Special Issue:

Advancements in Animal Health and Production in Low and Middle-Income Countries

Effects of Dietary Soybean Bioactive Peptides on Egg Quality Parameters in Laying Japanese Quail

Ahmed A.D. Al- Doori*, Asaad D.S. Al-Doori, Saif A.J. Aldarraji, Ahmed A. Allaw, Haitham R.M. Al-Kaisi

Department of Animal Production, College of Agriculture, Tikrit University, Tikrit, Iraq.

Received | July 01, 2025; Accepted | August 20, 2025; Published | August 30, 2025

*Correspondence | Ahmed A.D. Al- Doori, Department of Animal Production, College of Agriculture, Tikrit University, Tikrit, Iraq; Email: [email protected]

Citation | Al-Doori AAD, Al-Doori ADS, Aldarraji SAJ, Allaw AA, Al-Kaisi HRM (2025). Effects of dietary soybean bioactive peptides on egg quality parameters in laying Japanese quail. J. Anim. Health Prod. 13(s1): 202-207.

DOI | https://dx.doi.org/10.17582/journal.jahp/2025/13.s1.202.207

ISSN (Online) | 2308-2801

Copyright: 2025 by the authors. Licensee ResearchersLinks Ltd, England, UK.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

INTRODUCTION

Quails are characterized by their early growth, short generation times, and short incubation periods compared to other domesticated animal species. These features make them an essential source of animal protein, such as meat and eggs, in a short period (Lukanov and Pavlova, 2020; Al-Hindawi et al., 2021; Ismail et al., 2024). Domestic birds are considered an animal model and occupy an important place in experimental research (Morris et al., 2020).

SBP They are an excellent food source because they contain dietary fiber, high-quality protein, a high percentage of unsaturated fatty acids, and other substances that have various physiological effects (Omoni and Aluko, 2005; Kogut et al., 2013; Udenigwe, 2014; Mohsen et al., 2024).

Soybeans are a rich source of plant proteins and phytochemicals, such as isoflavones and phenolic compounds, due to their rich amino acid composition, high content, and low price, making them the second largest source of vegetable oils globally (Singh and Hati, 2014; Lule et al., 2015). Based on the dry weight of their seeds, the composition of soybeans consists of protein (30–35%), fat (20%), dietary fiber (9%), and moisture (8.5%) (Li et al., 2021).

They are considered functional foods, as they help prevent and treat various diseases while providing good nutrition. Experimental studies have demonstrated their role in enhancing blood circulation, regulating digestion, and promoting bowel movements. In addition, they contain phytochemicals known for their positive effects on health, such as fibre, isoflavones, phospholipids, saponins, phenolic acids, trypsin inhibitors, and phytic acid (Kogut et al., 2013; Udenigwe, 2014; Wei et al., 2024). Proteins are an important nutrient in chicken eggs. These proteins are characterized by a high rate of digestion and absorption, and they release complete proteins (Puglisi and Fernandez, 2022). Research studies have identified 371, 428, and more than 500 protein types in egg white, yolk, and cortical membrane proteins, respectively, through proteomic analyses (Kulshreshtha et al., 2022; Sarantidi et al., 2023). White proteins primarily include albumin, ovotransferrin, ovomucin, ovomucoid, and lysozyme (Kulshreshtha et al., 2022). Yolk proteins primarily include lipofetellin, globular protein, phosvitin, and low-density lipoprotein (LDL) (Marcet et al., 2022). Egg shell membrane proteins mainly contain collagen, keratin, agrin, and laminin (Makkar et al., 2015). Egg proteins exhibit various functional activities, including antibacterial, immune-enhancing, and antioxidant properties (Liu et al., 2015; Pimchan et al., 2023).

The study aimed to incorporate plant-based bioactive soybean peptides, which provide essential amino acids, into the bird’s diet, potentially influencing the chemical composition and quality of the egg fat and improving its overall quality.

MATERIALS AND METHODS

This study was conducted in the poultry farm of the College of Agriculture, Tikrit University. Ninety-six eight-week-old female brown quails were used in this study. They were randomly distributed into four treatments, with each treatment comprising 24 birds and eight replicates. SBP compounds were added as follows: The first treatment (T1) was the control treatment without any additives. The additional treatments included three levels (1, 2, and 3 g/kg) feed for the second, third, and fourth treatments, respectively.

Bird management

The production ration prepared by the Feed Laboratory of the Animal Field Department at Tikrit University was used to feed the birds. This ration contained 2,800 kcal/kg of feed and a protein content of 21%. Feed and water were freely available to the birds. SBP were hand-mixed for manual addition to the treatment rations.

Sample collection and characteristics

After the female Japanese quail reached 50% of her egg production, 100 eggs were taken within one week of each treatment. The eggs were cracked, and measurements were made to evaluate egg quality. Egg weight in grams and albumin and yolk quality were measured individually using a sensitive three-stage balance after separation. After cracking the eggs on a flat glass surface, the albumin height and diameter (in mm) were measured using an electronic Vernier scale, dye unit, and pH meter. Yolk quality was determined by measuring yolk weight, height (mm), diameter, and pH. Albumin and bile index were measured in dye units. Cholesterol concentration was measured according to the method of Elias and Francy (1968), and triglyceride concentration was measured according to the method of Kaya et al. (2001) using the following equations.

Albumin index = Albumin height (mm) / Albumin diameter (mm)

Yolk index = yolk height (mm) / yolk diameter (mm)

Haugh unit = 100 Log (H+7.57-1.7W0.37), H= height albumin mm, w= egg weight, 7.57= constant number

Egg yolk cholesterol (mg/g yolk) = sample reading/standard cholesterol reading x 2

mm: means millimeter

Haugh unit = 100 Log (H+7.57-1.7W0.37), H= height albumin mm, w= egg weight, 7.57= constant number

Soybean peptides used in the study

SBP was obtained from Vanavaran Novin Gostar Biotechnology Co., Tehran, Iran (as yellow-brown powder). The molecular weight distribution of SBP was determined using a Superdex HR 10/300 GL peptide column connected to an HPLC system (Karimzadeh et al., 2016).

Statistical analysis

Data were analyzed using a completely randomized design to determine the effect of the treatment ratios used on the studied traits. Significant differences between mean values were compared using Duncan’s multiple range test (Duncan, 1955) at a significance level (p ≤ 0.05), using SAS (2012) The following mathematical model worked:

Yij = μ + Ti + Eij

Where; Yij = the observed value specified for treatment I; μ = the mean year of the studied recipe; Ti = the behavioral effect i; eij = the random experimental error, which is normally distributed with a mean equal to zero and a variance of σ2.

 

Table 1: Effect of adding SBP to quail diets on egg weight, albumin content, Hugh unit, albumin weight, and pH of eggs (Mean ± Standard error).

Traits treatments	Egg weight (g)	Albumen height (mm)	Haugh units	Albumen weight (g)	Albumen pH
T1	10.14±0.005 c	3.96±0.005 b	87.65±0.02 b	6.03±0.008	9.31±0.58
T2	10.17±0.005 c	3.98±0.005 b	87.73±0.02 b	6.37±0.02	9.02±0.57
T3	11.59±0.33 b	4.37±0.32 b	88.77±1.92 b	6.45±0.33	9.05±0.58
T4	12.46±0.34 a	5.12±0.005 a	92.25±0.20 a	6.16±0.008	9.09±0.58
Significance	*	*	*	N.S	N.S

 

The letters a, b, c, and d within one column indicate statistically significant differences at the probability level (P ≤ 0.05). N.S.: means no significant differences at (P˃0.05). * Indicates the presence of significant differences (P ≤0.05). T1 Control, T2 1 gm/kg of SBP, T3 2 gm/kg of (SBP), T4 3 gm/kg of SBP.

 

Table 2: Effect of adding SBP to quail diets on yolk weight, height, diameter, index, and pH of eggs (Mean ± Standard error).

Traits treatments	Yolk weight (g)	Yolk height (mm)	Yolk diameter (mm)	Yolk index (%)	Yolk pH
T1	2.83±0.02 b	9.72±0.005 d	24.62±0.005 a	0.39±0.003 b	6.40±0.58
T2	2.64±0.04 b	9.82±0.005 c	24.32±0.34 ab	0.40±0.006 ab	6.17±0.58
T3	2.94±0.15 b	9.85±0.005 b	24.33±0.33 ab	0.40±0.006 ab	6.13±0.58
T4	3.42±0.21 a	9.90±0.008 a	23.72±0.008 b	0.42±0.001 a	6.10±0.57
Significance	*	*	*	*	N.S

 

The letters a, b, c, and d within one column indicate statistically significant differences at the probability level (P ≤ 0.05). N.S.: means no significant differences at (P˃0.05). * Indicates the presence of significant differences (P ≤0.05). T1 Control, T2 1 gm/kg of SBP, T3 2 gm/kg of (SBP), T4 3 gm/kg of SBP.

 

RESULTS

Effect of adding SBP to quail diets on egg weight, albumin content, Haugh unit, albumin weight, and albumin pH

The results of Table 1 showed a significant increase (P ≤ 0.05) in egg weight for the third and fourth treatments compared to the first and second treatments, while the results of the same Table 1 indicated a significant increase for the fourth treatment compared to the three experimental treatments in albumin height and Haugh unit, respectively. The results also showed no significant differences between the experimental treatments for both albumin weight and pH value.

Effect of adding SBP to quail diets on yolk weight, height, diameter, yolk index, and yolk pH

From the results of the statistical analysis in Table 2, we find a significant increase (P ≤ 0.05) in favor of the fourth addition treatment compared to the rest of the experimental treatments in yolk weight. At the same time, we note that there is a significant increase for the addition treatments compared to the control treatment in yolk height. The results also indicated a significant decrease in yolk diameter for the fourth treatment compared to the first treatment. The results of the Table 2 also showed a significant increase for the fourth treatment compared to the control treatment in yolk index, and we did not notice any significant differences between the experimental treatments in yolk pH.

The effect of adding SBP to quail diets on cholesterol and triglycerides in the yolk

The results of the statistical analysis, presented in Table 3, showed a significant decrease (P ≤ 0.05) in cholesterol levels between the third and fourth addition treatments compared to the first and second treatments. The results of the Table 3 also showed a significant decrease in triglycerides in the addition treatments compared to the control treatment.

 

Table 3: The effect of adding SBP to quail diets on cholesterol and triglycerides in the yolk (Mean±Standard error).

Trait treatments	Triglycerides (mg/100ml)	Cholesterol (mg/100ml)
T1	20.99±0.30 a	12.35±0.005 b
T2	20.36±0.18 b	12.45±0.005 a
T3	18.65±0.008 d	10.12±0.005 d
T4	19.34±0.008 c	10.22±0.005 c
Significance	*	*

 

The letters a, b, c, and d within one column indicate statistically significant differences at the probability level (P ≤ 0.05). N.S.: means no significant differences at (P ˃ 0.05). * Indicates the presence of significant differences (P ≤ 0.05). T1 Control, T2 1 gm/kg of SBP, T3 2 gm/kg of (SBP), T4 3 gm/kg of SBP.

 

DISCUSSION

The reason for the increase in egg weight in the treatments where bioactive soybean peptides were added in the third and fourth treatments may be due to the role of peptides in the development of intestinal villi, increasing their ability to be absorbed in the intestine, increasing the stability of intestinal bacteria, and providing crude protein and fat in the feed, thus improving the digestibility of food, which contributes to improved egg production and weight gain. The reason for the increase in albumin and Haugh unit in the fourth addition treatment may be attributed to the fact that peptides have antioxidant properties that protect proteins and reduce the breakdown of albumin proteins due to oxidative stress, especially in the summer. Previous studies have indicated that the addition of SBP leads to an improvement in Haugh unit because the peptides work to maintain albumin weight by reducing moisture loss and retaining water within the egg albumin, thereby reducing water evaporation through the eggshell pores. In addition, they enhance the thickness of the albumin layers, as the peptides support the formation of albumin proteins such as ovalbumin and maintain the structural integrity, which increases albumin weight and reduces the decrease in its height during storage. On the other hand, peptides work to prevent the oxidative breakdown of proteins. These peptides contain compounds such as isoflavones and sulfur-containing amino acids, including methionine, which prevent the oxidation of albumin proteins, thereby preserving their structural integrity and weight. They also work to reduce protein degradation during long-term storage. Albumin proteins are susceptible to degradation by enzymes or heat, and peptides help inhibit these processes, thereby preserving the overall mass of albumin.

Preserving yolk quality may be attributed to the fact that peptides inhibit the oxidation of lipids in the yolk, thereby increasing the shelf life of eggs and reducing rancidity, especially in eggs stored for extended periods. On the other hand, peptides protect chicken liver cells (where yolk proteins such as vitellogenin are produced), which enhances the formation of egg yolk. These peptides offer health benefits for poultry, as they function as a prebiotic that supports the growth of beneficial bacteria in the intestine, thereby improving the overall absorption of nutrients. They also play a role in reducing oxidative stress in birds, which has a positive impact on egg quality and production. Among their physical properties is the ability to increase the consistency and moisture of the yolk, which reduces its tendency to dry out during storage. The decrease in the diameter of the yolk in the fourth treatment indicates the strength of the yolk membrane. The lower the quality of this membrane, the more susceptible the yolk becomes to damage. The strength of the yolk membrane is an important characteristic, especially in the food industry when separating albumin from the yolk, because it helps prevent the yolk part from mixing with the albumin part during separation. This is what Olukosi et al. (2018) found when adding biologically active soybean peptides to chicken feed: It improved the color and yolk index. However, the diameter of the yolk decreased significantly for the eggs collected after feeding the peptides for eight weeks.

According to Table 3, the decrease in triglyceride and cholesterol values may be due to the effect of peptides that lower LDL cholesterol and raise HDL cholesterol. These varying effects of peptides may be related to lipid metabolism and the presence of secondary metabolites, such as the concentration of essential amino acids, as well as the size and type of peptides produced (Tang et al., 2012). The decrease in triglyceride and total cholesterol in egg yolk is due to soybean peptides lowering their levels in blood serum (Alahyaribeik et al., 2022).

CONCLUSIONS

We conclude from this study that soybean peptides improved egg quality traits: Egg weight, albumin content, Haugh unit, yolk weight, yolk height, yolk diameter, yolk index, and reduced yolk triglycerides and cholesterol. Therefore, peptides may play a role in producing healthier eggs for consumers.

RECOMMENDATIONS

We recommend adding 3g/kg of SBP to improve egg quality, reduce harmful cholesterol and triglyceride levels, and encourage consumers with atherosclerosis and hyperlipidemia to use levels higher than 3g/kg.

ACKNOWLEDGMENTS

We appreciate and thank the technicians for their effective contribution to the field experiment and laboratory tests.

New statements

By using SBP, intestinal health and digestive enzyme activity can be improved, thereby improving egg quality.

AUTHOR’S CONTRIBUTION

Ahmed A.D. AL-Doori: Initiated the idea for the submitted research project, contributed to sample collection and laboratory testing, and contributed to the preparation of the final version of the manuscript. Asaad D. S. AL-Doori: Supervised the formulation of the bird feed and the addition of (BSP), conducted statistical analysis of the data, and interpreted the results. Saif A. J. aldarraji: Verified the data analysis and contributed to supervising and guiding the technicians in the field. Ahmed A. Allaw: Initiated the idea for the submitted research project and reviewed the final version of the manuscript. Haitham R. M. Al-Kaisi: Data Analysis

Generative AI or AI-assisted Technology Statement

The author(s) declare that no Genrative AI was used in the creation of this manuscript.

Conflict of interest

The authors have declared no conflict of interest.

REFerences

Al-Hindawi, A., AlDallal, U., Waly, Y. M., Hussain, M. H., Shelig, M., Saleh ElMitwalli, O. S. M. M., Henari, F. Z. (2021). An exploration of nanoparticle-based diagnostic approaches for coronaviruses: SARS-CoV-2, SARS-CoV and MERS-CoV. Nanomaterials, 12(20), 3550. https://doi.org/10.3390/nano12203550

Alahyaribeik, S., Nazarpour, M., Tabandeh, F., Honarbakhsh, S., and Sharifi, S. D. (2022). Effects of bioactive peptides derived from feather keratin on plasma cholesterol level, lipid oxidation of meat, and performance of broiler chicks. Tropical Animal Health and Production, 54(5), 271. https://doi.org/10.1007/s11250-022-03244-1

Duncan DB (1955). Multiple rang and multiple F-test. Biometrics, 11: 4-42. https://doi.org/10.2307/3001478

El-Hindawy MM, Alagawany M, Mohamed LA, Soomro J, Ayasan T (2021). Influence of dietary protein levels and some cold pressed oil supplementations on productive and reproductive performance and egg quality of laying Japanese quail. J. Hellenic Vet. Med. Soc., 72(3): 3185-3194. https://doi.org/10.12681/jhvms.28513

Elias, A. and Franey , R.J.(1968). Serum cholesterol measurement based on ethanol extraction and ferric chloride-sulfuric acid. Journal Chimica Acta, 21:255-293. https://doi.org/10.1016/0009-8981(68)90135-6

Ismail, U. M., Vohra, M. S., Onaizi, S. A. (2024). Adsorptive removal of heavy metals from aqueous solutions: Progress of adsorbents development and their effectiveness. Environmental Research, 251, 118562. https://doi.org/10.1016/j.envres.2024.118562

Karimzadeh S, Rezaei M, Yansari AT (2016). Effects of canola bioactive peptides on performance, digestive enzyme activities, nutrient digestibility, intestinal morphology and gut microflora in broiler chickens.

Kaya, S., Keçeci, T. and Haliloglu, S.(2001). Effects of zinc and vitamin A supplements on plasma levels of thyroid hormones, cholesterol, glucose and egg yolk cholesterol of laying hens. Research in Veterinary Science,71: 135–139.https://doi.org/10.1053/rvsc.2001.0500

Kogut MH, Genovese KJ, He H, Swaggerty CL, Jiang Y (2013). Modulation of chicken intestinal immune gene expression by small cationic peptides as feed additives during the first week posthatch. Clin. Vaccine Immunol., 20(9): 1440-1448. https://doi.org/10.1128/CVI.00322-13

Kulshreshtha G, Diep T, Hudson HA, Hincke MT (2022). High value applications and current commercial market for eggshell membranes and derived bioactives. Food Chem., 382: 132270. https://doi.org/10.1016/j.foodchem.2022.132270

Li Y, Liu Y, Wu J, Chen Q, Zhou Q, Wu F, Che L (2021). Comparative effects of enzymatic soybean, fish meal and milk powder in diets on growth performance, immunological parameters, SCFAs production and gut microbiome of weaned piglets. J. Anim. Sci. Biotechnol., 12: 1-11. https://doi.org/10.1186/s40104-021-00625-8

Liu J, Jin Y, Lin S, Jones GS, Chen F (2015). Purification and identification of novel antioxidant peptides from egg white protein and their antioxidant activities. Food Chem., 175: 258-266. https://doi.org/10.1016/j.foodchem.2014.11.142

Lukanov, H., Pavlova, I. (2020). Domestication changes in Japanese quail (Coturnix japonica): a review. World’s Poultry Science Journal, 76(4), 787-801. https://doi.org/10.1080/00439339.2020.1823303

Lule VK, Garg S, Pophaly SD, Hitesh, Tomar SK (2015). Potential health benefits of lunasin: A multifaceted soy-derived bioactive peptide. J. Food Sci., 80(3): R485-R494. https://doi.org/10.1111/1750-3841.12786

Makkar S, Liyanage R, Kannan L, Packialakshmi B, Lay Jr JO, Rath NC (2015). Chicken egg shell membrane associated proteins and peptides. J. Agric. Food Chem., 63(44): 9888-9898. https://doi.org/10.1021/acs.jafc.5b04266

Marcet I, Sáez-Orviz S, Rendueles M, Díaz M (2022). Egg yolk granules and phosvitin. Recent advances in food technology and applications. Lwt, 153: 112442. https://doi.org/10.1016/j.lwt.2021.112442

Mohsen AK, Jassim SE, Alaridhi TT, Al-Erjan AM, Lahhob QR, Mudhafar M (2024). Revolutionizing infectious disease management in animals through advanced phage therapy: A comprehensive strategy for the eradication of multidrug-resistant bacterial pathogens. J. Anim. Health Prod., 12(s1): 157-167. https://doi.org/10.17582/journal.jahp/2024/12.s1.157.167

Morris, S. E., Moment, A., Thomas, J. D. (2020). Caring for bereaved family members during the COVID-19 pandemic: before and after the death of a patient. Journal of pain and symptom management, 60(2), e70-e74. https://doi.org/10.1016/j.jpainsymman.2020.05.002

Olukosi OA, Xiao W, Jia J (2018). Peptide supplementation to nutrient-adequate diets enhanced internal egg quality during storage in hens at peak production. J. Sci. Food Agric., 98(5): 1850-1855. https://doi.org/10.1002/jsfa.8661

Omoni AO, Aluko RE (2005). Soybean foods and their benefits: Potential mechanisms of action. Nutr. Rev., 63(8): 272-283. https://doi.org/10.1301/nr.2005.aug.272-283

Pimchan T, Tian F, Thumanu K, Rodtong S, Yongsawatdigul J (2023). Isolation, identification, and mode of action of antibacterial peptides derived from egg yolk hydrolysate. Poult. Sci., 102(7): 102695. https://doi.org/10.1016/j.psj.2023.102695

Puglisi MJ, Fernandez ML (2022). The health benefits of egg protein. Nutrients, 14(14): 2904. https://doi.org/10.3390/nu14142904

Sarantidi E, Ainatzoglou A, Papadimitriou C, Stamoula E, Maghiorou K, Miflidi A, Anagnostopoulos AK (2023). Egg white and yolk protein atlas: New protein insights of a global landmark food. Foods, 12(18): 3470. https://doi.org/10.3390/foods12183470

SAS (2012). Statistical analysis system, user’s guide. Statistical. Version 9.1th ed. SAS. Inst. Inc. Cary. N.C. USA.

Singh BP, Vij S, Hati S (2014). Functional significance of bioactive peptides derived from soybean. Peptides, 54: 171-179. https://doi.org/10.1016/j.peptides.2014.01.022

Tang JW, Sun H, Yao XH, Wu YF, Wang X, Feng J (2012). Effects of replacement of soybean meal by fermented cottonseed meal on growth performance, serum biochemical parameters and immune function of yellow-feathered broilers. Asian-Austral. J. Anim. Sci., 25(3): 393. https://doi.org/10.5713/ajas.2011.11381

Udenigwe CC (2014). Bioinformatics approaches, prospects and challenges of food bioactive peptide research. Trends Food Sci. Technol., 36(2): 137-143. https://doi.org/10.1016/j.tifs.2014.02.004

Wei Y, Zhao X, Xu T, Liu Z, Zuo Y, Zhang M, Yin H (2024). Soybean bioactive peptide supplementation affects the intestinal immune antioxidant function, microbial diversity, and reproductive organ development in roosters. Animals, 14(13): 1954. https://doi.org/10.3390/ani14131954