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. 2025 Sep 3;104(11):105771. doi: 10.1016/j.psj.2025.105771

Worldwide researches on broiler breeders: A 25-year bibliometric review

Omid Bouzari 1, Mahdi Zhandi 1,⁎, Sayyed Mohammad Hadi Hussaini 1
PMCID: PMC12455124  PMID: 40930000

Abstract

The poultry industry plays a key role in meeting global protein needs amid changing demographics and lifestyles, and is constantly growing and evolving. Genetic selection and optimization of broiler breeder flocks have been key drivers of growth, making the maintenance of their health and performance essential both for chick production and for the long-term sustainability of the industry. Despite the high importance of broiler breeder flocks, no systematic bibliometric study has yet been conducted that specifically focuses on research in this area. To address this gap, we analyzed global research trends in broiler breeding science from 2000 to mid-2025 using bibliometric methods, based on 2,209 publications from the Scopus database. Scientific publications on broiler breeders have more than tripled over the past quarter-century compared to the previous five decades, maintaining an annual growth rate of approximately 4 %. These publications received an average of 17.06 citations per article, with approximately 21 % representing collaborative efforts between international research teams. The United States and China dominate in publications volume, although they show relatively low levels of international research collaboration. Conversely, countries such as the United Kingdom and Belgium, while contributing fewer total number of publications, show higher citation impact and broader international collaboration networks. The findings from co-word and co-citation analysis highlight several emerging research directions that emphasize interdisciplinary approaches involving nutrition, reproduction, welfare, and technological advancement. Ultimately, through this data analysis, we hope that our findings will help advance broiler breeding toward greater productivity, sustainability, and animal welfare.

Keywords: Bibliometric analysis, Co-word analysis, Co-citation analysis, International collaboration, Poultry

Introduction

The world population is substantially increasing and it is anticipated to reach 10.3 billion people in mid-2080 (United Nations, 2024). The increase in world population is a reason for an increase in food demand which consequently exerts a tremendous pressure on the world food systems especially in terms of protein supply. In the last decades, the poultry industry has been known as one of the fastest growing sectors of the global food and meat industry. According to published statistics, global production of poultry meat reached 150 million tons in 2024 which approximately includes 40 % of the total meat production, and it maintained its position as the most produced meat, globally. Moreover, the 2.6 % growth in poultry meat production in 2024 compared to 2023 represents the crucial role of poultry industry in the world's food security and economic development (FAO, 2025). Therefore, the poultry industry plays a key role in meeting the global demand for protein amid demographic changes and shifting lifestyles (Mottet and Tempio, 2017). Among the principal factors contributing to the growth of the poultry industry are genetic selection and optimization of broiler breeder flocks. Over the past six decades, intensive genetic selection aiming at achieving rapid growth and improved feed conversion ratio has caused a significant change in the poultry industry (Hartcher and Lum, 2020). Still, the mentioned substantial improvement in the poultry industry comes with enormous challenges, especially in the research area (Bist et al., 2024). Challenges such as fertility reduction and issues related to health and welfare are the results of intensive growth in poultry production (Cash et al., 2025; Zuidhof et al., 2015). Accordingly, maintaining the health and performance of broiler breeder flocks is of high importance, not only for chick production but also for long-term stability of the poultry industry. Despite the importance of breeding and management of broiler breeder flocks, no systematic bibliometric study has yet been conducted on articles related to broiler breeders. One of the main challenges in the mentioned area is that a major part of the research and innovations related to the broiler breeders is conducted and kept within the commercial breeding companies and remains unpublished due to confidentiality and competition with other companies (Burnside and Neeteson, 2025; Tallentire et al., 2016). The limitation in accessibility to the findings from commercial companies has led to a small number of peer-reviewed scientific articles, which in turn has considerably increased the requirements for analytical research. Therefore, presenting a bibliometric review of existing research is a valuable tool for identification of the trends, gaps and future research priorities in the broiler breeders research area, which lacks transparency in many aspects. Bibliometric analysis, a quantitative method for investigation of global volume of publications, citation networks and subject trends in a scientific field can provide a clear perspective on the evolutionary path of a research field over time. Risk management in broiler farms, technology application, heat stress management and antibiotic alternatives have been the focus of previous bibliometric studies in the field of poultry science (Oliveira et al., 2023; Sharif et al., 2023; Wu et al., 2022). However, there is a lack of comprehensive bibliometric studies focusing on research conducted on broiler breeders over the past 25 years (from 2000 to 2025).

Accordingly, using the bibliometric techniques and analysis of Scopus database, the present study aims to achieve the following objectives: (1) Investigating the annual trend in scientific production, (2) Identifying the authors, institutions and countries with the highest publications in the mentioned field, (3) Analysis of co-word and co-citation networks, and (4) Investigating the evolutionary process of fundamental subjects within the field of broiler breeder flocks.

Based on the objectives outlined above and to further clarify the topic being talked about, this study seeks to answer the following research questions:

  • 1.

    what is the current status of scientific publications on broiler breeder flocks?

  • 2.

    how are papers related to broiler breeder flocks cited in the scientific literature?

  • 3.

    which subjects associated with broiler breeder flocks have gained notable attention?

  • 4.

    What patterns of author collaboration and participation are observed in papers related to broiler breeder flocks?

Methodology

Bibliometric approach

A three-step approach, including bibliometric, co-word, and co-citation analysis was applied to answer the research questions. Bibliometric analysis provides a quantitative assessment of published research and, through bibliometric mapping, reveals the intellectual structure of a field by organizing documents, authors, and keywords (Donthu et al., 2021). In addition, Complementary approaches such as co-word (Kostoff, 1993) and co-citation (Small, 1973) analyses enrich this perspective by identifying emerging themes, influential contributions, and conceptual linkages.

Data collection

The data were obtained from Scopus database and the search focused on the “Topic” section, which includes titles, abstracts, and keywords of the published documents. Two keywords were identified through brainstorming and comprehensive literature review. With regard to the lack of available documents in this field and to make the current study more comprehensive, only two keywords were selected encompass all existing research in this field. The Boolean operator “OR” was applied in keyword combinations. The search was confined to papers published between 01 January 2000 and 30 April 2025 and all other documents were omitted. To maintain language consistency, only papers written in English were considered (Table 1).

Table 1.

Research screening protocol.

Search string TITLE-ABS-KEY ("broiler breed*" OR "broiler parent*")
Subject areas "Agricultural and Biological Sciences", "Veterinary", "Immunology and Microbiology", and "Biochemistry, Genetics and Molecular Biology"
Document type Journal articles in English
Period 1 January 2000–30 April 2025
Database Scopus
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The asterisk (*) attaches to the stem of a word and searches for any word which includes that stem, or the letters before the asterisk.

Screening process

In the current study, Preferred Reporting Items For Systematic Review And Meta-Analysis framework was applied for screening (Fig. 1) (Moher et al., 2015; Page et al., 2021). The strict screening process resulted in selection of 2209 documents eligible for bibliometric analysis. The data collection and screening process are presented in detail in Table 2 and Fig. 1, respectively.

Fig. 1.

Fig 1

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Document selection protocol based on the PRISMA approach.

Table 2.

Overall information on the bibliometric analysis.

Overall data Value
Documents 2209
Journals (Sources) 333
Author's keywords 4158
Indexed keywords 5919
Average citations per document 17.06
Authors 6482
Documents per author 0.341
Authors per document 2.935
Co-Authors per document 5.15
Document Average Age 10.6
International co-authorships % 21.32
Annual Growth Rate %1 −0.89
Years 2000-2025
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1

Note: The negative value includes 2025 (incomplete year); when excluding 2025, the rate is +3.99 %.

Data analysis

The data analysis process included three main steps. In the first step, the descriptive statistics were obtained from the Scopus database using Rstudio software version 2025.05.0 + 496 and the Bibliometrix package version 5.0.0, and then analyzed (Aria and Cuccurullo, 2017). The most important extracted statistical indexes were as follows: annual scientific production, annual growth rate, authors’ international collaboration, prolific authors, leading journals, and top countries in terms of documents and citations. Also, to analyze international collaboration, the numbers of single country publications (SCP) and multiple country publications (MCP) were calculated for each country. The data were extracted using authors’ affiliation information (AU_CO) and the Bibliometrix package in R software. For better accuracy, the duplicate entries for countries in each paper were removed before calculation. Finally, the ratio of MCP to the total number of papers for each country was calculated as an indicator of the level of the international collaboration. In the second step, co-word and co-citation analysis were conducted using VOSviewer software version 1.6.20 (van Eck and Waltman, 2010).

Co-word analysis

Co-word analysis (keyword co-occurrence analysis) was conducted to investigate the conceptual structure and research trends in this field. In this study, co-word analysis was performed on author’s keywords extracted from the Scopus database using the full counting method, and the correlations between keywords were assessed based on the number of documents that shared keywords in common. Among the 4158 primary keywords, those appeared at least nine times were selected, and unrelated keywords were removed. This threshold was chosen after testing lower and higher cut-off points, as it produced a manageable network size while retaining the most representative keywords, following standard practice in bibliometric studies (van Eck and Waltman, 2010). The analysis resulted in a network map comprising 127 keywords, which were grouped into five distinct research clusters.

Co-citation analysis

In the current study, co-citation analysis was performed on the references cited in papers available in the Scopus database. In this phase, the full counting method was also applied to assign equal weight to each co-citation. The relationship between the references was calculated based on the number of documents sharing citations in common. Among the 66379 cited references, those cited at least nine times were selected. This threshold was chosen after testing several cut-off points, as it provided a manageable network size (100 cited references) while ensuring that the most influential works were retained (van Eck and Waltman, 2010). The resulting network map included 100 cited references, grouped into four research clusters.

Results and discussion

Bibliometric analysis

This analysis sheds light on the importance of research in the field of broiler breeders. The findings suggest that research in the field of broiler breeders has generally been increasing during the last 25 years; however, some fluctuations are observed in the meantime. The information presented in Fig. 2 and Table 2 confirms the claim. This trend has substantial implications for researchers and stakeholders in this field. Over the past two decades, several substantial fluctuations in the number of published papers in the field of broiler breeders have been observed. The most notable declines observed in the research trend can be grouped into two major periods: the early 2000s (2001-2003) and the mid-2000s (2006-2008). In the initial phase following 11 September attacks, much of the research funding in the US (e.g., USDA grants) was redirected to the fields such as biosecurity and counter-bioterrorism (Council, 2007), which consequently resulted in investment reduction in agricultural research. Also, other countries have reported similar priorities in research funding. In the second period, the H5N1 avian influenza outbreak began and governments, particularly in the US and EU, focused on controlling it by allocating special funds, which consequently led to reduced funding in other research areas (Schnirring, 2006). Additionally, the global financial crisis of 2008 had a significant negative impact on research investments and caused a noticeable decline in governments’ support for agricultural research across many countries (Guesmi and Gil, 2017; Heisey and Fuglie, 2018).

Fig. 2.

Fig 2

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Average monthly publications covering the research field in different years.

In the current bibliometric study, a comprehensive collection of 2209 documents from 333 different sources (journals) were analyzed. It is noteworthy that the documents were published by 6482 researchers over a 25-year period (from 2000 to 2025). On average, each document received 17.06 citations. Descriptive statistics suggest that each researcher has published an average of 0.341 papers, and an average of 5.15 authors per paper was recorded. Also, it is noteworthy that approximately 21.32 % of these papers were written with international collaborations, indicating a moderate level of international collaborations in this field.

The annual growth rate of papers related to broiler breeders is −0.89 % over the review period; however, when excluding the year 2025 (since 2025 is still ongoing), the growth rate increases to 3.99 %. The growth rate exhibits a linear trend, reflecting the growing and sustained significance of this research field in the current decade. Specifically, as it is presented in Fig. 3, from the beginning of 2000 to 30 April 2025, a total of 2243 documents have been published in this field, of which 2,209 were included after screening and removing irrelevant records. This number is approximately 3.2 times (229.3 %) higher than the total number of publications in this domain from the earliest available data in the Scopus database (1965) up to the beginning of 2000 (681 documents). This trend indicates a significant leap in research activity related to broiler breeders over the past 25 years.

Fig. 3.

Fig 3

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Annual trend in the number of publications covering the research field.

The document average age index, which refers to the average age of scientific documents, indicates how much time has passed since the cited papers were originally published (published documents in a specific field). The value of this index is 10.6 years in the field of broiler breeders, suggesting that many of cited papers are relatively old. Although this trend highlights the existence of old and important scientific foundations in this field, it also reflects a slow pace in updating scientific research and emphasizes the need for more recent studies.

The results of this bibliometric analysis clearly illustrate the increasing trend of interest and significance in broiler breeder research. Table 3 presents the top 10 authors in this field along with their h-index value, ranked by the number of published papers. The H-index is a metric which strikes a balance between the number of published papers and their citations and is a valid criterion for assessing a researcher’s impact (Hirsch and Buela-Casal, 2014).

Table 3.

Top 10 most productive authors based on the number of published documents.

Authors Affiliation Total publications H-index
Zuidhof, M.J. University of Alberta (Canada) 51 30
Wilson, J.L. University of Georgia (United States) 47 26
Gous, R.M.. University of KwaZulu—Natal (South Africa) 46 31
Brake, J. NC State University (United States) 39 39
Zaghari, M. University of Tehran (Iran) 37 24
Robinson, F.E. University of Alberta (Canada) 37 32
Coon, C. N. University of Arkansas (United States) 35 31
Renema, R.A. University of Alberta (Canada) 33 26
Decuypere, E. KU Leuven (Belgium) 32 66
Zhandi, M. University of Tehran (Iran) 29 27
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The geographical distribution of published papers in this field (Table 4) indicates that authors affiliated with universities in the United States made the greatest contribution. This pattern aligns with the position of the United States as one of the major producers and exporters of chicken meat, as well as their targeted attempts to develop this sector (FAO, 2025). China ranks second in this field, with a number of published papers approximately half that of the United States. Iran, Brazil and Canada are among the most active countries in this field.

Table 4.

Top 10 most productive countries based on the total number of published documents.

Country No. documents Total citations Average document citation MCP ratio
United states 296 6686 22.60 25.3 %
China 217 2820 13.00 19.8 %
Iran 189 2059 10.90 14.8 %
Brazil 148 1896 12.80 19.6 %
Canada 140 3033 21.70 22.1 %
United Kingdom 92 3063 33.30 37.0 %
Turkey 78 992 12.70 12.8 %
Netherlands 62 1392 22.50 19.4 %
Georgia 56 863 15.40 5.4 %
India 47 481 10.20 0 %
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However, impact and quality evaluation of the papers are not limited to the number of papers. Although researchers of Finland universities and institutes have published fewer papers (64 papers), they received the highest average document citation (64.00) among the countries surveyed. Following Finland researchers, researchers from the Slovakia (52.50) and the Belgium (40.90) have played a prominent role in broiler breeders research, recording a substantial citation index. This pattern highlights the global nature of research in this field and reflects the collaborative attempts of researchers from different countries to advance knowledge and innovation in broiler breeder research.

Fig. 4 investigates international collaboration patterns in the field of broiler breeders. This diagram represents the number of single country publications (SCP) and multiple country publications (MCP) based on the corresponding authors country. Although US and China possess the highest level of scientific production, they surprisingly have relatively low rates of international collaboration. A major part of the papers published in these countries are written by local researchers. Although some countries, such as the UK, have published fewer papers, they exhibit a higher rate of international publications, approximately half of their publications have been co-authored with researchers from other countries. By expanding global collaborations and applying the knowledge and expertise of international researchers, the global scientific community can accelerate the progress, promote innovation and offer comprehensive solutions to improve the performance and productivity of broiler breeders globally (Bist et al., 2024).

Fig. 4.

Fig 4

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Research international collaboration patterns based on the corresponding author’s country.

Table 5 provides information on the top 10 journals that have published the most analytical papers. The top three journals publishing the most papers in this field are Poultry Science (523 papers), British Poultry Science (115 papers), and Avian Diseases (103 papers), respectively. The highest number of citations was also recorded for the aforementioned journals. Interestingly, although journals such as Avian Pathology and Journal of Applied Poultry Research have published fewer papers compared to the aforementioned journals, they have recorded substantial citation counts which indicates the high impact of papers published in these journals. Table 5 also presents data related to journal quality, including publisher, citation index, ranking, and impact factor. All journals were ranked within the Q1 to Q3 in the Scimago Journals Ranking, with an exception for International Journal of Poultry Science, which is not indexed in any of the quartile ranking databases.

Table 5.

Top 10 leading journals based on the total number of published documents.

Journals Publisher No. documents Citations Best rank Impact Factor
Poultry Science Elsevier 523 12613 Q1 3.8
British Poultry Science Taylor & Francis 115 2597 Q2 1.6
Avian Diseases American Association of Avian Pathologists (AAAP) 103 2476 Q2 1.3
Journal of Applied Poultry Research Elsevier 103 1601 Q2 1.6
International Journal of Poultry Science Asian Network for Scientific Information 77 762 - 0.6
Avian Pathology Taylor & Francis 64 2088 Q1 2.5
Brazilian Journal of Poultry Science Fundacao APINCO de Ciencia e Tecnologia Avicolas 56 538 Q3 1.1
Applied Animal Behaviour Science Elsevier 35 617 Q1 2.2
Animals MDPI 33 251 Q1 2.7
Animal Elsevier 23 311 Q1 4.0
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Co-word analysis

This analysis has addressed the identification of dominant subjects and emerging trends in the field of broiler breeders. In this study, 127 authors keywords were extracted from the analyzed documents using network analysis. These keywords were analyzed in terms of frequency and used to develop a network model.

According to Table 6, which presents the top 10 keywords, the term “broiler breeder” was the most frequently used, with 382 occurrences. Additionally, some other keywords, such as 'broiler', are sometimes used in the literature to indirectly refer to broiler breeders. On the other hand, the presence of keywords such as “hatchability” and “fertility” among the most frequently used terms highlights the vital role of reproduction and physiology in the field of broiler breeders. Reproduction and physiology in broiler breeders play a critical role in the productivity and sustainability of poultry industry. Improving reproductive performance, including increased fertility and hatchability, depends directly on the physiological health and appropriate management of broiler breeder flocks (Teofilo et al., 2023).

Table 6.

Top 10 most frequent Author's keywords among analyzed documents.

Author's keywords No. occurrences/frequency
Broiler breeder 382
Broiler 203
Hatchability 130
Chicken 112
Poultry 102
Fertility 94
Egg production 78
Performance 72
Incubation 57
Body weight 44
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Fig. 5 presents a network visualization of keyword co-occurrence in papers published during the first 25 years of the current century (2000 to 2025). This visualization highlights the top keywords listed in Table 6. The Occurrence metric refers to the number of times a keyword appears across different papers, while the Link Value indicates the number of connections that keyword has with other terms. The Link Strength Values represents the total connection strength of a specific keyword (van Eck and Waltman, 2010).

Fig. 5.

Fig 5

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Network visualization of keyword co-occurrence analysis.

Table 7 summarizes the identified clusters, their respective subjects and the most frequent keywords within each cluster.

Table 7.

Most frequent keywords based on keyword co-occurrence analysis.

Cluster Theme Most Frequent Keywords
1 (Red) Nutritional Modulation and Performance performance; broiler breeder hen; embryo; immunity; broiler chicken; selenium; in ovo injection; reproductive performance; growth performance; zinc; egg; vitamin e; progeny; meat quality; hatching; offspring; antioxidant status; oxidative stress; nutrition; immune response; amino acid; broiler breeding; probiotics; protein; 25-hydroxycholecalciferol; eggshell quality; production performance; in ovo feeding; in ovo; phytase; manganese; energy; vitamin c; lysine
2 (Green) Reproductive Physiology and Welfare broiler breeder; broiler; egg production; body weight; feed restriction; reproduction; welfare; heat stress; growth; mortality; animal welfare; behavior; gene expression; body composition; stress; sexual maturity; microbiota; ascites; hen; liver; hunger; ovary; photoperiod; production; feed intake; feed efficiency; corticosterone; carcass composition; testis; testosterone; breeder hen; qualitative feed restriction; cold stress
3 (Blue) Infectious Diseases and Diagnostic Approaches chicken; poultry; salmonella; elisa; escherichia coli; epidemiology; vaccine; campylobacter; antimicrobial resistance; vaccination; pcr; mycoplasma gallisepticum; mycoplasma synoviae; seroprevalence; phylogenetic analysis; colibacillosis; prevalence; ornithobacterium rhinotracheale; salmonella enteritidis; antibiotic resistance; pathology; hatchery; fowl adenovirus; avian influenza; apec; isolation; pathogenicity; infectious bronchitis virus; inclusion body hepatitis
4 (Yellow) Embryonic Development and Hatchability Factors hatchability; egg quality; chick quality; chick weight; hatching eggs; incubation; embryonic mortality; embryonic development; embryo mortality; broiler performance; egg weight; temperature; broiler breeder age; breeder age; egg storage; flock age; docosahexaenoic acid
5 (Purple) Male Fertility and Reproductive Traits sperm; semen; fertility; sperm quality; antioxidant; artificial insemination; aging; semen quality; rooster; breeder; layer; cryopreservation; sperm quality index; age
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The network analysis includes five distinct clusters, with the following specific focuses:

1. Nutritional modulation and performance improvement (red cluster)

This cluster includes studies addressing the complex challenges related to nutritional modulation and performance improvement in broiler breeder flocks (34 papers). Terms such as “performance”, “protein”, and “energy” indicate research efforts to ensure nutritional modulation and performance improvement.

2. Reproductive physiology and welfare (green cluster)

This cluster includes studies on reproductive physiology and welfare in broiler breeders (33 papers). Terms such as “reproduction”, “sexual maturity”, “ovary”, and “testis” emphasize physiological aspects. Additionally, keywords such as “welfare”, “stress”, and “behavior” are associated with broiler breeders’ welfare. To optimize reproductive performance and improve poultry health, it is necessary to understand the endocrine of avian reproduction and implementing welfare-enhancing strategies—including environmental enrichment and behavioral monitoring—are essential for optimizing reproductive performance and improving poultry health (Ottinger and Bakst, 1995).

3. Infectious diseases and diagnostic approaches (blue cluster)

This cluster includes studies focused on identifying infectious diseases, as well as improving and optimizing diagnostic methods (29 papers). Keywords such as “salmonella”, “epidemiology”, “vaccine”, and “Escherichia coli” highlights the infectious diseases and diagnostic approaches aspects. Effective management of infectious diseases requires a comprehensive diagnostic approach to allow for a rapid and accurate disease detection, as well as preventive interventions (Liebhart et al., 2023).

4. Embryonic development and hatchability factors (yellow cluster)

This cluster investigates the different stages of embryonic development and hatchability factors (17 papers). Keywords such as “embryonic mortality” and “embryonic development” are associated with embryonic growth. Also, keywords such as “hatchability”, “temperature”, “hatching eggs”, and “egg quality” are commonly applied in relation to hatchability. Strict control of incubation condition including temperature, humidity, ventilation, and egg turning ensures proper embryonic development and significantly increases the hatchability rate and post hatch quality of chickens (Tona et al., 2022).

5. Male fertility and reproductive traits (purple cluster)

This cluster includes research related to male fertility and their reproductive characteristics (14 papers). Keywords such as “sperm”, “semen”, and “fertility” are related to male fertility and reproductive characteristics. Roosters’ sperm quality indices including semen volume, sperm concentration, and progressive motility are used as factors determining their fertility. Improving aforementioned indices through nutritional modulation can improve the reproductive efficiency of broiler breeder roosters (Fouad et al., 2020).

Emerging trends

The overlay visualization in Fig. 6 shows that keywords such as “cryopreservation”, “egg storage”, “antimicrobial resistance”, “microbiota”, “sperm quality”, “chick quality”, and “embryo mortality” have appeared more frequently in recent studies. The emerging trends align with previous research and have been developed through a focus on new technologies, quality optimization, and addressing current challenges. Additionally, a comparison between the Fig. 5, Fig. 6 indicates that the yellow and purple clusters contain more emerging keywords compared to the other clusters. This indicates a strong and structured connection between emerging trends and earlier research. Emerging trends are typically established on the foundation of previous concepts and findings, and are advanced through new instruments and approaches.

Fig. 6.

Fig 6

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Overlay visualization of keyword co-occurrence analysis.

Co-citation analysis

This analysis investigates the relationships between the topics and concepts within the field of broiler breeders. To conduct this analysis, a set of 100 publications (reference) was extracted from the reference list of the analyzed documents. This collection was analyzed to assess the number of co-citations and to create a network model. Table 8 presents the top 10 references with the highest co-citation frequency, based on Total Link Strength. These references have the highest cross-citation frequency compared to others and demonstrate their effectiveness and their fundamental role in developing the research topic thus far. Analysis of the titles in Table 8 suggests that all of the highly cited papers are related to broiler breeders, particularly in the areas of nutrition and flock performance.

Table 8.

Top 10 co-cited references based on their total link strength.

No. Documents Citation Total link strength Link Cluster No.
1 De Jong, et al. (2002). Effects of restricted feeding on physiological stress parameters in growing broiler breeders. British Poultry Science, 43(2), 157–168. 24 155 48 3
2 Zuidhof, (2018). Lifetime productivity of conventionally and precision-fed broiler breeders. Poultry science, 97(11), 3921-3937. 20 149 48 2
3 Van der Klein, et al. (2018). The effect of rearing photoperiod on broiler breeder reproductive performance depended on body weight. Poultry Science, 97(9), 3286-3294. 15 127 46 2
4 Hocking, et al. (2001). Welfare assessment of modified rearing programmes for broiler breeders. British Poultry Science, 42(4), 424–432. 18 119 44 3
5 Renema, et al. (2007). Reproductive efficiency and metabolism of female broiler breeders as affected by genotype, feed allocation, and age at photostimulation. 2. Sexual maturation. Poultry Science, 86(10), 2267-2277. 17 117 45 2
6 Zuidhof, et al. (2014). Growth, efficiency, and yield of commercial broilers from 1957, 1978, and 2005. Poultry science, 93(12), 2970-2982. 23 114 49 2
7 Van Emous, et al. (2015). Effects of growth patterns and dietary protein levels during rearing of broiler breeders on fertility, hatchability, embryonic mortality, and offspring performance. Poultry Science, 94(4), 681-691. 17 103 45 2
8 Van der Klein, et al. (2018). Early photostimulation at the recommended body weight reduced broiler breeder performance. Poultry Science, 97(10), 3736-3745. 11 103 43 2
9 Van Emous, et al. (2013). Effects of growth patterns and dietary crude protein levels during rearing on body composition and performance in broiler breeder females during the rearing and laying period. Poultry Science, 92(8), 2091-2100. 12 102 45 2
10 Zuidhof, et al. (2015). Effects of broiler breeder management on pullet body weight and carcass uniformity. Poultry science, 94(6), 1389-1397. 18 98 53 3
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Fig. 7 presents a network visualization of co-citation relationships between the analyzed references. The top 10 highly cited references identified in Table 8 are clearly observable in this figure and confirm their central position and their effectiveness within the reviewed scientific system. The identified clusters in this figure present groups of publications with a common conceptual focus and thematic connection. Color coded nodes illustrate the thematic connection between the references within each cluster.

Fig. 7.

Fig 7

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Network visualization of co-citation analysis.

Co-citation analysis includes four clusters:

Cluster 1 (red): Nutritional strategies and growth performance

This cluster comprises 32 references. In the cluster of nutritional strategies and growth performance, studies focus on the precise formulation of feed ingredients and the application of bioactive supplements to improve growth and feed efficiency. For instance, the application of probiotics, prebiotics, antioxidants and organic acids in the diet not only improves daily growth and feed conversion ratio, but also enhances gut health and meat texture quality (Choi et al., 2023). Additionally, recent studies have shown that postbiotic additives significantly improve the growth indices and the immune status of poultry by modulating the gut microbiota and increasing mucus production (Urban et al., 2024).

Cluster 2 (green): Physiology and performance optimization in modern poultry breeding

This cluster comprises 31 references and emphasizes a better understanding of physiologic processes and precise technologies to optimize poultry performance. Studies on innovative approaches, including the control and measurement of biosensors, real-time monitoring systems, and computer modeling tools, have shown that parameters such as temperature, humidity, light, and nutritional patterns can be adjusted to minimize stress and improve feed conversion efficiency in the flock (Brassó et al., 2025). Additionally, application of metabolic models and simulations of poultry responses to feed and light manipulation enable the prediction of growth outcomes and supports more informed decision-making in management practices (Leishman et al., 2023).

Cluster 3 (blue): Welfare, behavior and management practices

This cluster consists of 20 references. The welfare, behavior and management approaches cluster focus on applying ethology and automated technology-based methods to monitor and improve welfare of poultry. The application of motion sensors, smart cameras, and computer vision algorithms enable early detection of pain and stress symptoms, allowing managers to implement timely interventions such as environmental enrichments and stocking density management (Li et al., 2020). In addition, studies on the effect of flock density on poultry social behavior have shown that reducing the number of chickens per square meter and providing an enriched environment enhance natural behaviors such as dustbathing and foraging, thereby improving the overall welfare of the flock (Evans et al., 2023).

Cluster 4 (yellow): Reproductive physiology and welfare-related management

This cluster includes 17 references and focuses on the physiological mechanisms regulating reproduction and their relationship with avian welfare. Smart regulation of photoperiod, light intensity and spectrum, along with nutritional manipulation promotes a better balance between growth and reproductive performance. Optimizing photoperiods and micronutrient composition can increase fertile egg quality and egg production (Scanes et al., 2020). Future oriented research suggest that genetic selection aimed at decoupling ovary growth factors from general body growth rate can enhance the reproductive performance of broiler breeders without compromising their welfare (Bazer et al., 2019).

Conclusions and future research directions

This study explains the significance of the broiler breeders over the past 25 years through bibliometric analysis. The results show that the published documents related to broiler breeders from 2000 to mid-2025 was 3.2 times greater than the entire scientific output in this field during the preceding five decades. Moreover, the annual growth rate of approximately 4 % highlights the dynamic development of this research field over the past quarter-century.

The average citation count of papers reflects the significant impact and relative maturity of this research area. Furthermore, the level of international collaboration indicates that the potential for cross-border cooperation is moderately high, though improvements can be made in expanding international networks. Meanwhile, countries such as China, Iran, and India —major producers of poultry and eggs—play a vital role in expanding the international network. The volume of scientific output from these countries in this field is considerable; although their efforts are primarily concentrated at the fundamental research level.

On the other hand, developed countries such as the UK and the USA are capable of conducting advanced and interdisciplinary research at the frontiers of knowledge by addressing the fundamental challenges. This claim is supported by the high average citation counts and the strong international scientific collaboration reflected in the research output of these countries.

By aggregating the results of word clustering (Table 7) and co-citation clustering (Table 9), five key research directions within this research domain:

  • •

    Balancing diet and production performance: Concepts such as in ovo feeding, antioxidants, probiotic supplements, and energy regulation.

  • •

    Reproductive physiology and performance optimization: Exploring the effect of genetics, photo stimulation, growth patterns, and precision feeding on fertility and performance.

  • •

    Animal welfare and poultry management: Evaluation of behavioral parameters, stress levels, and feed restriction as well as the design of welfare improvement programs.

  • •

    Embryonic development and factors affecting hatchability: The impact of egg age, incubation condition, antioxidants, and eggs quality on hatch rate and embryonic health.

  • •

    Male fertility and reproductive traits: Evaluation of sperm quality, cryopreservation techniques, sperm biological indicators, and reproductive consequences.

Table 9.

Representative publications for clusters based on co-citation analysis.

Cluster Cluster lable Number of ducuments Representative publications
1 (Red) Nutritional Strategies and Growth Performance 32 NRCCouncil et al. (1994); AOACAssociation of Official Analytical (1995); Leeson and Summers (2001); Bowmaker and Gous (1991); Kidd (2003); Tona et al. (2003); Wilson (1997); (Roque and Soares, 1994)
2 (Green) Physiology and Performance Optimization in Modern Poultry Breeding 31 Bornstein et al. (1984); Decuypere and Bruggeman (2007); Zuidhof et al. (2014); Renema et al. (2007); Hocking, Maxwell, et al. (2002); de Beer and Coon (2007); Joseph et al. (2000); van Emous et al. (2015); Lewis et al. (2003)
3 (Blue) Welfare, Behavior, and Management Practices 20 De Jong et al. (2002); Hocking et al. (2004); Savory et al. (1993); Sandilands et al. (2006); Mench (2002); Zuidhof et al. (2017); Nielsen et al. (2011); Bruggeman et al. (1999); de los Mozos et al. (2017); Hocking et al. (1996)
4 (Yellow) Reproductive Physiology and Welfare-Related Management 17 Hocking (2004); Hocking (1993a); Hocking, Bernard, et al. (2002); Spratt and Leeson (1987); CCAC (2009); Savory et al. (1996); Hocking et al. (1987); Hocking (1993b)
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These axes are highly dependent on each other. These synergistic interactions can result in significant advances in both research development and performances within this research area.

Suggestions for future research

Based on the aforementioned key areas, the following research directions are proposed:

Application of omics approaches (e.g., genomics, proteomics) to better understand of biological mechanisms within each cluster.

Conducting comparative studies and highlighting genetic variations among different lines to optimize nutrition and reproduction.

Research on the egg and chick microbiome and its effect on embryonic health and post-hatch performance.

Development of specific testing protocols for precision feeding technologies using sensor systems and data mining to reduce wastes and enhance production efficiency.

Integrating measurable welfare indicators, (e.g., corticosterone levels, stress-related behaviors) into poultry rearing protocols to enhance the welfare standards.

Long-term studies investigating the effect of environmental stressors (e.g., heat, high stocking density) on reproduction and embryonic quality.

Limitations

This study was conducted solely using the Scopus database. While utilizing multiple databases can enhance comprehensiveness, a focus on a single database can reduce redundancy and conflicting data. In the current study, only scientific papers published in English were analyzed, while other documents (such as conference proceedings, books, reports, new editions, etc.) were excluded to enhance consistency. The clustering results are influenced by software parameters, which can produce varying outcomes across different configurations. However, the authors have made substantial efforts to ensure the validity of the findings. Future studies should periodically update and review these findings to ensure compliance with the latest scientific advancements.

Disclosure instructions

During the preparation of this work, the authors used OpenAI's ChatGPT in order to make partial grammar and phrasing corrections. After using this tool/service, the authors reviewed and edited the content as needed and takes full responsibility for the content of the publication.

CRediT authorship contribution statement

Omid Bouzari: Writing – review & editing, Writing – original draft, Visualization, Validation, Software, Resources, Methodology, Formal analysis, Data curation, Conceptualization. Mahdi Zhandi: Writing – review & editing, Writing – original draft, Validation, Supervision, Resources, Project administration, Investigation, Conceptualization. Sayyed Mohammad Hadi Hussaini: Writing – review & editing, Writing – original draft, Validation, Resources, Investigation.

Disclosures

The authors declare that there is no conflict of interest regarding the publication of this article. The research was conducted independently, and no financial, personal, or institutional interests influenced the results or interpretation of the data.

Acknowledgements

The authors would like to express their sincere appreciation to Mr. Seyed Erfan Hosseini (ORCID: 4262-0339-0006-0009) for his valuable guidance in the preparation of the current manuscript.

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