Germination and Drying as a Traditional Processing Method for Soybean Incorporation in Fish Feed in Togo ^†

Abstract

The effects of germination (fresh germinated soybean [SG1F]) and post-germination drying (dried germinated soybean [SG1S]) on the crude protein (CP) levels, aflatoxin content, survival, and growth performance of Nile tilapia fry (Oreochromis niloticus) were evaluated. Raw soybean (SC) and roasted soybean (ST) served as controls. Laboratory analyses revealed CP contents of 11.74%, 38.72%, 38.42%, and 34.72% for SG1F, SG1S, RT, and RS, respectively. Aflatoxin levels were 2.3 µg/kg for SG1S, 1.66 µg/kg for RS, 1.60 µg/kg for RT, and 0.00 µg/kg for SG1F. Experimental diets, formulated to be isoproteic (35.44%) and isolipidic (8.73%), were prepared using flour from these soybean treatments and tested on tilapia fry with an average initial weight of 11.86 ± 2.15 g. The study was conducted in a completely randomized design with three replicates in 1 m³ tanks stocked at 35 fry per tank over 56 days. Weight gains were 23.40 ± 10.21 g, 18.93 ± 8.67 g, 16.30 ± 9.92 g, and 16.07 ± 5.55 g for RT, RS, SG1S, and SG1F, respectively. Survival rates were 100%, 90.67%, 89.33%, and 88% for SG1F, RS, RT, and SG1S, respectively. Daily growth rates showed a consistent upward trend for all diets from the start to the end of the experiment.

1. Introduction

Aquaculture is arguably the fastest-growing food production sector, accounting for nearly 52% of global fish consumption and seen as a key solution to meeting the rising demand for aquatic products. It plays a significant role in food security and nutrition in the 21st century [1]. In Togo, aquaculture contributes only 5.08% of national fish production. However, total fish production—both from aquaculture and capture fisheries—meets just 30% of the country’s domestic output [2], despite Togo’s natural potential for aquaculture development [3]. Tilapia farming (genus Oreochromis) dominates, primarily in semi-intensive systems [4,5]. Thus, improving local aquaculture production is critical to reducing dependence on declining marine fisheries and imports.

Accelerating the adoption of sustainable and equitable aquaculture practices requires advancing policies, management, investments, and innovation [1]. Feed, a critical link accounting for 60–70% of production costs, is a priority area for technological innovation [6], as it significantly influences fish farm productivity. Fishmeal is the primary protein source in aquafeed [7,8], but its rising cost drives the need for alternative protein sources.

Scientific efforts to improve tilapia feed have focused on valorizing agricultural by-products [3,4,5,9,10]. However, alternative soybean (Glycine max) processing methods, such as dormancy breaking through water soaking, remain underexplored. Soybean, rich in digestible proteins, has superior nutritional value compared to cereal proteins [11,12], making it the second-most important protein source in fish feed after fishmeal. However, soybeans contain antinutritional compounds like tannins, saponins, phytic acid, protease inhibitors, gossypol, and aflatoxins [13,14].

Dormancy-breaking techniques aim to enhance protein bioavailability while reducing antinutritional factors, offering an alternative to roasting, which is cost-intensive and can degrade nutritional quality if poorly managed.

This study aims to improve aquaculture productivity in Togo through alternative soybean processing methods for sustainable fish feed. Specifically, it evaluates the effects of germination and post-germination drying on crude protein content and aflatoxin levels in soybeans. Additionally, it conducts a preliminary assessment of diets incorporating germinated and dried soybeans on the growth performance of Nile tilapia fry (Oreochromis niloticus).

2. Methodology

2.1. Study Area

Soybean samples were sourced from local markets and feed mills in Lomé. Bromatological analyses were conducted at the Food Quality Control Laboratory of ITRA, and feeding experiments were performed at the Agbodrafo Fisheries Research Station (SRHA) from 2 December 2020 to 15 May 2021. SRHA is situated in the Maritime Region under the Togolese Institute for Agronomic Research (ITRA), affiliated with the Ministry of Agriculture, Livestock, and Rural Development (MAEDR).

Located in a tropical Guinean climate, Agbodrafo experiences four seasons: a major dry season (November–March), a major rainy season (March–July), a minor dry season (August–September), and a minor rainy season (September–November). Average annual temperatures are 26.9 °C, with March being the warmest month (28.5 °C) and August the coolest (25 °C). Average annual rainfall is 888 mm, with the region’s hydrographic network dominated by three rivers (Zio, Haho, and Boko), draining into Lake Togo [15].

2.2. Study Materials

The biological material primarily consisted of mixed-sex juveniles of Nile Tilapia (Oreochromis niloticus) from the Akosombo strain, with an average weight of 11.86 ± 2.15 g, sourced from the Fisheries Research Station in Agbodrafo.

2.3. Methods

2.3.1. Soybean Sample Collection

For this study, ten soybean samples were collected, comprising five samples of roasted soybeans and five samples of raw soybeans. These were sourced from the five largest sales outlets in Lomé and soybean collectors from major production areas. Composite samples were then created by combining equal quantities of the collected soybeans to mitigate regional variability in soybean composition due to environmental and agricultural practices [16].

2.3.2. Soaking and Dormancy Break in Soybean Sample Processing

The germination process for sprouted soybean treatments was scheduled to ensure all samples were analyzed on the same day (day 8,

Table 1. Chronogram of the soybean germination process.

Day 1	Day 2	Day 3	Day 4	Day 5	Day 6	Day 7	Day 8
Soaking	Incubation	Germination	Drying	Drying	Drying	Drying	Stop
Sample 1	Sample 1	Sample 1	Sample 1	Sample 1	Sample 1	Sample 1	Sample 1
	Soaking	Incubation	Germination	Stop
	Sample 2	Sample 2	Sample 2	Sample 2

).

Two raw soybean samples (200 g each) were soaked in separate trays containing 1.232 L of water at an average temperature of 31 °C for 24 h. After soaking, the soybeans were drained and incubated for dormancy breaking. Over three days, the seeds were spread on moistened cloth and covered with similar material. Monitoring involved temperature checks and periodic water sprays to replicate traditional methods.

Upon tegument emergence, the first sample was removed on day 4 and air-dried at an average temperature of 31.68 °C to produce dried sprouted soybeans by day 8 (Figure 1). A second batch was soaked on day 5 to ensure fresh sprouted soybeans on day 8.

To achieve this, two (02) raw soybean samples, each weighing 200 g, were soaked in two containers, each containing 1.232 L of water, for 24 h at an average temperature of 31 °C. After 24 h, the seeds were removed from the water for draining and incubation. The dormancy-breaking process lasted three (03) days, during which the soybean seeds were spread on a water-moistened cloth and covered with the same type of fabric. Monitoring involved measuring the temperature until the complete emergence of the seed coats, while regularly sprinkling water to simulate the traditional dormancy-breaking process.

After the seed coats had fully emerged, the first sample was removed on Day 4 for drying at an average ambient temperature of 31.68 °C, resulting, on Day 8, in soybean sprouts dried one (01) day after germination (Figure 1).

A second batch of raw soybeans was started on Day 5 for germination, ensuring that the complete emergence of seed coats from this batch coincided with the eighth day of the first batch. This process yielded fresh soybean sprouts one day after germination, under an average ambient temperature of 31 °C.

2.3.3. Laboratory Analyses

Sample Preparation

Soybeans subjected to various treatments and fishmeal were analyzed in the laboratory. A total of nine (09) samples were prepared, labeled, and transported to the ITRA quality control laboratory for bromatological analysis and aflatoxin detection (

Table 2. Samples prepared for analysis.

Number	Samples	Bromatological Analyses	Aflatoxin Detection
1	Fresh germinated soybean (1 day)	1	1
2	Dried germinated soybean (1 day)	1	1
3	Raw soybean	1	1
4	Roasted soybean	1	1
5	Fishmeal	1	-

).

Determination of the Chemical Composition of Soybean Samples and Aflatoxin Detection

The analyses focused on determining the moisture content, organic components (proteins, lipids, and carbohydrates), and mineral content (ash) of soybean samples and fishmeal. The detection and quantification of aflatoxins in soybean samples were conducted using the standard AOAC (Association of Official Analytical Chemists, VICAM kit, number 991.31, September 2010 version) method for all soybean samples. The methods employed are summarized in

Table 3. Analytical methods used in the laboratory.

Type of Analysis	Methods
Physico-chemical characteristics (%w/w)
Moisture content	NF ISO 11294
Protein content	NF V 03-050
Ash content	NF ISO 7514
Lipid content	NF V 03 924
Carbohydrate content	CAC/vol. IX ed. 1
Aflatoxin detection (µg/kg)
Aflatoxin quantification	AOAC

.

2.3.4. Feed Formulation

Selection of Ingredients

A list of 30 ingredients derived from databases on aquaculture feed formulation [17,18,19] was used. Based on this list, the ingredients were selected based on their availability in Togo [3,4]. The composition of crude protein, lipids, and metabolizable energy of the raw materials used is presented in

Table 4. Raw material incorporation rates.

Ingredients	Incorporation Rate (%)
	SG1F	SG1S	SC	ST
Maize	5	5	5	5
Broken rice	10	10	10	10
Cubed bran	7.5	7.5	7.5	7.5
Soybean cake	19.5	19.5	19.5	19.5
Groundnut oil	3	3	3	3
Growth concentrate 5%	2	2	2	2
DL-Methionine (99%)	0.5	0.5	0.5	0.5
Soybean	30	30	30	30
Fishmeal	22.5	22.5	22.5	22.5
Total	100	100	100	100
Theoretical Chemical Composition
Crude protein (PB, %)	35.44	35.44	35.44	35.44
Crude lipids (LB, %)	8.73	8.73	8.73	8.73
Digestible energy (ED, kcal/kg)	2931.52	2931.52	2931.52	2931.52

SG1F: Diet containing fresh 1-day germinated soybean; SG1S: diet containing dried 1-day germinated soybean; SC: diet containing raw soybean; ST: diet containing roasted soybean; PB: crude protein; LB: crude lipids; ED: digestible energy.

.

According to Ranirinaharilala [20], feed formulation involves calculating ingredient proportions to meet the nutritional needs of the target species while optimizing cost. In this study, an Excel-based programming model using the “Solver” add-in, developed by the research team at the Agbodrafo Fisheries Research Station [9], was employed to formulate iso-protein diets. This model optimizes feed cost and quality by utilizing agro-industrial products and by-products. The soybean treatments were incorporated uniformly at a rate of 30%. However, for germinated soybean, the fresh weight obtained after germination was used to prevent excess moisture, which complicates pellet molding, as 100 g of raw soybean nearly doubles in weight after germination. The cassava mash was fixed at 10% to meet gelatinization needs.

2.3.5. Production of Experimental Feeds

Preparation of Ingredient Batches for Feed Formulation

A total of four (04) experimental diets were formulated for fish, incorporating different soybean treatments: roasted soybean composite (ST), fresh germinated soybean composite (1 day after sprouting) (SG1F), dried germinated soybean composite (1 day after sprouting) (SG1S), and raw soybean composite (SC). The control diet contained roasted soybean composite.

Feed Processing

Ingredients were sequentially ground using a mill, with cleaning between batches to prevent cross-contamination. Soybean samples were ground just before feed production to ensure immediate use. Macro-ingredients (maize, soybean, roasted soybean, wheat bran, fishmeal) were weighed with a 1 g precision digital scale, while micro-ingredients (growth concentrate, methionine, and shell powder) were measured with a 0.01 g precision scale, following a predetermined formulation. The mixing process involved five steps: (i) blending macro-ingredients, (ii) mixing micro-ingredients, (iii) combining both, (iv) incorporating heated cassava mash for granulation, and (v) adding groundnut oil. A manual machine with a 3 mm mesh shaped the feed into strands, which were sun-dried at ~35 °C for two days, followed by shade-drying at ~30 °C. The dried feed was crushed into pellets for ease of feeding. To prevent storage-related degradation, feed was produced weekly based on estimated requirements.

Packaging

The feed was packaged in sacks and stored on laboratory workbenches. The sacks were exposed to sunlight every two days to prevent mold development.

2.3.6. Testing of Experimental Feeds

Experimental Setup

The experimental design used was a triplicate system comprising 12 above-ground tanks of identical volume (1 m³ each), arranged in two rows on a concrete platform separated by a drainage channel. Each tank was equipped with two pipes: an inlet pipe located laterally at the top with perforations at the base, and an outlet pipe situated at the bottom, externally elevated. Water was supplied through an open system based on the principle of communicating vessels, where used water was evacuated from the base while fresh water was introduced at the top. The entire system was housed in a well-ventilated building (Figure 2). The allocation of different feed regimes to the tanks was undertaken randomly.

Stocking

Stocking was carried out at a density of 35 juveniles per m³ per tank, with juveniles averaging 11.86 ± 2.15 g in weight, totaling 420 juveniles across the 12 tanks.

Fish Feeding

Fish feeding commenced three (03) days after stocking to allow the fish to completely empty their stomachs and acclimate to their new environment. The fish were hand-fed to satiation with the formulated feed three times daily (08:00, 12:00, and 16:00) for 56 days. Water inflow was interrupted during feeding.

Tank Maintenance

Tank maintenance was carried out twice weekly by lowering the outlet pipes to remove waste and decomposed feed residues. On sampling days, tanks were completely emptied and cleaned.

Sampling

Four (04) samplings were conducted during the experiment, the first 14 days after stocking, and subsequently every 14 days to assess juvenile growth performance (weight). Fish were starved the day before sampling, and individual weights were systematically recorded.

2.3.7. Data Collection

Data collection involved the regular monitoring of water quality parameters and growth performance of juveniles.

Measurement of Physico-Chemical Parameters of Water

Water quality parameters were measured twice weekly, on Mondays and Thursdays/Wednesdays before feeding, over eight weeks. Parameters assessed included pH, dissolved oxygen, salinity, turbidity, and temperature to evaluate water quality.

Measurement of Juvenile Growth Performance

Juvenile growth performance (weight) was assessed every 14 days during sampling.

• Growth and survival parameters

The following parameters were calculated:

Weight Gain (WG): The difference between final weight (Wf) and initial weight (Wi):

WG = Wf − Wi

Survival Rate (SR): The ratio of final (Nf) to initial (Ni) fish numbers, expressed as a percentage:

SR = 100 × (Nf/Ni)

Specific Growth Rate (SGR, %/day): The daily weight increase as a percentage of body weight, independent of fish size: SGR = 100 × [(lnWf − lnWi)/t] (t = duration of feeding)

Daily Growth Rate (DGR): Evaluates growth speed, calculated as daily weight gain:

DGR = (Wf − Wi)/Δt

(Δt = duration in days)

• Feed utilization parameters

Feed Conversion Ratio (FCR): The ratio of feed intake to biomass gain over a given period:

FCR = Qa/(Bf − Bi)

Feed Efficiency Ratio (FER): The reciprocal of FCR, representing weight gain per unit of dry feed:

FER = 1/FCR or (Bf − Bi)/Qa

2.3.8. Statistical Analysis of Collected Data

Data were entered into an Excel spreadsheet and analyzed using SPSS (version 22) for mean and standard deviation calculations. A one-way ANOVA (p ≤ 0.05) was conducted to evaluate treatment significance, followed by Duncan’s test to identify significant differences between group means.

3. Results

3.1. Chemical Composition of Soybean Samples

The results of the chemical characteristics of the soybean samples, including moisture content, protein, lipid, ash, and carbohydrate levels, are presented in

Table 5. Physicochemical characteristics of the different soybean treatments.

Physicochemical Characteristics (%m/m)			Ingredients
	SG1F	SG1S	SC	ST	FP
Moisture content	62.94	7.87	8.07	5.44	3.26
Protein content	11.74	38.50	34.72	38.42	55.21
Ash content	1.64	4.50	4.65	5.93	6.47
Lipid content	4.71	12.90	12.69	13.13	11.93
Carbohydrate content	18.97	36.23	39.87	37.08	23.13

SG1F: Freshly germinated soybeans, one day post-germination; SG1S: dried germinated soybeans, one day post-germination; SC: raw soybeans; ST: roasted soybeans.

. The recorded values range from 5.44% (ST) to 62.94% (SG1F) for moisture content; 11.74% (SG1F) to 38.50% (SG1S) for protein content; 1.64% (SG5F) to 5.93% (ST) for ash content; 4.71% (SG1F) to 13.13% (ST) for lipid content; and 18.97% (SG1F) to 39.87% (SC) for carbohydrate content.

3.2. Aflatoxin Levels in Treated Soybean Samples

Aflatoxin levels in treated soybean samples were below the European Union’s maximum permissible limit of 4 µg/kg [21]. The highest value was recorded for SG1S (2.30 µg/kg), while SG1F exhibited the lowest (0.00 µg/kg) (

Table 6. Total aflatoxin quantification.

Sample Type	Results (µg/kg)
ST	1.6
SC	1.66
SG1S	2.30
SG1F	0.00

SG1F: Freshly germinated soybeans, one day post-germination; SG1S: dried germinated soybeans, one day post-germination; SC: raw soybeans; ST: roasted soybeans.

).

3.3. Physico-Chemical Parameters of Water

Table 7. Average values of water physico-chemical parameters.

Diets	Parameters
	T °C	O2 (mg/L)	pH	Salinity (mg/L)
SG1F	29.44 ± 0.80 a	1.13 ± 0.38 a	7.91 ± 1.67 a	0.31 ± 0.03 a
SG1S	29.26 ± 0.79 a	1.34 ± 0.79 a	7.97 ± 1.28 a	0.31 ± 0.03 a
SC	29.15 ± 0.74 a	1.17 ± 0.45 a	7.92 ± 1.04 a	0.31 ± 0.03 a
ST	29.16 ± 0.81 a	1.38 ± 0.57 a	8.61 ± 1.98 a	0.32 ± 0.04 a

SG1F: Diet containing fresh one-day germinated soybean; SG1S: diet containing dried one-day germinated soybean; SC: diet containing raw soybean; ST: diet containing roasted soybean; T °C: temperature; O₂: dissolved oxygen; pH: hydrogen potential; Salinity: water salinity. The values in the table are expressed as means ± standard deviation; (a) statistically identical.

summarizes the average values of water’s physico-chemical parameters, including temperature, dissolved oxygen, pH, and salinity, across the different diets. Analysis of variance indicated no significant differences (p ≤ 0.05) in the effect of these diets on the evaluated parameters. All values fell within the optimal range for tilapia farming, except for dissolved oxygen levels.

3.4. Growth Performance of Fingerlings by Diet

Figure 3 illustrates the growth performance of fish across the experimental period (from day 0 to day 56) under the various dietary treatments. The Figure shows that fingerlings exhibited growth under all treatments during each monitoring session. However, the highest growth was observed with the control feed (ST), followed by SC, SG1S, and SG1F. Variance analysis revealed a statistically significant difference (p ≤ 0.05) among the dietary treatments.

3.5. Growth Parameters

Table 8. Mean values of growth parameters for different dietary treatments.

Diets		Parameters
	WG (g)	SGR (%/d)	DGR (g/d)
SG1F	16.07 ± 5.55 c	1.54 ± 0.45 d	0.29 ± 0.1 c
SG1S	16.30 ± 9.92 c	1.64 ± 0.52 c	0.29 ± 0.2 c
SC	18.93 ± 8.67 b	1.74 ± 0.49 b	0.34 ± 0.2 b
ST	23.40 ± 10.21 a	2.01 ± 0.50 a	0.42 ± 0.2 a

SG1F: Diet incorporating freshly germinated soybeans (one day); SG1S: diet incorporating dried germinated soybeans (one day); SC: diet incorporating raw soybeans; ST: diet incorporating roasted soybeans; WG: weight gain; SGR: specific growth rate; DGR: daily growth rate. Values are expressed as mean ± standard deviation; (a, b, c, d) statistically different.

presents the mean values of growth parameters (WG, SGR, and FCR) for the different diets. Variance analysis revealed a significant effect (p ≤ 0.05) of the diets on the growth parameters. Specifically, Duncan’s test indicated that the ST diet had a greater impact on WG, SGR, and FCR than the other diets. Conversely, SG1F exhibited the lowest values, indicating a less positive impact on growth parameters compared to the others. The effects of SG1F and SG1S diets were statistically identical for WG and FCR.

3.6. Feed Utilization Parameters

Figure 4 illustrates feed consumption across dietary treatments during the experimental period. At Day 14 (J14), feed intake was similar across all treatments. By Day 28 (J28), a slight increase in feed intake was observed for all diets. However, at Days 42 (J42) and 56 (J56), a decrease in feed consumption occurred, which was not correlated with prior intake levels. Notably, the analysis of variance revealed no significant differences between the treatments.

The feed conversion ratio (FCR) and feed efficiency rate (FER) are presented in

Table 9. Mean values of feed utilization parameters.

Diets	Parameters
	FCR	FER (%)
SG1F	3.87 ± 2.28 b	0.31 ± 0.11 c
SG1S	3.18 ± 2.90 b	0.30 ± 0.19 c
SC	2.75 ± 1.67 a	0.37 ± 0.17 b
ST	2.17 ± 1.80 a	0.41 ± 0.18 a

SG1F: Diet incorporating fresh one-day germinated soybeans; SG1S: diet incorporating dried one-day germinated soybeans; SC: diet incorporating raw soybeans; ST: diet incorporating roasted soybeans; FCR: feed conversion ratio; FER: feed efficiency rate. Values are expressed as means ± standard deviation; (a, b, c) statistically different.

. Analysis of variance revealed a significant effect (p ≤ 0.05) of the dietary treatments on feed utilization parameters, which ranged from 3.87 ± 2.28 (SG1F) to 2.17 ± 1.80 (ST) for FCR, and from 0.30 ± 0.19% (SG1S) to 0.41 ± 0.18% (ST) for FER. According to Duncan’s test, ST had a greater impact on both FCR and FER compared to the other diets (SC, SG1S, SG1F). Conversely, SG1F and SG1S exhibited less pronounced effects on feed utilization parameters (FCR and FER).

The FCR values for ST and SC were statistically similar, as were those for SG1F and SG1S. Similarly, for FER, the effects of SG1F and SG1S were also statistically comparable.

3.7. Survival Rate

The survival rate of fish fed the various diets after the experimental period ranged from 80% to 100%, varying by treatment (

Table 10. Survival rate of fish fed the various diets after 56 days.

Diets	Survival Rate (%)
SG1F	100
SG1S	88
SC	90.67
ST	89.33

SG1F: Diet incorporating fresh one-day germinated soybeans; SG1S: diet incorporating dried one-day germinated soybeans; SC: diet incorporating raw soybeans; ST: diet incorporating roasted soybeans.

). Specifically, the survival rate was 100% for SG1F, followed by 90.67% for SC, 89.33% for ST, and 88% for SG1S.

4. Discussion

The environmental conditions under which the fish were raised were consistent across all diets. In all experimental tanks, the values of the water’s physicochemical parameters remained within the optimal range, except for dissolved oxygen levels [22,23,24]. The low dissolved oxygen levels observed can be attributed to the groundwater source used, combined with the absence of artificial aeration devices in the tanks. Nevertheless, these oxygen levels were not influenced by the type of diet. Thus, the fish were exposed to the same environmental conditions, and the differences in their growth performance cannot be attributed to the rearing environment.

Chemical composition analysis revealed that SG1S was richer in protein, followed by ST and SC. The lower protein levels in fresh samples may be explained by the high water content, which acts as a dilution factor. Dormancy breaking during germination affects the chemical composition of seeds by activating existing enzymes and synthesizing new ones, such as proteases for proteins, lipases for lipids, and amylases for starch [25,26]. These enzymatic activities likely increased the protein, lipid, and carbohydrate content in SG1S. Rapid drying halts enzymatic processes by swiftly removing water, resulting in a higher concentration of proteins in roasted and dried soybean samples.

In contrast to chemical composition, SG1F exhibited lower aflatoxin levels than SG1S, SC, and ST. This difference may be linked to storage or preservation conditions. According to Ahmed et al. [27], storing seeds with moisture content above 10% promotes mold proliferation.

Statistical analyses of feed utilization parameters revealed no significant differences among diets. Thus, at a 5% error margin, it can be concluded that the fish consumed the diets similarly without showing dietary preference.

Regarding feed utilization indices (FCR and FER), the results showed that ST exhibited the best performance (lowest FCR and highest FER), followed by SC, SG1S, and SG1F. These differences are due to the distinct physicochemical characteristics of the soybean treatments.

Growth performance results indicated that the reference diet ST had the best performance, followed by SC, SG1S, and SG1F. Variance analysis revealed a significant effect on weight gain at a 5% threshold (p < 0.05), with ST being significantly superior to other treatments (SC, SG1S, SG1F). Similar trends were observed for weight gain (WG), specific growth rate (SGR), and daily growth rate (DGR), which may be attributed to its higher organic content, including protein (38.42%), lipids (13.13%), and carbohydrates (37.08%).

The weight gain range observed in this study surpassed that reported by Boma et al. [10] at the same station using blood meal as a protein source over 42 days of feeding, but was lower than the results of Kirimi et al. [28] in Kenya, who used blood meal over a 100-day feeding period. The specific growth rate (SGR) obtained in this study was lower than that of Dibala et al. [24] in Burkina Faso, who used plant-based proteins over 56 days of rearing in plastic tanks, but higher than the results of Boma et al. [10]. The daily growth rate (DGR) was lower than those reported by Dibala et al. [24].

This study highlights the superiority of the roasted soybean (ST) diet compared to the SG1S diet, despite their theoretically comparable protein levels. Furthermore, our findings indicate that the aflatoxin content in SG1S meals was relatively high compared to ST. Numerous studies have demonstrated the detrimental effects of aflatoxins on fish growth [14,29]. This study suggests that optimal preservation of SG1S meals could minimize these factors, improving fish growth when fed this diet.

The survival rates observed during the experiment were high, ranging between 80% and 100%. This indicates that soybeans, in the forms used for this study’s formulations, were non-toxic to fish. The high survival rate of fish fed raw soybean (90.67%), second only to SG1F (100%), demonstrates that incorporating raw soybeans at 30% is not toxic to Nile tilapia. However, our survival rate results exceeded those of Bamba et al. [30] in Côte d’Ivoire, who reported survival rates between 75% and 95%, but were slightly lower than those of Boma et al. [10], who reported rates between 96.67% and 100% for a study conducted at the same station in Agbodrafo.

5. Conclusions

The primary objective of this study was to evaluate the growth performance of Nile tilapia juveniles (Oreochromis niloticus) fed diets incorporating soybeans (roasted or germinated). The study concluded that the water’s physicochemical parameters, such as temperature, pH, and salinity, remained within optimal ranges for Nile tilapia farming, resulting in high survival rates across the experimental diets. Among the diets tested, the best growth performance was observed with the reference diet (roasted soybeans), followed in descending order by raw soybeans, one-day dried germinated soybeans, and fresh one-day germinated soybeans. A similar trend was noted for feed utilization indices (FCR and FER). Daily growth rates showed a consistent upward trend for all diets from the start to the end of the experiment.