The domestic animal has had a crucial impact on human history, societies, and civilizations (Hata et al., 2021; Diamond, 2002). Among domesticated animal species, the domestic chicken known scientifically as Gallus gallus domesticus stands out as the most widely distributed poultry globally (Miao et al., 2013; Zhang et al., 2017; Eda, 2021).
Chickens have played roles in societies for millennia, serving as a source of food, symbols of status and wealth, participants in religious rituals, and even engaging in activities like cockfighting for entertainment (Granevitze et al. 2009). The domesticated chicken’s versatility reflects the cultural diversity and historical evolution of human civilization across different regions (Crawford, 1984). From Asia to Africa, Europe to the Americas, chickens have left a lasting mark on cultures and traditions.
Genetic research and archaeological discoveries shed light on the process of chicken domestication and the genetic lineage of present-day chickens (Tixier Boichard et al. 2011; Storey et al., 2007). The Red Jungle Fowl, native to regions in southeastern Asia, is recognized as the ancestor of modern domestic chickens (Peters, 2016). Multiple domestication events occurred between the Pleistocene and Holocene eras, with chickens spreading across continents through human migration and trade routes (Mwacharo, 2013). The movement of the chickens across continents was made possible by interactions influencing biological and cultural landscapes. Chickens made their way to Europe through trading routes from both the south and north with traces of their presence found in civilizations like Egypt (Houlihan, 1986; Crawford, 1990). Additionally, analysis of DNA suggests that chickens spread from Southeast Asia to Oceania and the Americas; however, there is debate regarding their specific distribution in the Americas (Storey et al., 2007; Maio et al., 2013).
Furthermore, the domestication of chickens marked a significant transition in agricultural practices, with humans selectively breeding birds for desired traits such as meat and egg production, ornamental features, and uniformity (Elferink et al., 2012). These breeding efforts, dating back thousands of years, laid the foundation for today’s diverse chicken breeds and varieties used in commercial production (Núñez-León et al., 2019). Furthermore, chickens played crucial roles in early agricultural economies, providing not only sustenance but also contributing to economic activities through trade and commerce (West & Zhou, 1988).
Moreover, the legacy of chicken domestication reverberates in contemporary agricultural systems worldwide. The success of the poultry industry today, particularly focused on broiler production, can be credited to centuries of breeding and genetic advancements (FAO, 2020). The United States stands out as a leading source of chicken meat, showcasing the result of generations of advancements, in agriculture and industry as noted by the National Chicken Council in 2022. Similarly, countries across Asia have embraced chicken domestication, reflecting its enduring popularity and economic significance (Liu et al., 2006).
1.1.2 Modern Broiler Industry in USA
The poultry industry, in the United States and worldwide, has evolved changes over time evolving from small-scale, non-specialized operations to the highly integrated, specialized, and efficient industry it is today (Sainsbury, 2000; Muir and Aggrey, 2003; Schmidt et al., 2009; Paxton et al., 2010; Tallentire et al., 2016). In the 1900s, chicken production mainly involved small-scale units across the US and other regions (Sainsbury, 2000; Muir & Aggrey, 2003). However, by the 1930s and mid-1940s, there was a shift towards increased production driven by advancements in genetic improvement programs and advanced breeding techniques inspired by plant breeding methods (Sainsbury, 2000). This shift towards industrialization and specialization led to productivity with a 600% growth in broiler meat production in the US between 1968 and 2018 (USDA, 2019). This growth was fueled by the standardization of poultry practices and products through integrated production systems and technology transfer (Sainsbury, 2000; Bessei, 2018). The adoption of production models involving farmers also played a key role in driving industry expansion.
The development of poultry breeding technologies has been central to these transformations (Muir & Aggrey, 2003; Hunton, 2006; Albers, 1998). Throughout history, the breeding of poultry has evolved from mass selection techniques to utilizing technologies that manage reproduction, track pedigrees, and accurately determine true breeding values, thus transforming the breeding process (Muir & Aggrey, 2003). In broiler production, a common practice involves crossing breeding lines in three-way or four-way combinations over several generations to produce specialized commercial broilers with specific breeding objectives (Pollock, 1999; Paxton et al., 2010). The concept of a breeding pyramid in broiler production involves stages such as pure breeding lines, great grandparent stock, grandparent stock, parent stock, and ultimately the broilers themselves (Figure 3; Pollock, 1999; Muir & Aggrey, 2003). Leading breeding companies like Cobb Vantress and Aviagen play roles in providing material to the industry and influencing both the well-being and productivity of broiler chickens through selective breeding practices (EFSA, 2010). Furthermore, contemporary breeding programs have transitioned from focusing on weight through mass selection to considering multiple criteria related to growth characteristics that align with consumer preferences (Paxton et al., 2010). Advances in genetics have facilitated this shift, leading to significant enhancements in broiler growth rates and meat yield (Tallentire et al., 2016).
The progress can be seen in the increase in broiler growth rates and the reduction in the time it takes for broilers to reach market weight (HSUS, 2013; Zuidhof et al., 2014). Nowadays, broiler strains can achieve a weight of 2.6 kg in 6 weeks, an improvement compared to the 16 weeks it took in 1920. This swift advancement has resulted in over a 400% rise in growth rate between 1950 and 2005 along with a 50% decrease in feed conversion ratio (Figure 4; Zuidhof et al., 2014). Moreover, the environmental sustainability of broiler production has been enhanced as broilers now reach market weight in more than half the time, leading to reduced feed consumption and environmental impact (Tallentire et al., 2018). This has played a role in the US broiler industry’s ability to meet ever-growing demand for poultry products as consumers prefer broiler meat over other available proteins for its affordability, nutritional benefits, and versatility (Al Nasser et al., 2007).
The commercialization of the poultry industry began during the 1950s with a shift away from backyard farming practices. This change was fueled by an increasing demand for poultry products and advancements across areas, such as management techniques, automation technology, breeding programs, genetic selection, nutritional discoveries, and disease control efforts (Chambers et al., 1981). Since the commercialization of the chicken industry, the consumption of chicken per capita has boomed, with an increase from 30 pounds annually to around 110 pounds. While beef consumption has slightly decreased, pork and turkey consumption have remained steady (Meyer and Steiner, 2011) and in 2016 broilers, turkeys, chickens, and eggs contributed $38.7 billion to annual revenue (U.S. Poultry and Egg Association, 2016).
Techniques for improvement have been instrumental in enhancing traits like breast filet yield and feed conversion ratio (Albers, 1998; Havenstein et al., 2003). However, different growth rates have led to health challenges in broilers that affect industry profits (Julian, 2005; Julian, 1998). Despite obstacles faced by the industry, there is a growing demand for poultry products due to their value and affordability. Other contributing factors include increased awareness about health and no cultural or religious restrictions on poultry consumption (Tallentire et al., 2018).
To recap, today’s industrial broiler is the outcome of production schemes and massive improvements in management. Artificial genetic selection approaches targeted at developing genetically modified chicken lines with improved quantitative development as well as highly heritable qualitative features have gained favor over the last several years (Paxton et al., 2010). Poultry breeders held up with the rate of demand throughout the twentieth century by adapting to a variety of critical selections and breeding technical advances. It is projected that 400,000 pedigreed individuals representing 35–40 purebred lines from different firms will be the progenitors of approximately 400 billion commercial broilers on a global scale (Pollock, 1999). Developing a stable, better commercial broiler line will take 4.5 years if it is based on pure lines with varying reproductive lifespans. After more than 60 years of genetic selection, modern breeding techniques have produced exceptionally appealing, resistant lines that have increased in size by more than 300% while maintaining the proper body shape (Paxton et al., 2010). Poultry breeding targets are often guided by expectations for potential meat production. As a result, genetic selection is becoming more prevalent in modern broiler processing (Paxton et al., 2010).
1.1.3 Issues facing the Broiler industry in the US
The modern broiler farming industry, both in the United States and worldwide, faces a variety of challenges across areas like production, animal well-being, disease control, meat quality, financial factors, and environmental sustainability. These challenges collectively present hurdles to the sustainable operation of the industry requiring thorough attention and strategic actions. The broiler farming sector faces challenges related to animal welfare concerns that are increasingly being noticed by both industry professionals and consumers. These challenges are influenced by factors like bedding material, genetic selection, stocking density, and environmental stressors. The availability of bedding is becoming a concern in the broiler industry, potentially changing the options for growers to raise broiler chickens (Bilgili et al., 2009). Additionally, the industry has been focused on achieving lean growth with high muscle yield through modifications and specific breeding choices impacting productivity and efficiency significantly (Zukiwsky et al., 2021; Zuidhof et al., 2014). Stocking density has critical effects on returns in the broiler industry as higher stocking densities may lead to increased profits (Estevéz, 2007).
The intensification of broiler farming practices has raised worries about issues like leg health, skeletal problems, lameness, and diseases such as chondronecrosis with osteomyelitis (BCO) and necrotic enteritis (Fodor et al., 2022; Sassi et al., 2016; Wideman, 2016; Zhang et al., 2023). These problems do not only impact the well-being of broilers but also have significant financial implications for producers. Additionally, the use of antibiotics in the industry for growth promotion has caused concerns about the emergence of antibiotic pathogens that pose risks to both animal and human health (Cuker, 2020).
In addition to welfare issues, managing diseases is a challenge in broiler production. Diseases like avian pathogenic Escherichia coli, Clostridium perfringens, necrotic enteritis and inflammatory responses create obstacles in maintaining the health and productivity of broilers (Fancher et al., 2020; El‐Hack et al., 2022; Souza et al., 2022). The extensive use of antibiotics exacerbates this problem by contributing to the development of resistance to pathogens (Zhu et al., 2021). Moreover, worries regarding the safety of food including issues like Campylobacter contamination and the existence of Salmonella strains resistant to drugs trigger health concerns at stages of the food supply chain necessitating the implementation of stringent control protocols (Agunos et al., 2014; Pate et al., 2019).
Quality problems in meat production including issues like striping and woody breast muscle myopathies have become worries in the broiler industry affecting the overall quality and consumer satisfaction of broiler breast meat (Tijare et al., 2016). Moreover, the increase in breast muscle abnormalities in growing commercial broiler breeds poses challenges for both industry professionals and researchers requiring study and innovation to address these challenges (Nawaz et al., 2022).
Economic factors add another layer to the difficulties faced by the broiler industry. Adjusting tariff fluctuations, price disparities in the broiler market, and the necessity for food security pose obstacles to maintaining production and economic stability within the industry (Nkgadima and Muchopa, 2022). Additionally, shortages in labor, insufficient resources and inadequate transportation networks impede the growth and effectiveness of broiler farming operations (Suwarta and Hanafie, 2021).
The environmental impact of the broiler industry is also a cause for concern due to its footprint. Challenges such as managing nutrients, handling manure, and dealing with the consequences of poultry production call for sustainable methods and technological advancements to minimize negative impacts (Bryant et al., 2021). Moreover, dealing with heat stress in broiler production in tropical regions presents significant hurdles in maintaining both quality and quantity of production (Moustafa et al., 2021; Lu et al., 2018).
Addressing these challenges necessitates efforts from various stakeholders within the broiler sector including producers, researchers, policymakers, and consumers. Embracing progressions, implementing management techniques, adopting sustainable production systems, and establishing robust regulatory frameworks are key elements of a holistic approach to overcoming the intricate issues confronting the broiler industry. This approach is vital for ensuring its enduring viability and sustainability amidst a changing environment.
lameness in Broiler Chickens
Leg disorders
Broiler chickens are well known for their growth and cost-effectiveness on producing protein, making them a key part of the poultry industry. However, the focus on maximizing growth rates through breeding has resulted in imbalances in the development of organs in the muscle and skeletal systems (Tullo et al., 2017; Manohar et al., 2015). This has led to problems like leg weakness and disorders affecting the bird’s ability to walk normally, making them prone to conditions like lameness marked by bone deformities or stiffness (Gocsik et al., 2017; Aydin, 2018). The high occurrence of leg weakness, like lameness and other bone issues, raises significant concerns about animal welfare and production efficiency, contributing to increased morbidity and mortality rates in broiler chickens worldwide (Bessei, 2006; Bradshaw et al., 2002; Gocsik et al., 2017). Changes in anatomy due to breeding objectives, such as increased muscle mass and shifting center of gravity, contribute to problems like weakening bones, deformities, and osteoporosis (Rath et al., 1999; Paxton et al., 2010).
Lameness is worsened in birds with increased activity, resulting in prolonged periods of lying down and reduced walking activity (Weeks et al., 2000; Sherlock et al., 2010). Figure 5 shows several factors that play a role in causing leg issues in broiler chickens, such as genetics, species, gender, age, and infections (Kierończyk et al., 2017; Aydin, 2018). Moreover, environmental factors play a crucial role in the development and exacerbation of lameness. Factors such as nutrition, lighting patterns, exercise opportunities, and housing conditions significantly impact bone health and mobility in broiler chickens (Gocsik et al., 2017; Reiter, 2006). Furthermore, improper handling, transportation practices, and overcrowding can exacerbate skeletal stress and increase the incidence of lameness (Knowles et al., 2008).
The etiology of lameness is classified into three categories: degenerative disorders, metabolic disorders, and developmental diseases (SCAHAW, 2000). Subsequently, lameness has been classified into five categories according to the etiological factors responsible for its occurrence: nutritional disorders, viral infections, conformational challenges, metabolic irregularities, and environmental contaminants (Szafraniec et al., 2022). Conditions like varus valgus deformity and tibia dyschondroplasia, and infectious diseases like bacterial chondronecrosis with osteomyelitis (BCO) significantly contribute to lameness (Cook, 2000; Bradshaw et al., 2002). Although the connection between lameness and pain is not definitively established, the negative impact on animal health and well-being is widely recognized in the poultry sector (Gocsik et al. 2017).
BCO is identified as a factor leading to lameness in broiler chickens, highlighting the importance of implementing management strategies to tackle this prevalent issue (Al Rubaye et al., 2015). Despite the progress made in poultry farming methods, lameness remains an issue that requires studies and actions to enhance the bone health and movement of broiler chickens (Moura et al., 2006). By comprehending the factors that play a role in lameness, those involved can introduce strategies to reduce its occurrence and enhance the well-being of broiler chickens in the poultry sector.
Prevalence and Incidence of lameness
The poultry industry indicates Bacterial Chondronecrosis with Osteomyelitis (BCO) as a cause of lameness that poses challenges to both economic and animal welfare (Bradshaw et al., 2002, Wideman and Prisby, 2013; Dinev, 2012; Jiang et al., 2015; Gilley et al., 2014; Wijesurendra et al., 2017). This issue was identified as the most common cause of lameness in broiler flocks. It was first recognized in Australia, where Staphylococcus aureus was isolated from lesions in commercial broilers (McNamee and Smyth, 2000; Dinev, 2012). A subsequent study conducted in Victoria Australia revealed that BCO affects broilers at a high rate throughout their lives with around 28% of birds diagnosed with various lesions (Wijesurendra et al., 2017).
Recent findings from a survey conducted in the UK indicate that 30% of broilers exhibit gait abnormalities underscoring the widespread issue of lameness, within intensive poultry production setups (Caplen et al., 2012). The average occurrence of BCO and similar conditions has been documented to reach up to 57.1% highlighting the impact of these issues on broiler flocks (Bradshaw et al., 2002).
Furthermore, studies have identified Staphylococcus agnetis as significantly involved in BCO, resulting in lameness in broiler chickens (Szafraniec et al., 2020; Alrubaye et al., 2015). The prevalence of lameness due to BCO can be as high as 50% with mortality rates reaching up to 5% in affected flocks (McNamee & Smyth, 2000; Dinev, 2012; Oliveira et al., 2020). This condition affects both the femur and tibiotarsus equally showing its impact on the system of broiler chickens (Wijesurendra et al., 2017).
BCO has since been reported in broilers from additional nations, including Canada, Australia, Europe, and the United States of America (McNamee & Smyth, 2000; Bradshaw et al., 2002; Dinev, 2012; Wideman et al., 2012). Abnormalities of bone have been identified as the primary cause of broiler mortality and losses in Canada (McNamee and Smyth, 2000). Butterworth (1999) has reported that femoral head necrosis (FHN) is a frequently observed cause of lameness among broilers in the United Kingdom. Therefore, it has been shown that BCO is mostly responsible for leg difficulties (Bradshaw et al., 2002).
In Canada, long bone abnormalities have been recognized as the primary cause of lameness in flocks, resulting in a loss of 10% of the entire flock (Riddell and Springer, 1985). The incidence of birds killed owing to lameness ranged from 0.46 to 4.08% based on data collected from 51 broiler flocks in Western Canada (Riddell and Springer, 1985). Research in Northern Ireland revealed that a percentage of female and male broiler flocks were determined to be lame, with BCO found in 17.3% of culled chickens with leg abnormalities (McNamee et al., 1999; McNamee, 1998). Furthermore, lameness was prevalent in 0.38% of female broilers and 0.52% of male broilers, with only 27% of commercial broilers exhibiting restricted movement and 3% categorized as lame (Knowles et al., 2008). Recent years have seen the Farm Animal Welfare Council recognizing osteomyelitis as the primary cause of lameness in commercial broilers (Council and Britain, 1992). Various names for this disease have been documented, but BCO is considered the most appropriate one because it accurately describes the pathology, including necrotic degeneration, and indicates microbial infection involvement (Wise, 1975). BCO is reported to manifest as necrotic degeneration and bacterial infection mainly within the rapidly growing bones and joints in broilers (McNamee and Smyth, 2000; Bradshaw et al., 2002; Wideman et al., 2012).
In the case of an epidemic outbreak of BCO lameness in broilers, it is typical to experience a loss rate of up to 1.5% among infected flocks. However, in certain circumstances, the loss rate can be much higher, exceeding 15% of the entire flock (Rebello, 2019). Research estimates that 0.75% of all birds may have lameness attributable to BCO (McNamee & Smyth, 2000). Furthermore, a study conducted on 67 lame birds found that 64% showed gross degeneration of the femoral end mainly due to osteomyelitis, 25% expressed epiphysiolysis while the remaining 11% showed microscopic bacterial or osteochondritis lesions (Thorb et al., 1993). Investigations in Bulgaria also reported a high incidence of lameness responsible for over 15% of mortality in some broilers, with BCO the most prominent cause affecting more than 90% of these cases (Dinev, 2009; Wijesurendra et al., 2017).
Economic Impacts of Lameness
Lameness causes significant financial losses in the poultry industry, affecting broiler chickens and layers. This is known to cause decreased productivity, higher mortality rates, and increased culling rates. Lameness reduces the productivity of birds, causing pain and hindering essential functions such as access to water and food (Caplen et al., 2014; Kierończyk et al., 2017). As a result, lame birds experience weight loss owing to reduced mobility and lower feed intake, leading to lower profitability in the poultry industry. Poor feed conversion ratios, slow growth rates, and reduced egg production are all linked to lameness, which contributes to a 10–40% reduction in total profit because of decreased efficiency in processing broiler meat (Yalcin et al., 1998; Knowles et al., 2008; Aydin, 2018; Szafraniec et al., 2022).
The poultry industry annually loses about 12.5 billion birds worldwide owing to leg disorders (Cook, 2000; FAO, 2010). These disorders have profound economic implications, causing significant losses and costs related to growth interruptions and musculoskeletal system development, reaching 150 million dollars in the United States alone (Cook, 2000; Sullivan, 1994; Kierończyk et al., 2017; Aydin, 2018). Femoral head necrosis (FHN) is a condition that causes significant lameness worldwide. In the UK, FHN-related lameness costs around £4.7 million per year, while in Northern Ireland, the annual cost of FHN-related lameness is approximately £185,625 for male broilers and £118,000 for female broilers (Butterworth, 1999; McNamee et al., 1998).
Furthermore, the impact of lameness on the poultry industry extends beyond production costs to consumer prices. In the USA, the industry loses over $100 million annually, equivalent to $0.016 per broiler (Al-Rubaye et al., 2015; Aydin, 2018; Cook, 2000; Weaver, 1998). These losses affect production costs, ultimately impacting the retail prices of poultry products (Cook, 2000; Weaver, 1998). Consequently, the risk factors should be identified, and efficient management strategies should be implemented to reduce the economic impact of leg weakness and lameness (Knowles et al., 2008). By addressing these factors, poultry producers can minimize losses and enhance profitability within the industry.
The broiler production market has transformed significantly over the past few years. It has shifted from small-scale chicken farms to a more advanced and interconnected system run by a handful of corporations, turning it into a multi-billion-dollar industry (Lowder et al., 2009). The Farm Model estimates the economic burden of lameness by considering factors such as increased mortality, higher feed conversion rates, increased condemnation at slaughter, and decreased weight gain (Gocsik et al. 2017). This model offers insights into production costs, gross margins, and net profits per kilogram of broilers delivered (Gocsik et al., 2017).
Bacterial chondronecrosis with osteomyelitis (BCO)
Pathogenesis of BCO Lameness
BCO, previously known as femoral head necrosis (FHN), proximal femoral degeneration, or bacterial chondronecrosis, underwent a name change as researchers discovered that it also affects the proximal tibiotarsus and the fourth thoracic (T4) vertebra (Jiang et al., 2015; McNamee & Smyth, 2000; Bradshaw et al., 2002). Broilers are capable of gaining approximately 8 pounds in 8 weeks, a growth rate that necessitates a corresponding increase in skeletal frame strength (Wideman, 2016). The rapid bone growth mechanism is crucial to both BCO and lameness occurrences (Wideman, 2016; Wideman & Prisby, 2013). Long bone growth in young broilers involves elongation of growth plates at both ends of the bone shaft/diaphysis and an increase in diameter due to cortical bone remodeling (Bond et al., 1991; Applegate & Lilburn, 2002). Broilers exhibit a significant increase in femur and tibia length, along with mid-shaft diameter expansion, during rapid growth (Yair et al., 2012; Wideman, 2016). Compared to layers, broilers are more prone to lameness due to their disproportionate weight gain in relation to skeletal structure maturation (Wideman, 2016). Lameness incidence is higher in rapidly growing birds, and efforts to reduce early growth have been shown to mitigate the disease (Wideman, 2016).
BCO, which was previously known as femoral head necrosis (FHN), proximal femoral degeneration, or bacterial chondronecrosis, underwent a name change due to researchers discovering that it affects not only the proximal tibiotarsus and the fourth thoracic (T4) vertebra but also other areas (Jiang et al., 2015; McNamee & Smyth, 2000; Bradshaw et al., 2002). The rapid growth rate of broilers, which allows them to gain approximately 8 pounds in 8 weeks, necessitates a corresponding increase in skeletal frame strength (Wideman, 2016). The mechanism for rapid bone growth is crucial for both BCO and lameness occurrences (Wideman, 2016; Wideman & Prisby, 2013). Long bone growth in young broilers involves the elongation of growth plates at both ends of the bone shaft/diaphysis and an increase in diameter due to cortical bone remodeling (Applegate & Lilburn, 2002; Bond et al., 1991). Broilers experience a significant increase in femur and tibia length, along with mid-shaft diameter expansion, during rapid growth (Wideman, 2016; Yair et al., 2012). Compared to layers, broilers are more susceptible to lameness due to their disproportionate weight gain in relation to skeletal structure maturation (Wideman, 2016). Lameness incidence is higher in rapidly growing birds, and efforts to reduce early growth have been shown to mitigate the disease (Wideman, 2016).
A flooring system developed by Dr. Wideman has been found to cause lameness in growing birds by creating shear stress (Wideman et al., 2012). Numerous trials have demonstrated the susceptibility of different broiler product lines to BCO-related lameness, with some lines showing sire-effects (Al-Rubaye et al., 2017; Wideman et al., 2013, 2014). The onset of BCO lameness appears to involve mechanical micro-fracturing of poorly mineralized cartilage cell columns in the proximal growth plates, which is followed by colonization of osteochondrotic crypts by opportunistic bacteria (Wideman, 2016; Petry et al., 2018). These bacteria can be transmitted vertically from parent breeders to chicks or horizontally from contaminated hatcheries and eggshells (Stalker et al., 2010). Bacteria may enter the chick’s bloodstream through various routes, including the respiratory, gastrointestinal, or integumentary systems (Al-Rubaye et al., 2015; Wideman, 2016). Hematogenously distributed bacteria can reach both ends of the growth plate through vascular plexuses (Wideman, 2016). Understanding the anatomical composition of broilers’ blood supply is essential for studying lameness occurrence (Wideman & Prisby, 2013).
The pathogenesis of BCO is intricate, involving rapid bone growth leading to mechanical stress on immature growth plates, which in turn results in microfractures and cartilage clefts (Wideman et al., 2012; McNamee & Smyth, 2000; Bradshaw et al., 2002). This creates sites for bacterial colonization, which can occur through various routes such as the respiratory and gastrointestinal tracts, leading to systemic dissemination (Wideman, 2016). Stress-induced immunosuppression can worsen bacterial proliferation and dissemination (Wideman et al., 2012). The subsequent bacterial colonization leads to the formation of lytic regions and yellow exudate within affected bones (McNamee & Smyth, 2000).
Microscopically, BCO lesions exhibit clusters of bacteria within blood vessels surrounded by necrotic tissue, indicating advanced disease progression (Wideman et al., 2012). The severity of lesions is classified based on macroscopic features, which provide insights into disease progression (Jiang et al., 2015). Understanding the blood supply anatomy of broilers is essential for comprehending the pathogenesis of lameness associated with BCO (Wideman & Prisby, 2013). Therefore, a comprehensive understanding of BCO requires the consideration of both biomechanical factors and bacterial colonization dynamics (Wideman et al., 2012; McNamee & Smyth, 2000).
