Effect of replacing solvent extracted soybean meal with extruded expeller soybean meal on growth performance of Japanese quail

Introduction

Protein nutrition has gained increased global attention in recent years, with poultry meat and eggs recognized as economical and clean protein sources. Among poultry species, quail meat is considered for its delicacy, offering higher protein, lower fat and calorie content, and greater concentrations of essential vitamins (A, C, B-complex) and minerals (Ca, Fe, P, K, Zn, Cu) compared to chicken and duck meat (Quaresma et al., 2022) [1] . Optimal quail production depends heavily on high-quality protein and energy sources with a balanced amino acid profile. Soybean meal (SBM) remains the most widely used plant protein source in poultry diets because of its high crude protein content, complementary amino acid profile and superior amino acid digestibility (Ravindran et al., 2013) [10] . Conventional solvent-extracted soybean meal (SESBM), produced using solvents such as n-hexane or acetone, contains less than 1-1.5% residual oil following the removal of nearly 95% of the bean oil. Although solvent extraction partially reduces antinutritional factors like trypsin inhibitors, the low residual oil content necessitates the addition of external fat sources to meet metabolizable energy requirements. Recent advances in processing have led to the development of extruded-expelled soybean meal (EESBM), produced through high-temperature (≈135 °C), short-time (≈30 s), highpressure extrusion followed by mechanical expelling (Nelson et al., 1987; Newkirk, 2010). Mechanical extraction removes approximately 70% of the oil, yielding a meal with 6.5-10% residual oil. The heat generated during extrusion effectively inactivates antinutritional factors, reduces trypsin inhibitor activity, enhances protein denaturation and increases enzymatic accessibility, thereby improving nitrogen digestibility. The higher residual oil also contributes to increased digestible and metabolizable energy compared to SESBM. Additionally, extrusion improves starch gelatinization, ingredient sterilization and overall feed efficiency in poultry. Hence this research study was conducted to assess the growth performance of feeding EESBM in Japanese quails.

Materials and Methods

A four-week biological trial was conducted using 180-day old Japanese quail chicks, which were individually weighed and divided into three treatment groups (T 1 , T 2 and T 3 ) with three replicates each and 20 chicks per replicate. The experimental birds were reared under cage system and each replicate was housed separately. The replacement levels of SESBM with EESBM in the formulated diet of Japanese quail was given in the Table 1. The composition of the starter and finisher diets were presented in the Table 2 andTable 3, respectively. All the diets were formulated on isocaloric and iso-nitrogenous basis. The experimental birds were fed with starter diet for first 2 weeks and finisher feed (3 to 4 weeks age). All the birds were allowed ad libitum access to drinking water throughout experiment with nipple drinkers. The experiment lasted for 28 days. The birds were weighed at the end of each week. The feed intake was determined by calculating the difference between the feed offered and the residual feed in each replicate of every treatment group. The feed conversion ratio (FCR) was computed accordingly. Mortality if any also recorded during the entire period of study. The cost of production was also calculated at the end of the study. All statistical analyses were carried out using SPSS version 25. For data exhibiting a normal distribution, one-way analysis of variance (ANOVA) was applied, and differences among treatment means were determined using Duncan's multiple range test.

Results and Discussion

The effects of replacing Solvent Extracted Soybean Meal (SESBM) with Extruded Expeller Soybean Meal (EESBM) at different levels on the growth performance and economics of Japanese quail is presented in Table 4. A significant improvement in body weight was observed from the second week onwards in quails fed diets containing 50% (T 2 ) and 100% (T 3 ) EESBM compared with the control (p<0.05). By the fourth week, the highest body weight was recorded in T 2 (191.9 g), which was 6.1% higher than the control (180.88 g). Although T 3 (187.55 g) also showed improvement, it was less than T 2 , indicating that increasing EESBM inclusion from 50% to 100% did not produce a linear enhancement in growth. The body weight gain also followed a similar trend, with T 2 showing the highest overall gain (183.12 g), significantly higher than the control (172.1 g) (p<0.05); whereas, T 3 (178.84 g) showed intermediate weight gain and statistically comparable performance. The superior performance at 50% EESBM might be attributed to improved nutrient digestibility and reduced anti-nutritional factors resulting from extrusion and expeller processing. Extrusion has been shown to increase protein availability, improve amino acid digestibility and reduce trypsin inhibitors in soybean products (Ravindran, 2013; El-Sayed, 2013) [10,4] . Previous studies in broilers and quail have similarly reported improved growth when processed soybean meals were included at moderate levels (Karr-Lilienthal, 2004; Kansal et al., 2023) [6,5] . However, the slight decline in T 3 performance suggested that excessive replacement might reduce palatability or cause amino acid imbalance, which has been previously documented in birds fed high levels of heat-processed soybean meals (Nourmohammadi and Khosravinia, 2015; Li et al., 2021) [8,7] . The feed intake was increased from the third week onwards in birds fed 50% EESBM (112.09 g/week). The total feed intake over the experimental period was highest in T 2 (419.07 g), which was 2.71% higher than the control (408 g). Interestingly, the 100% EESBM group (T 3 ) consumed slightly less feed (404.5 g) than the control, although differences among treatments were not statistically significant. The improved feed intake in T 2 might be linked to the enhanced palatability and textural quality of extruded feed. Extrusion improved the aroma, reduced bitter components and enhanced voluntary intake in poultry (Serrano et al., 2013; Choct, 2017) [12,3] . The lower feed intake observed in T 3 indicated the reduced palatability at higher processed soybean levels, consistent with previous findings in Japanese quail and broilers (Nourmohammadi and Khosravinia, 2015) [8] . The feed conversion ratio showed significant variation among treatments from the fourth week onward (p<0.05). The overall FCR was lowest in T 3 (2.26), followed by T 2 (2.29), both of which performed better than the control group (2.37). The improved FCR in EESBM-fed birds could be attributed to enhanced starch gelatinization, increased protein digestibility and structural modification of feed particles during extrusion (Abdollahi et al., 2018; Svihus, 2014) [2,13] . Earlier studies on processed soybean meals in quail and broilers have reported similar improvements in feed efficiency (Sarıçiçek et al., 2005; Ojediran et al., 2020) [11, 9] . The mortality remained low across all treatments. T 1 and T 3 recorded the lowest mortality (1.7%), while T 2 had a slightly higher value (3.3%). As no pathological or clinical abnormalities were detected, the variation is likely due to environmental influence or incidental and unrelated to diet. The economic assessment of the study presented in Table 4 indicated a significant increase in feed cost per bird in T 2 (₹16.75) and T 3 (₹16.80) compared with the control (₹16.20) (p<0.05). The higher cost might correspond to the relatively higher price of EESBM. Despite this, profit per bird did not vary significantly among the treatments: T 1 -₹22.5, T 2 -₹20.7 and T 3 -₹22.5. This suggested that the improved growth performance especially the better FCR in T 2 and T 3 offsets the increased feed cost. Similar findings were reported in economic analyses of quail and broilers fed processed soybean meals or value-added protein sources (Ojediran et al., 2020; Kansal et al., 2023) [9,5] .

Conclusion

The present study demonstrated that partial replacement of SESBM with EESBM at 50% in the diet could offer optimal improvements in growth performance, weight gain, feed intake and FCR in Japanese quail. Although, 100% replacement improved FCR, it did not contribute to superior body weight compared with 50% replacement. These outcomes aligned with the previous literatures indicating that moderate levels of processed soybean meal enhance nutrient utilization and performance in monogastric species, whereas excessive inclusion may compromise palatability or nutrient balance.

References

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