Effects of probiotic supplementation in the diet of tilapia (Oreochromis niloticus): A systematic review and meta-analysis

Efeitos da suplementação com probióticos na dieta de tilápia (Oreochromis niloticus): Uma revisão sistemática e meta-análise

Abstract

The objective of this study was to evaluate the effects of dietary probiotic supplementation on weight gain and growth in Nile tilapia (Oreochromis niloticus). To this end, a systematic review with meta-analysis of in vivo experimental studies involving tilapia and the use of probiotics was conducted. Searches were conducted in the Web of Science, Scopus, and ScienceDirect/Elsevier electronic databases. The outcomes observed included weight gain and growth rate. A total of 410 studies were found, of which 7 met the eligibility criteria and were included in the final analysis. In total, the studies evaluated 939 Nile tilapia specimens. The results showed a significant improvement in weight gain of 6.69 g (95 % CI: 4.05–9.34) and in specific growth rate of 27 % (95 % CI: 16 % – 39 %) when compared to the conventional diet. The probiotic strains Leuconostoc mesenteroides + Lactobacillus lactis stood out, inducing an average weight gain of 24 g [22.88 to 25.12] and average growth of 61 % [12 % to 110 %]. It is concluded that probiotic supplementation has the potential to promote significant improvement in weight gain and growth rate in O. niloticus, highlighting its potential as a nutritional strategy in aquaculture.

Keywords:
Weight gain; growth; aquaculture production

Resumo

O objetivo deste estudo foi avaliar os efeitos da suplementação com probióticos na dieta sobre o ganho de peso e o crescimento de tilápias do Nilo (Oreochromis niloticus). Para isso, foi realizada uma revisão sistemática com meta-análise de estudos experimentais in vivo envolvendo tilápias e uso de probióticos. As buscas foram conduzidas nas bases eletrônicas Web of Science, Scopus e Science Direct/Elsevier. Os desfechos observados incluíram ganho de peso e taxa de crescimento. Foram encontrados 410 estudos, dos quais 7 atenderam aos seguintes critérios de elegibilidade que foram, estudos de tilápia (Oreochromis niloticus), tratadas com dieta suplementada com probiótico e que medissem ganho de peso e taxa específica de crescimento e foram incluídos na análise final. No total, os estudos avaliaram 1879 exemplares de tilápias do Nilo, dos quais 939 foram usados no grupo intervenção e 939 como controles. Os resultados demonstraram melhora significativa no ganho de peso de 6,69g (IC 95 %: 4,05–9,34) e na taxa de crescimento específico de 27 %, (IC 95 %: 16 % – 39 %), quando comparados à dieta convencional. Destacou-se o probiótico das cepas Leuconostoc mesenteroides + Lactobacilus lactis que induziram um ganho de peso médio de 24g [22.88 a 25.12] e o crescimento médio de 61% [12 % a 110 %]. Conclui-se que a suplementação com probióticos tem o potencial de promover melhora significativa no ganho de peso e na taxa de crescimento de O. niloticus, evidenciando seu potencial como estratégia nutricional na aquicultura.

Palavras-chave:
Suplementação de peixes; ganho de peso; crescimento; produção aquícola

Resumo

O objetivo deste estudo foi avaliar os efeitos da suplementação com probióticos na dieta sobre o ganho de peso e o crescimento de tilápias do Nilo (Oreochromis niloticus). Para isso, foi realizada uma revisão sistemática com meta-análise de estudos experimentais in vivo envolvendo tilápias e uso de probióticos. As buscas foram conduzidas nas bases eletrônicas Web of Science, Scopus e Science Direct/Elsevier. Os desfechos observados incluíram ganho de peso e taxa de crescimento. Foram encontrados 410 estudos, dos quais 7 atenderam aos seguintes critérios de elegibilidade que foram, estudos de tilápia (Oreochromis niloticus), tratadas com dieta suplementada com probiótico e que medissem ganho de peso e taxa específica de crescimento e foram incluídos na análise final. No total, os estudos avaliaram 1879 exemplares de tilápias do Nilo, dos quais 939 foram usados no grupo intervenção e 939 como controles. Os resultados demonstraram melhora significativa no ganho de peso de 6,69g (IC 95 %: 4,05–9,34) e na taxa de crescimento específico de 27 %, (IC 95 %: 16 % – 39 %), quando comparados à dieta convencional. Destacou-se o probiótico das cepas Leuconostoc mesenteroides + Lactobacilus lactis que induziram um ganho de peso médio de 24g [22.88 a 25.12] e o crescimento médio de 61 % [12 % a 110 %]. Conclui-se que a suplementação com probióticos tem o potencial de promover melhora significativa no ganho de peso e na taxa de crescimento de O. niloticus, evidenciando seu potencial como estratégia nutricional na aquicultura.

Palavras-chave
Suplementação de peixes; ganho de peso; crescimento; produção aquícola

1. Introduction

Tilapia (Oreochromis niloticus), an African cichlid, has gained prominence worldwide in aquaculture due to its high growth performance, resistance to adverse conditions, and adaptability to diverse environments. The search for efficient strategies to improve fish growth and health has led to the application of various feed additives, such as prebiotics and probiotics, which aim not only to optimize weight gain but also to improve feed efficiency and immune resistance (¹, ²).

In the Brazilian context, tilapia farming has established itself as the main pillar of national fish farming, with production that demands constant innovations to maintain competitiveness. However, the production system faces particular challenges, such as the intensification of cage culture and seasonal thermal fluctuations, which favor the incidence of pathogens such as Streptococcus agalactiae. In this context, the integration of additives that promote not only growth but also immune resilience adapted to tropical conditions is imperative for the sustainability of the sector in Brazil.

Recent studies have investigated the effects of these dietary interventions in tilapia, showing promising results in increasing specific growth rate (SGR) and weight gain. More precisely, supplementation with prebiotic compounds has proven to be an effective strategy, promoting significant improvements in growth performance, feed conversion rates (FCR), and nutrient absorption (³, ⁴). Furthermore, the use of these additives has shown positive effects on fish intestinal health, with favorable impacts on intestinal microbial composition and food digestibility.

Studies reveal that dietary supplementation with prebiotics not only improves growth performance but has also shown beneficial results in culture water quality and biochemical parameters of fish (¹). This effect stems from the capacity of probiotics to act as bioremediators: bacteria (especially Bacillus spp.) metabolize toxic nitrogenous compounds such as total ammonia nitrogen (TAN) and unionized ammonia (NH₃), reducing their concentration in water (¹, ³). As advantages, the reduction of environmental stress in fish, lower water renewal requirements, and decreased antibiotic use stand out. As limitations, efficacy depends on the strain, dose, frequency of administration, and culture system employed. Additionally, probiotic supplementation also elevates concentrations of total proteins, albumin, and globulin, indicators of improved immune status in fish (¹,³). This positive impact on overall fish health contributes to disease resistance, which is essential for increasing productivity and reducing veterinary treatment costs.

Consequently, the use of feed additives, such as probiotics, has been consolidating as a sustainable and effective alternative for optimizing productive performance in tilapia culture systems. The adoption of these feeding practices has been increasingly encouraged, as it contributes to aquaculture production efficiency, improves fish health, and offers benefits to the aquatic environment by reducing the need for antibiotics and chemical products. Given this context, this systematic review with meta-analysis, based on analyses of recent studies, brings together the available scientific evidence on the use of probiotics in tilapia farming, with a focus on evaluating growth rate and weight gain in tilapia in response to the inclusion of these feed additives in diets (², ⁴).

2. Material e métodos

This systematic review was conducted in accordance with the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (⁵).

2.1 Eligibility criteria

The protocol for this study was structured based on the PICO methodology (Population of interest, Intervention to be studied, Comparison of the intervention, and Outcome of interest).

Therefore, the PICO framework for this study was as follows: Population of interest: Tilapia (Oreochromis niloticus); Intervention: Diet supplemented with probiotics; Comparison: Conventional diet/without probiotics; Outcome: weight gain, specific growth rate. Only in vivo experimental studies were included in this study, with no restrictions regarding year of publication, language, or availability of the full text.

2.2 Information sources and search strategies

The search strategy was initially developed by two researchers and subsequently reviewed and approved by the entire team. The selected information sources are described in Table 1. The systematic search was conducted in the following electronic databases: Web of Science, Scopus, and ScienceDirect/Elsevier. The filters and Boolean operators used on each platform are detailed in Table 2.

• Web of Science (121 articles)

• Scopus (105 articles)

• ScienceDirect (Elsevier) (184 articles)

Table 1
Boolean operators.

P	I	C	O
· tilapia OR Oreochromis niloticus	probiotic* OR prebiotic* OR symbiotic* OR "feed additive*" OR "dietary supplement" OR "microbial feed"	conventional feed	"weight gain" OR "feed conversion" OR survival OR precocity

Table 2
Boolean operators used on each search platform and filters applied.

Web of science	Scopus	Science Direct
tilapia OR Oreochromis niloticus AND probiotic* OR prebiotic* OR symbiotic* OR "feed additive*" OR "dietary supplement" OR "microbial feed" AND "weight gain" OR "feed conversion" OR survival OR precocity. Filtro: 2024 Filter: 2024	tilapia OR Oreochromis niloticus AND probiotic OR prebiotic OR symbiotic OR "feed additive" OR "dietary supplement" OR "microbial feed" AND "weight gain" OR "feed conversion" OR survival OR precocity. Filter: veterinary	tilapia OR Oreochromis niloticus AND probiotic OR prebiotic OR feed additive AND conventional feed AND weight gain OR feed conversion OR precocity. Filter: 2025, research articles, veterinary science and veterinary medicine, immunology of fish and shellfish.

2.3 Study selection

Data selection and extraction were performed independently by two researchers. To ensure standardization of the process and minimize potential selection biases, the Rayyan platform (Intelligent Systematic Review Platform) was used, an automated tool developed for systematic reviews (⁶).

Initially, studies were screened by reviewing titles and abstracts to identify those that potentially met the eligibility criteria. Next, the full texts of the preselected articles were examined with greater methodological rigor to confirm their inclusion or exclusion. Disagreements that arose during screening or data extraction were resolved by consensus between the two researchers, ensuring the reliability and consistency of the selection process.

2.4 Data collection and investigated outcomes

After selecting the studies, data were collected on the type and dosage of probiotics, control diets, and key outcomes, such as weight gain and growth rate. All studies evaluated tilapia and compared diets supplemented with probiotics to the standard diet. This information allowed us to systematize the effects of supplementation on fish growth and production efficiency, providing a basis for conducting the meta-analysis.

2.5 Risk of bias and quality of evidence

The risk of bias in in vivo experimental studies was assessed using the ROBINS-I (Risk of Bias in Non-randomized Studies of Interventions) tool, recommended by the Cochrane Collaboration for non-randomized intervention studies. This tool examines seven domains of bias, organized according to the stage of the study, as well as other relevant elements, classifying them as low risk, moderate risk, and critical risk (⁷).

2.6 Summary of results and statistical analyses

Quantitative data for continuous variables were summarized using measures of central tendency and dispersion and are presented as means and corresponding percentages, with 95 % confidence intervals. Meta-analyses were conducted using R software (version 4.3.1 for Windows 10), with the meta package (version 6.5.0) (https://www.r-studio.com/pt/).

The choice between fixed-effect and random-effects models was based on an assessment of heterogeneity among the studies. The degree of heterogeneity was measured using the I² test and the p-value. I² values around 25 %, 50 %, and 75 % were interpreted as indicative of low, moderate, and high heterogeneity, respectively. In the presence of low heterogeneity (I² < 10 % and p > 0.05), the fixed-effects model was applied, according to the Mantel-Haenszel method (⁸). In cases of high heterogeneity (I² > 75 % and p < 0.05), the random-effects model was used, following the DerSimonian-Laird method, as proposed by Higgins and Thompson (⁹).

3. Results

Figure 1 shows the flowchart of the study search and selection process. Initially, 410 records were identified, of which 9 were removed prior to screening because they were duplicates or did not meet the preliminary criteria. During the screening phase, 401 records were evaluated, resulting in the exclusion of 376 for reasons such as: inappropriate study design, absence of the outcomes of interest (i.e., the studies did not measure weight gain or specific growth rate), an incompatible target population, or because they were review articles. At the end of this stage, 25 publications were selected for full-text review, of which 14 could not be retrieved (i.e., the full texts were not available in the databases or via institutional access mechanisms). After detailed analysis, 11 publications were assessed for eligibility, and 7 studies were included in the final review because they met all the established criteria.

Figure 1
Flowchart of the study selection process

The characteristics of the included studies are presented in Tables 3 and 4. The overall and subgroup meta-analyses are shown in Figures 2 through 9. The risk of bias is detailed in Figure 10.

The experimental studies involved 1,879 fish, of which 939 were in the intervention group and 939 served as controls, with an emphasis on dietary supplementation with prebiotics and probiotics. The interventions included diets with partial replacement of fish meal, probiotic supplementation, and the use of L. plantarum at 1 × 10⁸ CFU, all of which had positive effects on weight gain and growth performance in the animals (Table 4).

Table 3
General study data.

Author	Country	Persistent identifier	Type of study
Bunkaew et al., 2024 (10)	Thailand	https://doi.org/10.3390/microbiolres15040148	In vivo experimental study
Magouz et al., 2019 (1)	Egypt	https://doi.org/10.26873/SVR-746-2019	In vivo experimental study
Muhammad et al., 2023 (11)	Pakistan	https://dx.doi.org/10.17582/journal.pjz/20220703220755	In vivo experimental study
Naveed et al., 2024 (12)	Pakistan	https://dx.doi.org/10.21162/PAKJAS/24.137	In vivo experimental study
Paritova et al., 2024 (3)	Kazakhstan	https://doi.org/10.1371/journal.pone.0312580	In vivo experimental study
Shija et al., 2025 (2)	China	https://doi.org/10.1016/j.aquaculture.2024.741727	In vivo experimental study
Youssef et al., 2024 (4)	Egypt	https://dx.doi.org/10.5455/OVJ.2024.v14.	In vivo experimental study

Table 4
Summary of Research Results.

Author	Objective	No. of animals	Intervention	Duration (days)	Risk of Bias	Comparator	Weight gain (g)	Taxa de growth (%)	Conclusion
Bunkaew et al., 2024 (10)	To evaluate whether the exopolysaccharide produced by B. subtilis P1, added to the diet, can improve the growth of tilapia	150 fingerlings	Diet supplemented with exopolissacarídeo (EPS) microbiano do Bacillus subtilis P1, included a 5 g/kg de feed (0,5%).	42	High	Basal diet/control withort EPS	Control: 76,15g T1:78,58g	Control: 3,03 T1:3,17	Improvement significant no growth performance e immune response.
Magorz et al., 2019 (1)	To test the effects of dietary supplementation with mannanoligosacchar ides and β-glucans from yeast cell wall at different concentrations on tilapia growth.	315 fingerlings	Supplementation dietry à base de yeast cell wall: Biomos (Bio‑ Mos, MOS) a 0.1%, 0.2%, 0.3% e Agrimos (MOS + β‑ glucanos) a 0.1%, 0.2%, 0.3% na diet basal 30% PB, provided at 3% da biomass/day	105	Moderate	Control diet withort additive	Control: 24,93 ± 0,06g T1: 29,46 ± 0,78g T2: 27,36 ± 0,08g T3: 26,96 ± 1,00g T4: 27,00 ± 1,01g T5: 28,86 ± 0,57g. T6: 25,06 ± 0,86g.	Control: 1,3 ± 0,03 T1: 1,8 ± 0,16 T2: 1,5 ± 0,03 T3: 1,43 ± 0,03 T4: 1,6 ± 0,18 T5: 1,7 ± 0,15 T6:1,40 ± 0,05	Increase no growth performance e immune parameters nos grorps with mannan oligosaccharides e β-glucans.
Muhammad et al., 2023 (11)	To investigate whether dietary supplementation with L. plantarum and P. pentosaceus, alone or in combination, is effective.	120 fingerlings	Diet supplemented with probiotics (Lactobacillus plantarum e/or Pediococcus pentosaceus)	60	High	Diet convencional withort probiotics	Control: 26,33 ± 1,04g T1:30,26 ± 1,27g. T2: 30,80 ± 1,14g. T3: 36,00 ± 1,13g	Control: 2,42 ± 0,02. T1:2,63 ± 0,00. T2: 2,66 ± 0,06. T3: 2,94 ± 0,04.	Improvement no growth e intestinal health with o uso de Lactobacillus plantarum e Pediococcus pentosaceus.
Naveed et al., 2024 (12)	To evaluate whether the partial replacement of fishmeal with soybean meal fermented with L. plantarum, in association with probiotics, maintains or improves tilapia growth.	120 juvenile tilapia	Diets with partial replacement da fish meal por fermented soybean meal with Lactobacillus plantarum (FSBM 25% or 50%) + probiotics Bacillus subtilis e B. licheniformis a 2% or 4% (27×10^9 CFU/g), além de supplementation de lisina (0.5%) e metionina (1%)	120	Low	Basal diet with 100% fish meal withort soybean meal fermentado e withort probiotics	Control: 112,5 ± 1,154g T1: 118,0 ± 1,166g T2: 121,0 ± 0,881g T3: 110,5 ± 1,392g T4: 111,5 ± 1,154g	Control: 2,4 ± 0,029 T1: 2,5 ± 0,066 T2: 2,4 ± 0,05 T3: 2,2 ± 0,011 T4: 2,3 ± 0,057	Improvement no growth e na digestive enzyme activity nos grorps supplemented with 25% FSBM e 4% probiotics.
Paritova et al., 2024 (3)	To investigate the effects withbined of two probiotic strains (L. mesenteroides e L. lactis) on growth.	384 tilapia	Diets experimentais supplementeds with probiotics LAB isolados de fish: L. mesenteroides (LM), L. lactis (LL) e mixture LM+LL, incorporated à basal feed a 1 × 10^7 CFU/g, provided twice/day	56	Moderate	Basal diet withort probiotic	Control: 68,4 ± 3,26g T1:79,2 ± 1,16 g T2: 78,5 ± 2,15 g T3: 92,4 ± 4,54 g	Control: 1,96 ± 0,11 T1:2,32 ± 0,5 T2: 2,30 ± 0,3 T3: 2,82 ± 0,2	Indica results positive no growth, intestinal health e immunity with Lactobacillus e Pediococcus.
Shija et al., 2025 (2)	To determine the effect of different doses of B. amyloliquefaciens AV5 on growth on tilapia.	360 tilapia	Diet supplemented with Bacillus amyloliquefaciens AV5 derivado do intestino do hospedeiro; doses 10^6 CFU/g (G1) e 10^8 CFU/g (G2); feeding twice/day a 3% do peso por 30 days	30	Moderate	Commercial diet withort probiotic	Control: 46,82 ± 0,4g T1:47,33 ± 0,2g T2: 59,37 ± 0,7g	Control: 2,22 ± 0,2 T1:2,53 ± 0,2% T2: 3,27 ± 0,1	Increase no growth, na immune response e disease resistance with Bacillus amyloliquefaciens AV5.
Yorssef et al., 2024 (4)	To evaluate the impact of supplementation with a probiotic, B. amyloliquefaciens in different doses on growth of tilapia.	120 fingerlings	Supplementation dietry with probiotic Bacillus amyloliquefaciens (Ecobiol) a 1, 2 e 3 g/kg de feed.	120	Moderate	Basal diet withort probiotic (G1), same culture conditions	Control: 47,0 ± 2,9g T1:59,8 ± 5,9g T2: 62,9 ± 3,7g T3: 63,5 ± 3,1g	Control: 0,42 ± 0,1 T1:0,59 ± 0,1 T2:0,63 ± 0,1 T3: 0,64 ± 0,1	Improvement no feeding behavior, growth e biochemical parameters nos grorps with Bacillus amyloliquefaciens.

• The metaanalysis evaluated the effects of dietary supplementation with probiotics on total weight gain and specific growth rate of Oreochromis niloticus. Data from eight experimental studies were integrated. Overall, a positive and statistically significant effect was observed in both zootechnical performance parameters. The heterogeneity among the included studies was substantial.

3.1 Results on weight gain

Weight gain (Figure 2 and table S1) indicated a significant and positive effect of probiotic or prebiotic use compared to the control group. The random effects model demonstrated a weighted mean difference (MD) of 6.69g [95 % CI: 4.05; 9.34], with heterogeneity (I² = 99.6 %; p < 0.001), evidencing considerable variation among the included studies. Despite the heterogeneity, the overall effect remained statistically significant (p < 0.0001), indicating that probiotic supplementation contributed to increased average weight of tilapia.**

Figure 2
Forest plot of the meta-analysis comparing probiotics versus control for weight gain (g). Effects are expressed as mean difference (MD) with 95 % CI, estimated by random effects model. The overall effect favored the use of probiotics (MD = 6.69; 95 % CI: 4.05–9.34), with high heterogeneity (I² = 99.6 %).

When results were stratified by maturity stage (Figure 3), a significant difference was observed between subgroups (χ² = 11.99; df = 2; p = 0.0025), suggesting that the physiological age of fish influences the magnitude of the probiotic response. In juvenile fish, the random effects model demonstrated a weighted mean growth of 7.05 [95 % CI: 3.87; 10.22], demonstrating superiority over other maturity stages. In early stages (larvae and post-larvae), I² = 99.2 % and τ² = 96.68 indicate that, although there is a positive response, there is strong variation among experiments. These findings indicate that maturity acts as a relevant moderator, and younger fish, with more plastic metabolism, tend to show superior responses to probiotic supplementation.

Figure 3
Forest plot of the meta-analysis comparing probiotics versus control, with subgroup analysis by life stage (juveniles, fingerlings, and adults). Effects are presented as mean difference (MD) with 95 % CI, estimated by random effects model. The overall effect favored probiotics, with high heterogeneity and significant differences between subgroups.

When studies were grouped according to experimental duration (Figure 4), there was no linear development with treatment duration, with an intermediate time of 56 days demonstrating the best result for mean weight gain when compared with other time periods, being 14.96 [95 % CI: 6.11; 23.81]. These results do not contradict that probiotic supplementation requires longer periods of exposure to fully express its physiological effects; however, they demonstrate that other factors may be more preponderant for this, such as the type of strain used in the supplementation.

Figure 4
Forest plot of the meta-analysis evaluating the effect of probiotic supplementation compared to the control group, stratified by treatment time (tt, in days). Effects are expressed as mean difference (MD) with 95 % confidence intervals (95 % CI), estimated by random effects model. Each square represents the individual effect of a study, with size proportional to statistical weight, and horizontal lines indicate the 95 % CI. The blue diamonds represent the combined effects within each time subgroup and the overall effect.

The meta-analysis stratified by probiotic strain demonstrated expressive differences between formulations (Figure 5). Leuconostoc mesenteroides + Lactobacillus lactis induced greater weight gain among all strains found 24.00 % [22.88:25.12]. Overall, multispecies formulations and probiotics based on Bacillus and Lactobacillus showed more consistent responses. The high variations in heterogeneity suggest that strain type, dose, and administration form are critical determinants of the magnitude of effect. Subgroup tests revealed high and highly significant χ² statistics (χ² = 32.34; df = 5; p < 0.0001; and χ² = 1120.18; df = 10; p < 0.0001).

Figure 5
Forest plot of the meta-analysis evaluating the stratified effect of different probiotic strains. Effects are expressed as mean difference (MD) with 95 % confidence intervals (95 % CI), estimated by random effects model.

3.2 Results on growth rate

With regard to specific growth rate (Figure 6 and Table S2) also showed a significant difference in favor of the group treated with probiotics, with a mean difference (MD) of 0.27 [95 % CI: 0.16; 0.39]. As in the previous analysis, high heterogeneity was observed (I² = 99.7 %; p < 0.001), but the overall effect was statistically significant (p < 0.0001), reinforcing the efficacy of probiotics in improving the productive performance of fish.

Figure 6
Forest plot of the meta-analysis comparing probiotics versus control for growth in percentage (%). Effects are expressed as mean difference (MD) with 95 % CI, estimated by random effects model. The overall effect favored the use of probiotics (MD = 0.27; 95 % CI: 0.16–0.39), with high heterogeneity (I² = 99.7 %).

When growth results were stratified according to maturity stage (Figure 7), a statistically significant difference was observed between subgroups (χ² = 6.93; df = 2; p = 0.0312). In fish in early stages (fry), the values of mean growth rate were 0.32 [95 % CI: 0.13; 0.52].

Figure 7
Forest plot of the meta-analysis comparing probiotics versus control for growth in percentage (%) by maturity stage. Effects are expressed as mean difference (MD) with 95 % CI, estimated by random effects model. The overall effect t favored the use of probiotics (MD = 0.27; 95 % CI: 0.16–0.39), with high heterogeneity (I² = 99.7 %).

Regarding experimental duration (Figure 8), the behavior of growth rate resembled that observed for weight gain, showing no linear relationship with treatment time. The 30-day period recorded the highest mean growth (0.68 [95 % CI: 0.04; 1.41]), suggesting that the efficacy of supplementation may be influenced more by strain specificity and life stage than strictly by the duration of exposure to probiotics.

Figure 8
Forest plot of the meta-analysis comparing probiotics versus control for growth in percentage (%) by supplementation period. Effects are expressed as mean difference (MD) with 95 % CI, estimated by random effects model. The overall effect favored the use of probiotics (MD = 0.27; 95 % CI: 0.16–0.39), with high heterogeneity (I² = 99.7 %).

When the analysis for growth was conducted by probiotic strain type (Figure 9), the results revealed, as with weight gain, that the combined strain of Leuconostoc mesenteroides + Lactobacillus lactis induced greater growth among all strains found 0.61 [0.12:1.10]. Overall, multispecies formulations and probiotics based on Bacillus and Lactobacillus showed more consistent responses. The high variations in heterogeneity suggest that strain type, dose, and administration form are critical determinants of the magnitude of effect. The subgroup test (χ² = 2904.43; df = 10; p = 0) showed significant differences between probiotics, suggesting that the type of bacterial strain is the main determinant of the magnitude of growth gain. Overall, probiotics based on Lactobacillus and Bacillus showed more consistent and expressive results, possibly due to their greater capacity for intestinal colonization, production of digestive enzymes, and immune modulation.

In summary, the combined analysis of growth data reveals that, although statistical heterogeneity is high (I² > 90 %), the effect of probiotic supplementation on the species is consistently positive and biologically relevant. This variability stems from methodological and biological disparities among experiments, with emphasis on the diversity of strains, periods of exposure, and physiological stages of fish. However, the convergence in the direction of estimates reinforces the reliability of the outcome, indicating that the inclusion of probiotics optimizes the growth rate of O. niloticus, especially in long-duration protocols and with the use of strains metabolically adapted to the host.

Figure 9
Forest plot of the meta-analysis comparing probiotics versus control for growth in percentage (%) by strain type. Effects are expressed as mean difference (MD) with 95 % CI, estimated by random effects model. The overall effect favored the use of probiotics (MD = 0.27; 95 % CI: 0.16–0.39), with high heterogeneity (I² = 99.7 %).

Regarding risk of bias (Figure 10), most studies presented low risk, with emphasis on Youssef et al. (⁴). However, the study by Muhammad et al. (¹¹) presented high risk of bias in critical domains, such as the absence of detailed description of specimen randomization and lack of blinding in the measurement of zootechnical outcomes. Such methodological limitations demand cautious interpretation, as they may overestimate the positive effects observed and compromise the overall reliability of the results.

Figure 10
Risk of bias of the studies included in the analysis.

4. Discussion

Overall, the results of the meta-analysis suggest that the addition of probiotics and prebiotics to the diet led to significant improvements in the zootechnical performance of Oreochromis niloticus, evidenced in weight gain and growth rates. These results are in agreement with the literature, which highlights beneficial microorganisms as effective nutritional tools to increase the productivity of farmed fish (¹, ⁴, ¹³). Thus, probiotic supplementation emerges as a promising approach to improve the productive performance of the species.

Although the overall average weight gain with probiotic use was 6.69 grams per fish, some specific formulations stood out, showing considerably higher effects. The combination of Leuconostoc mesenteroides and Lactococcus lactis, for example, demonstrated an increase of approximately 24 g, a value significantly higher than the average recorded in the studies. This result can be attributed to the synergistic action of strains highly adaptable to the intestinal tract, which produce more short-chain fatty acids and better stimulate enzymatic and immunological activity, thus increasing feed conversion efficiency (³). Similar research indicates that multispecies formulations have a greater impact compared to isolated strains (¹⁴,¹⁵), highlighting the relevance of well-organized microbial consortia.

The synergism between L. mesenteroides and L. lactis stems from metabolic complementarity: while L. lactis produces lactic acid and nisin, bacteriostatic compounds that reduce intestinal pH and inhibit Gram-negative bacteria, L. mesenteroides synthesizes exopolysaccharides and volatile organic acids that favor the adhesion and nutrition of other beneficial bacteria. This interaction creates an acidic and stable microenvironment, increasing digestive efficiency and nutrient absorption. In the study by Maqbool (¹⁶), the L. mesenteroides NM12 strain showed broad antimicrobial activity and high hydrophobicity (60.5 %) and mucus adhesion (39.8 %), while L. lactis NM951 showed excellent acid resistance and tolerance to bile salts, suggesting that the combined use of these species improves intestinal balance and feed utilization, conditions that favor growth and feed conversion also in tilapia. From the perspective of immune response and resistance, the immunomodulatory effects of these strains were documented by Balcázar (¹⁷), who observed a significant increase in lysozyme activity, an enzyme that acts in the lysis of the cell wall of pathogenic bacteria, and the alternative complement pathway (ACH₅₀), which reflects the activation of a group of serum proteins responsible for opsonization and direct destruction of invaders. Notably, these immunological responses remained elevated for a period of 15 days after the end of supplementation. These parameters are crucial indicators of innate immunity activation, which represents the first line of defense in aquaculture species.

Furthermore, Bacillus amyloliquefaciens, especially at a concentration of 10⁸ CFU/g, stood out in both weight increase and growth rate. This strain is known for generating digestive enzymes, such as proteases and amylases, as well as bioactive metabolites with immunomodulatory effects, aiding in the maintenance of intestinal integrity and optimization of nutrient absorption (²). Mohapatra (¹⁸), reporting similar results, observed significant improvements in the performance of tilapia supplemented with Bacillus species. This reinforces the use of this microorganism as a possible growth promoter.

In contrast to the expressive results of probiotics, supplementation with isolated amino acids, such as lysine and methionine, showed a lower magnitude of effect on zootechnical performance. Although essential, these compounds do not directly act on the modulation of intestinal microbiota or the activation of immunological pathways, as observed in microbial treatments (¹⁴). Furthermore, it is important to emphasize, as discussed previously in the analysis of inclusion criteria, that nutritional imbalances or suboptimal feeding conditions can induce hepatic metabolic overload (¹⁹). This factor, combined with the absence of stimulation to innate immunity, explains why the results of this specific intervention fell below the expectations observed for the probiotic groups in this meta-analysis.

Beyond the increase in biomass, the benefits of probiotic supplementation extended to growth rates, evidencing that these microorganisms influence not only body composition but also the pace of metabolic development. The pooled mean difference of 0.27 confirms a significant effect, even under high experimental variability. Formulations containing Bacillus amyloliquefaciens and the consortium Leuconostoc mesenteroides + Lactococcus lactis showed the most expressive performances, demonstrating high colonization potential and activation of anabolic pathways associated with increased body structure (²,³). Muhammad et al. (¹²) reported similar findings, with an increase in specific growth rate in tilapia subjected to treatment with Lactobacillus plantarum, which reflects greater efficiency in feed conversion.

The physiological processes that elucidate this performance encompass the modulation of intestinal microbiota, expansion of endogenous enzymatic activity, improvement of intestinal mucosa integrity, and reduction of oxidative stress, elements that directly affect the absorption of amino acids and fatty acids (²⁰, ²¹). In this scenario, supplementation with probiotics seems to stimulate synergistic processes between metabolism, digestibility, and immunocompetence, which explains the consistency of the observed results (⁴).

The subgroup analysis revealed that, although the age of fish, the duration of supplementation, and the type of probiotic did not alter the positive direction of benefits, these factors directly influenced the amplitude of results. Specimens in early stages of development showed more pronounced gains, which can be attributed to the high adaptive competence of the digestive and immune system in formation (³). Additionally, interventions lasting 60 days or longer exhibited greater data stability, suggesting that the consolidation of exogenous microbiota and subsequent physiological modulations require a maturation period for their full expression (²). Thus, such variables act as moderating factors that optimize the zootechnical response, without compromising the viability of using probiotics as a nutritional strategy.

The critical analysis of the reviewed studies reveals that the superiority of certain strains, such as Bacillus amyloliquefaciens, stems from its enzymatic robustness, which is strategically relevant for the intensive farming systems predominant in Brazil. While international literature focuses on controlled conditions, national studies (¹⁹) reinforce that the efficacy observed in this meta-analysis is potentiated when the probiotic acts as a modulator of intestinal health in the face of management stress. Therefore, the transition from a merely descriptive approach to the understanding of synergistic mechanisms allows us to conclude that probiotic supplementation is a viable technology transfer tool to mitigate gaps in feed efficiency and reduce the dependence on chemotherapeutics in national aquaculture.

When comparing the studies, inconsistencies are observed in the magnitude of response to the Bacillus genus. While Shija et al. (²) reported expressive increments, Naveed et al. (¹¹) observed more discrete effects under protein substitution conditions. This divergence suggests that probiotic efficacy is not intrinsic only to the strain, but modulated by the composition of the basal diet and the stress level of the system. Such methodological variations, although generating high statistical heterogeneity (I² > 99 %), show that the zootechnical benefit is maximized when the probiotic acts in synergy with nutritional management, and not as an isolated additive.

The high heterogeneity (I² > 99 %) identified in the analyses can be explained by variations in experimental protocols, including dietary formulations, strains employed, duration of treatment, and environmental farming conditions, such as stocking density, water temperature, dissolved oxygen levels, and management systems (biofloc vs. recirculation) (²¹). However, the consistency in the direction of effect suggests that this variability is a reflection of methodological disparities inherent to aquaculture, without compromising the reliability of overall results.

The integration of these findings allows for the establishment of a conceptual framework for the use of probiotics in O. niloticus. The process begins with competitive colonization of the intestinal epithelium, which promotes villus integrity and expands the absorption area. Simultaneously, the secretion of exogenous enzymes (amylases and proteases) by Bacillus strains optimizes the breakdown of macromolecules, resulting in improved feed conversion and acceleration of metabolic development rate. This integrative model explains why, despite differences between experiments, the direction of effect remains consistently positive, consolidating probiotics as pillars of an efficient and sanitarily safe productive system.

The mechanisms of action that support these results involve the production of digestive enzymes (amylases and proteases) and the synthesis of bacteriostatic compounds, such as nisin. However, it is necessary to acknowledge the limitations of the reviewed studies: the high statistical heterogeneity (I² > 99 %) and the risk of bias in domains such as blinding and allocation suggest that positive effects may be overestimated under controlled experimental conditions. This gap between the laboratory and the field is one of the main barriers to the standardization of protocols in tilapia farming.

In summary, the results of this systematic review with meta-analysis indicate that supplementation with probiotics constitutes an effective strategy to optimize weight gain and accelerate the growth rate of O. niloticus, with emphasis on strains of the Bacillus and Lactobacillus genera. This efficacy is potentiated by the use of multispecific formulations and protocols lasting a minimum of 60 days. Although the pooled mean effect is moderate, specific strains demonstrated superior zootechnical performances, which reinforces their viability for application on a commercial scale. In contrast, isolated supplementation of amino acids (lysine and methionine) did not replicate such benefits, evidencing that the integrity and modulation of microbiota are determinants for efficiency in nutrient absorption. Given this scenario, it is recommended that future studies adopt standardized experimental designs and long-term evaluations, aiming to consolidate the practical applicability of the tested protocols.

The practical implications for the productive sector are direct: supplementation with Bacillus and Lactobacillus presents itself as a viable strategy to reduce the feed conversion ratio. However, we identified a critical knowledge gap: the scarcity of studies evaluating the persistence of these strains in open systems, such as the net pens predominant in Brazil, where feed leaching and interaction with environmental microbiota are constant. Future research should focus on validating these protocols on a commercial scale, aiming to transform the biological potential observed in this meta-analysis into real economic gains for the producer.

Ultimately, the transition from a merely descriptive review to an analytical synthesis allows us to understand that probiotic supplementation in O. niloticus is a multifactorial tool. The observed efficacy should not be dissociated from the reality of production systems, especially in Brazil, where intensification and sanitary challenges require nutritional solutions that ensure biosecurity. By identifying methodological gaps and inconsistencies in zootechnical performances, this work not only systematizes current knowledge but establishes the foundation for future research and the national productive sector to standardize protocols for probiotic use, transforming scientific evidence into productivity and sustainability gains for Brazilian aquaculture.

5. Conclusion

In sum, the evidence gathered in this review suggests that probiotic supplementation in the diets of Oreochromis niloticus produces significant and positive effects with regard to weight gain and growth rate. The findings indicate that the addition of probiotics, especially strains of the Bacillus and Lactobacillus genera, is a viable nutritional option to improve the productive performance of tilapia species, provided that appropriate formulations and management protocols are adopted and that supplementation lasts a minimum of 60 days. However, due to the limitations of the studies included in this systematic review, the variation in doses, administration times, and the age of fish require careful consideration in the interpretation of the results obtained. For this reason, it is suggested that future studies use more robust designs, favoring the reliability of estimates and minimizing publication bias.

Supplementary materials

Supplementary material (available online only: https://revistas.ufg.br/vet/article/view/84820)

Table S1. Spreadsheet showing weight gain in grams for Oreochromis niloticus treated with probiotics.

Table S2. Spreadsheet showing the growth in centimeters of Oreochromis niloticus treated with probiotics.

Supplementary material

Data availability statement

The complete dataset supporting the results of this study was published in the article itself and in the supplementary material.

Generative AI use statement

The authors did not use any generative artificial intelligence tools or technologies in the creation or editing of any part of this manuscript.

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*

corresponding author: [e-mail]

Conflict of interests

The authors declare no conflict of interest.

Editor:

Rondineli P. Barbero

Publication Dates

• Publication in this collection
  26 Oct 2026
• Date of issue
  2026

History

• Received
  06 Jan 2026
• Accepted
  07 July 2026
• Published
  02 Sept 2026