhouse-gas emissions and requiring less land and water (Hong, Han, and Kim, Reference Hong, Han and Kim2020). Despite these advantages, insect-based feeds still face practical barriers, including variability in nutrient composition among batches, the presence of antinutritional factors such as chitin, and relatively high processing costs (Sogari et al., Reference Sogari, Amato, Biasato, Chiesa and Gasco2019; Gasco et al., Reference Gasco, Acuti, Bani, Dalle Zotte, Danieli, De Angelis, Fortina, Marino, Parisi, Piccolo, Pinotti, Prandini, Schiavone, Terova, Tulli and Roncarati2020). Although insect-derived proteins have gained increasing attention as sustainable feed ingredients, their regulatory adoption remains uneven across regions. In Peru, no specific legislation currently governs the use of insect meals in poultry feed, whereas the European Union has established a regulatory framework authorizing the use of processed animal proteins derived from several insect species, including Tenebrio molitor, in poultry nutrition (Gasco et al., Reference Gasco, Acuti, Bani, Dalle Zotte, Danieli, De Angelis, Fortina, Marino, Parisi, Piccolo, Pinotti, Prandini, Schiavone, Terova, Tulli and Roncarati2020; European Commission, 2021). This regulatory disparity highlights the need for scientific evidence to support future policy development and the adoption of insect-based feed ingredients in Latin America.
Within this group, T. molitor larvae meal (TMM) has attracted particular attention. On a dry matter basis, it contains 47%–60% crude protein, 19%–50% lipids, and 2%–7% minerals (Hong et al., Reference Hong, Han and Kim2020; Machona et al., Reference Machona, Matongorere, Chidzwondo and Mangoyi2022), in addition to bioactive compounds with potential functional properties. Several studies have demonstrated that partial substitution of soybean meal with TMM in broiler diets can maintain growth performance and, in some cases, improve carcass yield and meat physicochemical traits (Hamani et al., Reference Hamani, Taffa, Issa, Mahamadou, Detilleux and Moula2022; Mlaga et al., Reference Mlaga, Agboka, Attivi, Tona and Osseyi2022; Vasilopoulos et al., Reference Vasilopoulos, Giannenas, Savvidou, Bonos, Rumbos, Papadopoulos, Fortomaris and Athanassiou2023). However, relevant knowledge gaps remain. In particular, the influence of TMM on sensory quality attributes (e.g., tenderness, flavor, overall acceptability) has been insufficiently explored, especially at intermediate to high inclusion levels (5%–8%). Moreover, most research has focused on the starter or grower phases, whereas the finisher phase is critical for determining carcass composition and final meat quality outcomes.
An additional factor that has received little attention is the role of tropical production environments. High temperatures and humidity impose a constant challenge to poultry systems, where heat stress reduces feed intake and alters the metabolic efficiency of nutrient utilization (Sesay, Reference Sesay2022). In such conditions, dietary adjustments are often required to compensate for reduced intake and ensure optimal growth. Previous studies in tropical regions have shown that diets rich in high-quality, highly digestible protein—particularly of animal origin—can help sustain growth performance and carcass quality even under climatic stress (Beski, Swick, and Iji, Reference Beski, Swick and Iji2015; Iqbal, Reference Iqbal, Manickavasagan, Lim and Ali2022). Evaluating alternative protein sources such as TMM under tropical conditions is therefore highly relevant, since results generated in temperate systems cannot always be extrapolated to hot and humid environments.
Therefore, this study aimed to evaluate the partial replacement of soybean meal with graded levels of TMM in finisher diets for broiler chickens reared under tropical conditions. Specifically, the effects on growth performance, physicochemical characteristics, and sensory quality of breast meat were assessed to provide further evidence regarding the potential of TMM as a sustainable alternative protein source for poultry nutrition.
Materials and methods
All procedures were approved by the Institutional Committee for Ethics in Research with Animals and Biodiversity, Scientific University of the South (Certificate No. 066-CIEI-AB-CIENTÍFICA-2023). The study comprised two sequential phases: first, an evaluation of broiler growth performance in finishing diets containing graded levels of T. molitor larvae meal; and second, a sensory and physicochemical analysis of the resulting breast meat
Evaluation of broiler productive performance
The trial was carried out in Tabalosos (Lamas Province, San Martín, Peru; 525 m a.s.l.; 6°23′18″ S, 76°38′04″ W), a tropical environment with a mean temperature of 25 C and a mean relative humidity of 77%.
T. molitor larvae meal production
Mature T. molitor larvae (≥1.5 cm) were cultured in plastic trays (45 × 30 × 20 cm) on a 10 cm substrate of wheat bran and fruit–vegetable waste, replenished biweekly. After harvest, larvae were frozen at −15 C for 48 h (Larouche et al., Reference Larouche, Deschamps, Saucier, Lebeuf, Doyen and Vandenberg2019), thawed at ambient temperature, blanched in a 90 C water bath for 10 min (Campbell et al., Reference Campbell, Ortuño, Stratakos, Linton, Corcionivoschi, Elliott, Koidis and Theodoridou2020), oven-dried at 60°C to 95% dry matter, and milled at 250 g/min. The proximate composition of the larvae was determined according to AOAC International official methods as follows: moisture (Method 934.01), crude protein by the Kjeldahl method (Method 984.13), crude fat by Soxhlet extraction (Method 920.39), crude fiber (Method 978.10), and crude ash (Method 942.05) (AOAC, 2005). Proximate composition is presented in Table 1.
Proximate composition (% fresh matter) of mature Tenebrio molitor larvae
Table 1. Long description
The table consists of two columns: Component and Percentage. The data rows are as follows:
* Moisture: 60.40
* Crude protein: 21.60
* Crude fat: 11.94
* Crude fiber: 2.97
* Crude ash: 1.53
* Nitrogen free extract: 1.56
Diets, experimental design, and data collection
Three-phase diets: starter (1–10 days), grower (11–21 days), and finisher (22–42 days) were formulated using NRC (1994) as a general reference framework, with final dietary formulations adjusted to meet the nutrient requirements of Cobb 500 broilers according to the Cobb 500 Performance and Nutrition Supplement (2022). Solvent-extracted soybean meal served as the primary protein source during the starter and grower phases. During the finisher phase, the diets contained both solvent-extracted soybean meal (47% crude protein) and extruded full-fat soybeans, the latter providing an additional source of protein and energy. TMM replaced solvent-extracted soybean meal at inclusion levels of 0% (T0, control), 2% (T1), 5% (T2), or 8% (T3). Ingredient composition and calculated nutrient profiles are presented in Table 2.
Ingredient composition and calculated nutrient profile (% as fed) of experimental finishing diets fed to broiler chickens from day 22 to 42
Table 2. Long description
The table is organized into five columns: Ingredient or Nutrient, and four treatment groups: T 0, T 1, T 2, and T 3.
Ingredient Composition (percent as fed):
* Maize (yellow): 60 for all treatments.
* Solvent-extracted soybean meal (47 percent C P): Decreases from 21 in T 0 to 18.9 in T 1, 16 in T 2, and 13 in T 3.
* Tenebrio molitor larvae meal: Increases from 0 in T 0 to 2.1 in T 1, 5 in T 2, and 8 in T 3.
* Extruded full-fat soybeans: 9.2 for all treatments.
* Soybean oil: 5 for all treatments.
* Calcium carbonate: 1 for all treatments.
* Salt: 0.4 for all treatments.
* Dicalcium phosphate: 1.8 for all treatments.
* Mycotoxin adsorbent: 0.3 for all treatments.
* Sodium bicarbonate: 0.1 for all treatments.
* D L - Methionine: 0.25 for all treatments.
* L - Threonine: 0.1 for all treatments.
* Choline chloride: 0.15 for all treatments.
* Premix: 0.1 for all treatments.
* Fungicide: 0.1 for all treatments.
* Betaine: 0.1 for all treatments.
* Acidifier: 0.1 for all treatments.
* Antioxidant: 0.05 for all treatments.
* Coccidiostat: 0.05 for all treatments.
* L - Lysine: 0.15 for all treatments.
* Pigment: 0.05 for all treatments.
Calculated Nutrient Profile:
* Dry matter (percent): Increases from 88.21 in T 0 to 89.09 in T 3.
* A M E n (kcal/kg): Decreases from 3184.47 in T 0 to 3004.47 in T 3.
* Crude protein (percent): Increases from 18.22 in T 0 to 18.97 in T 3.
* Ether extract (percent): Increases from 9.1 in T 0 to 11.43 in T 3.
* Calcium (percent): Decreases from 0.91 in T 0 to 0.88 in T 3.
* Available phosphorus (percent): Decreases from 0.44 in T 0 to 0.42 in T 3.
* Sodium (percent): 0.20 in T 0 and 0.19 in T 1 through T 3.
* Total lysine (percent): Decreases from 1.07 in T 0 to 0.84 in T 3.
* Total methionine (percent): Decreases from 0.54 in T 0 to 0.49 in T 3.
* Total threonine (percent): Decreases from 0.79 in T 0 to 0.65 in T 3.
Note: AMEn, apparent metabolizable energy, nitrogen‑corrected.
The experiment was conducted in a poultry house (12 × 4.8 m) with concrete flooring, wooden supports, and a native-leaf roof. Twelve pens (1.5 m2 each), arranged in two rows of six, were equipped with 10 cm of wood-shavings–lime litter, a 100 W heat lamp, a circular feeder, and a 1 L drinker. Environmental temperature and humidity were monitored daily. 180 Cobb 500 broilers (22 days of age) were randomly allocated to four dietary treatments (three replicate pens per treatment; 15 birds per pen). Feed and water were provided ad libitum. Body weight and feed intake were recorded at the onset (day 22) and conclusion (day 42) of the finisher phase; weight gain and feed conversion ratio were subsequently calculated. Mortality was monitored and recorded throughout the experimental period.
Sensory and physicochemical analysis of breast meat
At the conclusion of the finisher phase, eight birds per treatment were randomly selected, fasted for 8 h (Mendes, Reference Mendes2001), humanely stunned by cervical dislocation, prior to slaughter in accordance with the recommendations of the World Organization for Animal Health (WOAH, 2023) and the Peruvian Animal Welfare and Protection Law (Law No. 30407; Congreso de la República del Perú, 2016). Breast muscles were excised, yielding 32 samples: 16 for sensory evaluation, 16 for physicochemical analyses, and four for proximate composition. Each sample was sectioned longitudinally; the right half was subdivided into three equal portions for pH, titratable acidity, and water activity measurements, while the left half was reserved for water-holding capacity assessment. All portions were vacuum-packed and stored at −18 C until analysis.
Sensory analysis
An untrained panel of 92 habitual broiler meat consumers (18–50 years), free from allergies or sensory impairments, was recruited from the Food Technology Laboratory at Universidad Científica del Sur to conduct a consumer acceptance (hedonic) test. Prior to testing, participants were instructed to refrain from smoking, coffee, or high-sugar foods for 8 h and to hydrate with mineral water until thirst was relieved.
Meat samples were thawed at 4 C for 16 h (Zhang et al., Reference Zhang, Huang, Wang, Xing and Xu2020), cut into approximately 2-cm-thick fillets, lightly seasoned with coarse salt, and convectively baked at 180 C to an internal temperature of 72 ± 1 C (Damaziak et al., Reference Damaziak, Stelmasiak, Riedel, Zdanowska-Sąsiadek, Bucław, Gozdowski and Michalczuk2019; Zhang et al., Reference Zhang, Huang, Wang, Xing and Xu2020), a cooking endpoint selected to ensure microbiological safety while minimizing heat-induced changes in sensory attributes. Cooked fillets were cut into 15 ± 5 g portions (Cho and Choi, Reference Cho and Choi2021), coded with three-digit numbers and presented in randomized order. Each panelist evaluated all four dietary treatments during a single session; thus, each treatment received 92 consumer evaluations. Appearance, juiciness, aroma, flavor, tenderness, and texture were rated on a 7-point hedonic scale (1 = dislike extremely, 7 = like extremely) (Cho and Choi, Reference Cho and Choi2021). Given the close relationship between aroma and flavor, a certain degree of perceptual overlap cannot be excluded, and results were interpreted with this limitation in mind. Panelists rinsed with water between samples.
Physicochemical analysis
All measurements were conducted in triplicate. The pH was recorded one week post-slaughter after thawing (4 C/16 h) with a digital potentiometer (Oakton pH50S, Singapore) inserted directly into the geometric center of the sample (Zhang et al., Reference Zhang, Huang, Wang, Xing and Xu2020).
Titratable acidity was measured on 10 g of raw breast meat after thawing at 4°C for 16 h, according to AOAC International official method 16.247 (AOAC, 2005), and expressed as a percentage of lactic acid:
Water activity was measured on 0.4 cm slices using an Aqualab 4TEV DUO (Meter Group, Pullman, WA, USA), calibrated with 0.98 and 1.00 aw standards. Samples were thawed at room temperature for 2 h in their sealed packaging. Thereafter, breasts were sectioned into approximately 0.4 cm-thick slices and immediately placed into the Aqualab sample chamber, where water activity was measured at 25 ± 1 C.
Water-holding capacity was determined by quantifying both thawing and cooking losses, adapting the protocol of Zhang et al. (Reference Zhang, Huang, Wang, Xing and Xu2020). Briefly, each breast sample was weighed, frozen at −18 C, and then thawed at 4 C for 16 h. Post-thaw weight was recorded and thawing loss calculated.
Breast fillets were vacuum-sealed in polyethylene bags and cooked in a water bath at 80 C until the internal temperature reached 75 C, following a standardized endpoint commonly used for cooking-loss and water-holding capacity determinations to ensure measurement consistency among samples (Zhang et al., Reference Zhang, Huang, Wang, Xing and Xu2020). Samples were then cooled in tap water for approximately 20 min. Afterward, samples were removed from the bags, gently blotted dry with filter paper, and reweighed:
Statistical analysis
All statistical analyses were conducted at α = 0.05. Broiler growth performance variables (initial body weight, final body weight, body weight gain, feed intake, and feed conversion ratio), as well as physicochemical parameters of breast meat (pH, acidity, water activity, thawing loss, and cooking loss), were analyzed using a one-way analysis of variance (ANOVA) with dietary treatment as a fixed effect (treatment df = 3; error df = 8). Normality of physicochemical variables was assessed using the Kolmogorov–Smirnov test. All analyses were performed using R software (version 4.2.2; R Core Team, 2022). When significant treatment effects were detected, pairwise comparisons of least-squares means were conducted using Tukey’s test.
Sensory evaluation data, obtained from a consumer acceptance (hedonic) test using an untrained panel, were treated as nonparametric variables and analyzed using the Kruskal–Wallis test. When significant differences were observed, multiple comparisons were adjusted using the Holm–Bonferroni correction.
Results
Evaluation of broiler growth performance
No significant differences were observed among treatments for any growth performance parameter (P > 0.44) (Table 3), and no mortality was recorded during the experimental period.
Effect of dietary inclusion level of Tenebrio molitor larvae meal during the finisher phase (22–42 days) on production performance of broiler at day 42 of age
Table 3. Long description
The table consists of six columns: Parameter, T 0, T 1, T 2, T 3, and P-value.
* Initial body weight in grams: T 0 is 965.9 plus or minus 35.6; T 1 is 990.9 plus or minus 19.8; T 2 is 1010.9 plus or minus 10.5; T 3 is 1013.0 plus or minus 21.4; P-value is 0.45.
* Final body weight in grams: T 0 is 2752.1 plus or minus 80.5; T 1 is 2725.2 plus or minus 92.3; T 2 is 2837.4 plus or minus 38.4; T 3 is 2717.8 plus or minus 106.6; P-value is 0.56.
* Body weight gain in grams per bird: T 0 is 1786.2 plus or minus 45.9; T 1 is 1734.3 plus or minus 91.1; T 2 is 1826.4 plus or minus 46.2; T 3 is 1704.8 plus or minus 123.1; P-value is 0.56.
* Body weight gain in grams per day per bird: T 0 is 85.1 plus or minus 2.2; T 1 is 82.5 plus or minus 4.3; T 2 is 86.9 plus or minus 2.2; T 3 is 81.2 plus or minus 5.8; P-value is 0.49.
* Feed intake in grams per bird: T 0 is 3136.8 plus or minus 22.8; T 1 is 3136.7 plus or minus 19.9; T 2 is 3139.0 plus or minus 22.4; T 3 is 3112.4 plus or minus 16.9; P-value is 0.47.
* Feed conversion ratio: T 0 is 1.6 plus or minus 0.03; T 1 is 1.7 plus or minus 0.09; T 2 is 1.63 plus or minus 0.03; T 3 is 1.7 plus or minus 0.12; P-value is 0.52.
Sensory and physicochemical analysis of breast meat
Juiciness, flavor, tenderness, and texture were significantly lower in the 5% inclusion group (T2) compared with the control (T0) and 2% (T1) (P < 0.05), whereas the 8% inclusion group (T3) did not differ significantly from the other treatments (Table 4). Appearance and aroma scores did not vary among treatments (P > 0.10). The pH showed a statistically significant treatment effect according to the ANOVA (P = 0.04). However, Tukey’s multiple-comparison test did not detect significant differences between treatment pairs, which may be attributed to the small sample size (n = 3 per treatment) and the limited magnitude of the observed differences. In contrast, acidity and water activity did not differ among treatments (P > 0.05), and neither thawing nor cooking losses were affected by dietary inclusion level (P > 0.25) (Table 5).
Sensory attributes of broiler breast meat fed finishing diets containing 0, 2, 5, or 8% Tenebrio molitor larvae meal (T0–T3)
Table 4. Long description
The table consists of six columns: Sensory Attribute, T 0, T 1, T 2, T 3, and P-value.
* Appearance: T 0 is 5.15 plus or minus 1.26, T 1 is 5.21 plus or minus 1.37, T 2 is 5.08 plus or minus 1.13, T 3 is 5.47 plus or minus 1.25, P-value is 0.12.
* Juiciness: T 0 is 5.50 plus or minus 1.20 super a, T 1 is 5.57 plus or minus 1.35 super a, T 2 is 4.87 plus or minus 1.42 super a, T 3 is 5.32 plus or minus 1.39 super a, P-value is less than 0.01.
* Aroma: T 0 is 5.26 plus or minus 1.25, T 1 is 5.13 plus or minus 1.28, T 2 is 4.81 plus or minus 1.29, T 3 is 5.14 plus or minus 1.42, P-value is 0.12.
* Flavor: T 0 is 5.58 plus or minus 1.28 super a, T 1 is 5.59 plus or minus 1.37 super a, T 2 is 4.96 plus or minus 1.62 super a, T 3 is 5.44 plus or minus 1.27 super a, P-value is 0.03.
* Tenderness: T 0 is 5.33 plus or minus 1.22 super a, T 1 is 5.52 plus or minus 1.33 super a, T 2 is 4.67 plus or minus 1.42 super a, T 3 is 5.33 plus or minus 1.38 super a, P-value is less than 0.01.
* Texture: T 0 is 5.47 plus or minus 1.11 super a, T 1 is 5.53 plus or minus 1.29 super a, T 2 is 4.91 plus or minus 1.32 super a, T 3 is 5.34 plus or minus 1.48 super a, P-value is 0.01.
Note: Means with different superscripts are significantly different where P is less than 0.05.
a Means with different superscripts are significantly different (P < 0.05).
Physicochemical properties of broiler breast meat fed finishing diets containing 0, 2, 5, or 8% Tenebrio molitor larvae meal (T0–T3)
Table 5. Long description
The table consists of seven columns: Parameter, T 0, T 1, T 2, T 3, S E M, and P-value.
* p H: T 0 is 5.87 plus or minus 0.11, T 1 is 5.71 plus or minus 0.02, T 2 is 5.70 plus or minus 0.16, T 3 is 5.87 plus or minus 0.10, S E M is 0.05, P-value is 0.04.
* Acidity: T 0 is 0.33 plus or minus 0.00, T 1 is 0.38 plus or minus 0.04, T 2 is 0.34 plus or minus 0.03, T 3 is 0.32 plus or minus 0.01, S E M is 0.01, P-value is 0.09.
* Water activity: All treatments T 0 through T 3 are 0.99 plus or minus 0.00, S E M is 0.00, P-value is 1.00.
* percent thawing loss: T 0 is 2.70 plus or minus 0.12, T 1 is 3.02 plus or minus 1.27, T 2 is 4.70 plus or minus 0.65, T 3 is 3.35 plus or minus 1.86, S E M is 0.68, P-value is 0.25.
* percent cooking loss: T 0 is 22.09 plus or minus 3.25, T 1 is 26.43 plus or minus 4.20, T 2 is 24.54 plus or minus 1.11, T 3 is 24.85 plus or minus 3.02, S E M is 1.79, P-value is 0.44.
Note: SEM, standard error of the mean.
Discussion
The present study demonstrated that replacing soybean meal protein with TMM at inclusion levels up to 8% in finishing broiler diets did not compromise growth performance. This finding is consistent with the favorable nutritional composition of TMM, which provides high concentrations of crude protein (~54% dry matter; Hong et al., Reference Hong, Han and Kim2020) and crude fat (~30% dry matter; Hong et al., Reference Hong, Han and Kim2020), an adequate profile of essential amino acids such as methionine (0.78% DM; Nascimento et al., Reference Nascimento, Pereira, Oliveira, Suckeveris, Burin Junior, Soares and Menten2021) and lysine (3.26% DM; Nascimento et al., Reference Nascimento, Pereira, Oliveira, Suckeveris, Burin Junior, Soares and Menten2021), and a high proportion of digestible protein (~95.6%; Hammer et al., Reference Hammer, Moretti, Abbühl-Eng, Kandiah, Hilaj, Portmann and Egger2023). Previous reports have similarly indicated that diets containing TMM support comparable feed intake and growth to soybean meal–based diets (Sedgh-Gooya et al., Reference Sedgh-Gooya, Torki, Darbemamieh, Khamisabadi and Abdolmohamadi2022; Dagnino and Mendoza, Reference Dagnino and Mendoza2024), suggesting that the absence of intake depression in the present trial is likely linked to the good palatability of insect meal. In this context, the comparable feed conversion ratios observed across treatments further indicate that nutrient utilization efficiency was not adversely affected by dietary TMM inclusion, even at the highest level tested. The feed conversion ratio (FCR) values reported in the present study represent the finisher phase (22–42 days of age) rather than the cumulative production period. Feed conversion efficiency is expected to decline with advancing age as a progressively greater proportion of metabolizable energy is allocated to maintenance functions instead of growth. Accordingly, finisher-phase FCR values ranging from 1.6 to 1.7 are within the expected range for broilers reared under comparable nutritional and environmental conditions, including tropical production systems (Rostagno et al., Reference Rostagno, Albino, Hannas, Donzele, Sakomura, Perazzo, Saraiva, Teixeira, Rodrigues, Oliveira, Barreto and Brito2017; Aviagen, 2022). Moreover, because FCR is a major determinant of production costs in broiler systems, maintaining comparable values across treatments suggests the potential for cost-effective use of TMM. This interpretation is consistent with previous reports summarized by Van Huis et al. (Reference Van Huis, Van Itterbeeck, Klunder, Mertens, Halloran, Muir and Vantomme2013), which indicate that insect-based protein sources can sustain growth performance while offering economic advantages over conventional ingredients, depending on local production costs and availability. Taken together, these findings indicate that, under tropical feeding and management conditions, TMM can supply nutrients in sufficient quantity and availability to sustain growth during the finisher phase.
Regarding sensory traits, the inclusion of TMM up to 8% did not affect panel scores for appearance or aroma. This observation is consistent with earlier findings (Elahi et al., Reference Elahi, Wang, Ma, Wu, Qi and Zhang2020), where meat color remained unchanged at similar inclusion levels. The absence of color variation is probably due to the dominant influence of pigments such as lutein, zeaxanthin, and retinol from maize and other dietary ingredients (Secci et al., Reference Secci, Moniello, Gasco, Bovera and Parisi2018; Abraham et al., Reference Abraham, Weimer, Scoles, Vargas, Johnson, Robison, Hoverman, Rocheford, Rocheford, Ortiz and Karcher2021), which may have masked any pigmentation effects of TMM. Similarly, no changes in aroma were detected, corroborating reports that incorporation of insect-based ingredients does not impair meat odor (Cullere et al., Reference Cullere, Schiavone, Dabbou, Gasco and Zotte2019; Šťastník et al., Reference Šťastník, Novotný, Roztočilová, Jůzl, Piechowiczová, Kouřil, Satrapová, Lacina, Kalhotka, Pavlata and Mrkvicová2021).
In contrast, differences were observed in other sensory characteristics. Birds receiving 5% and 8% TMM showed reduced scores for juiciness, flavor, tenderness, and texture compared with 0% and 2%. This pattern suggests that sensory quality was adversely affected once dietary TMM inclusion reached 5%. Although mean sensory scores increased numerically at the 8% inclusion level, this apparent recovery was not statistically significant and therefore should not be interpreted as evidence of a biological improvement. Instead, the results suggest the presence of a threshold effect around 5% dietary TMM inclusion, beyond which further increases in TMM inclusion do not appear to produce proportionally greater sensory deterioration. The mechanisms underlying this threshold effect are likely multifactorial and may involve changes in dietary lipid composition, the gradual accumulation of chitin, and the generation of insect-derived volatile compounds that influence flavor perception.
It should also be noted that the experimental diets were formulated to evaluate the progressive replacement of solvent-extracted soybean meal with TMM rather than to be strictly isonitrogenous or isoenergetic. Consequently, gradual differences in the calculated nutrient composition, including metabolizable energy, crude protein, and total amino acid concentrations, accompanied increasing TMM inclusion. Therefore, although the reduced sensory acceptance is biologically consistent with the nutritional characteristics of TMM, the potential contribution of these concurrent dietary nutrient changes cannot be completely excluded. Potential mechanisms include changes in carcass lipid composition, as higher dietary unsaturated fatty acid content can soften fat and alter mouthfeel (Wood et al., Reference Wood, Enser, Fisher, Nute, Richardson and Sheard1999); differences in dietary amino acid composition affecting muscle protein deposition and water-holding capacity (Fang and Zhu, Reference Fang and Zhu2025); and low-level chitin intake from the insect exoskeleton, which may reduce nitrogen digestibility and muscle development (Marono et al., Reference Marono, Piccolo, Loponte, Di Meo, Attia, Nizza and Bovera2015). While the present study did not directly measure chitin content or fatty acid profiles, there are possible compositional bases for this threshold effect. T. molitor larvae meal contains a relatively high proportion of unsaturated fatty acids, particularly oleic (C18:1n9) and linoleic (C18:2n6) acids, which can represent approximately 77%–79% of total fatty acids depending on diet and processing (Rumpold and Schlüter, Reference Rumpold and Schlüter2013; Van Huis et al., Reference Van Huis, Van Itterbeeck, Klunder, Mertens, Halloran, Muir and Vantomme2013). Such high unsaturated fatty acid content may influence the softness and mouthfeel of fat in the muscle, contributing to perceptible changes in juiciness and texture at higher inclusion levels. Additionally, T. molitor larvae contain chitin as part of their cuticle, typically averaging 4.9%–13% of dry matter (Marono et al., Reference Marono, Piccolo, Loponte, Di Meo, Attia, Nizza and Bovera2015). High dietary levels of chitin from shrimp meal have been associated with reduced digestibility and impaired growth performance in broilers (Khempaka et al., Reference Khempaka, Mochizuki, Koh and Karasawa2006), potentially limiting muscle protein deposition and indirectly affecting tenderness and water-holding capacity.
Together, these compositional factors—high unsaturated lipid content and cumulative chitin load—provide a possible explanation for the decline in sensory attributes at inclusion levels above 5%, suggesting this level as a tentative threshold for maintaining favorable sensory traits in broiler breast meat. Furthermore, insect-derived volatiles, such as nutty or cereal-like notes, have been reported to influence flavor perception (Mishyna, Chen, and Benjamin, Reference Mishyna, Chen and Benjamin2019), which could explain the differences detected in the present study. Nevertheless, despite the decline in sensory scores, all attributes remained within acceptable ranges and were not rejected by the sensory panel.
Physicochemical parameters were largely unaffected. No significant differences were observed in acidity, water activity, thawing loss, or cooking loss, in agreement with previous findings in broilers fed insect-based diets (Secci et al., Reference Secci, Moniello, Gasco, Bovera and Parisi2018; Dabbou et al., Reference Dabbou, Gasco, Lussiana, Brugiapaglia, Biasato, Renna, Cavallarin, Gai and Schiavone2019). The acidity values obtained were comparable to those of conventional broiler meat (Gomez-Portilla, Gomez, and Martínez-Benavides, Reference Gomez-Portilla, Gomez and Martínez-Benavides2016), while water activity remained within the recommended ranges for product safety and shelf-life (SENASA, 2021). Although slight treatment-related differences in pH were recorded, the values remained within the physiological range for chicken meat (5.7–6.1; Qiao et al., Reference Qiao, Fletcher, Smith and Northcutt2001) and below the thresholds associated with PSE or DFD conditions (Lipiński et al., Reference Lipiński, Antoszkiewicz, Kotlarczyk, Mazur-Kusnirek, Kaliniewicz and Makowski2019; Beauclercq et al., Reference Beauclercq, Mignon-Grasteau, Petit, Berger, Lefèvre, Métayer-Coustard, Tesseraud, Emond, Berri and Bihan-Duval2022). Variations in pH may reflect interacting factors such as heat stress, metabolic load from rapid growth, and pre-slaughter handling (Paião et al., Reference Paião, Ferracin, Pedrão, Kato and Shimokomaki2013; Freitas et al., Reference Freitas, Carvalho, Soares, Oliveira, Madruga, Neto, Carvalho, Ida and Shimokomak2017). Importantly, the lack of differences in thawing and cooking losses indicates that the reduced juiciness perceived by panelists may be related to subtle changes in intracellular water distribution, lipid quality, or flavor-active compounds, rather than to actual moisture loss during processing.
Beyond its nutritional value, the partial replacement of soybean meal with TMM may contribute to diversifying protein sources for poultry nutrition and reducing reliance on conventional soybean-derived feed ingredients. Insect-derived proteins have been proposed as alternative feed resources capable of partially replacing conventional protein ingredients, including soybean meal, and supporting the diversification of livestock feeding systems (Van Huis et al., Reference Van Huis, Van Itterbeeck, Klunder, Mertens, Halloran, Muir and Vantomme2013; Makkar et al., Reference Makkar, Tran, Heuzé and Ankers2014). Nevertheless, the overall sustainability of TMM depends on factors such as rearing substrates, production scale, processing requirements, energy inputs, and regional supply chains, none of which were evaluated in the present study.
From a practical perspective, dietary inclusion of TMM up to 8% appears nutritionally feasible for broilers reared under tropical conditions. However, if the preservation of favorable sensory characteristics is a priority, inclusion levels may need to remain below 5%. Alternatively, formulation strategies such as amino acid balancing (Marono et al., Reference Marono, Piccolo, Loponte, Di Meo, Attia, Nizza and Bovera2015), adjustment of dietary lipid sources (Yalçin, Özkan, and Acar, Reference Yalçin, Özkan and Acar2024), or antioxidant supplementation (Carreras Ferrer, Reference Carreras Ferrer2005) could be explored to mitigate potential declines in meat sensory quality. Further research should also address the interactive effects of TMM with heat stress and tropical management conditions, as these factors may modulate both nutrient utilization and sensory responses.
Conclusions
Dietary inclusion of TMM up to 8% in finisher broiler diets was nutritionally feasible, with no adverse effects on growth performance or physicochemical characteristics of breast meat. However, sensory evaluation revealed a threshold effect, with inclusion levels ≥5% significantly reducing juiciness, flavor, tenderness, and texture, whereas appearance and aroma remained unaffected. Although all sensory scores remained within acceptable consumer preference ranges, these findings indicate that sensory quality may become the limiting factor for practical dietary inclusion before nutritional performance is compromised.
If maintaining sensory quality is a priority, dietary TMM inclusion should remain below 5%, or dietary formulation strategies should be explored to mitigate these effects. The observed sensory changes may be associated with ingredient-derived volatiles, lipid composition, amino acid balance, or chitin content, although these mechanisms were not investigated in the present study. Further research should establish practical inclusion limits by integrating carcass composition, fatty acid profiles, postmortem metabolism, stress-related responses, and consumer acceptance. In addition, the partial replacement of soybean meal with TMM may contribute to diversifying protein sources for poultry nutrition and reducing reliance on conventional soybean-derived feed ingredients, thereby supporting the development of more sustainable poultry production systems.
Acknowledgments
Artificial intelligence tools (OpenAI, GPT-4, consulted in August 2025) were used exclusively to assist with English translation and language editing of the manuscript. The authors confirm that all research content, data interpretation, and scientific conclusions are entirely their own responsibility. The authors gratefully acknowledge Universidad Científica del Sur, which made the development and execution of this study possible.
Funding statement
This research was funded by the Seed Fund No. 018-DGIDI-CIENTIFICA-2022 and the Cabieses Scholarship Fund—Funds for Undergraduate and Graduate Thesis Projects 2023-1, both provided by the Universidad Científica del Sur.
Competing interests
The authors declare no competing interests.
Ethical standards
The methods used in this research were approved by the Institutional Committee for Ethics in Research with Animals and Biodiversity of the Universidad Científica del Sur, with the approval certificate 066-CIEI-AB-CIENTÍFICA-2023. The methods used in this research were approved by the Institutional Committee for Ethics in Research of the Universidad Científica del Sur, with the approval certificate 135-CIEI-CIENTÍFICA-2023.
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