Improving Broiler Chicken Production: Trends and Techniques

Introduction

Broiler chickens (Gallus gallus domesticus), also known as meat chickens, are birds reared for meat and have creamy white plumage. After years of cross-breeding and selection, broiler chickens were developed for meat production (Oviedo-Rondón et al., 2009). Over the years, meat chicken selection has focused on improving feed conversion efficiency, growth rate, meat yield, and quality. This has resulted in chickens with a high feed conversion ratio and fast growth rate; moreover, the meat is tender and widely accepted globally. The broiler industry has grown significantly due to the high demand for chicken meat. Broilers have become a popular alternative to beef and pork, partly due to their fast growth rates and lower production costs, with over 70 billion slaughtered annually worldwide (Mace & Knight, 2022). Poultry farming, particularly broiler production, is considered one of the most efficient animal husbandry methods (Gržinić et al., 2023). The industry continues to evolve with advancements in breeding, nutrition, and management practices to meet the growing demands for chicken meat.

 Broiler Chicken Breeds

Below are presented three broiler chicken breeds:

• Hubbard
• Cobb 500 
• Ross

Figure 1. Breeds of Meat Chickens (Broilers)

Source: Aviagen (2024). Retrieved from https://aviagen.com/eu/brands/ross/

Source: Cobb vantress (2024). Retrieved from https://www.cobbgenetics.com/

How Commercial Meat Chickens Have Evolved: A Look from 1957 to 2005

Over the last fifty years, artificial selection of domestic chickens has led to rapid growth rates and high carcass yields (Korver, 2023), allowing meat chickens to reach slaughter weights between 35 and 45 days of age (Figure 2). Broiler chickens grew over 400% larger, and their feed conversion ratio (FCR) improved by 50%. This translates to an average annual increase of 3.30% in their 42-day body weight and a 2.55% annual improvement in their FCR (Zuidhof et al., 2014; Neeteson et al., 2023).

Adapted from Zuidhof et al. 2014

Genetic Improvements in Broiler Chickens: Effects on Growth and Health

In the 1960s, meat chickens reached a market weight of about 2 kg in 9 weeks with a feed conversion ratio (FCR) of 2.5. Today, they can reach 2.5 kg in 5 weeks with a lower FCR of 1.5 (Fairchild, 2005; Aviagen, 2014). However, modern chickens have reduced activity levels and are prone to metabolic and leg disorders due to rapid growth (Bizeray et al., 2000; Kestin et al., 2001). They are also at higher risk of physiological imbalances and heart issues, such as ascites, from years of genetic selection for high breast meat yield and performance (Hartcher & Lum, 2020). In broiler chickens, rapid growth and increased muscle mass cause harmful side effects on their welfare (Bessei, 2006).

Common Health Challenges in Broiler Chickens 

Lameness and Leg Issues

Lameness is common in meat chickens, causing them to sit a lot by 5-6 weeks old due to leg pain (Figure 3). These chickens suffer poor blood circulation and bone development unlike their active wild ancestors. Lame chickens struggle to reach food and water, leading to starvation, dehydration, and possibly death (Weeks et al., 2000).

Understanding Foraging Behavior in Modern Broiler Chickens

Foraging behavior in chickens, also known as contra freeloading, is a situation whereby the chicken prefers to work for food even when the same source of food is within its reach or readily available (Lindqvist et al., 2006). Modern meat chickens rarely forage, unlike their wild ancestors (the red jungle fowl). They spend only 3% of their time searching for food compared to the 90%-time budget of the red jungle fowl (Dawkins, 1989; Weeks et al., 2000; Bizeray et al., 2000). This lack of foraging activity may be due to low motivation to explore their environment.

Welfare Issues in Broiler Chickens

Another welfare concern in meat chicken production is contact dermatitis, hock, and breast burn (Figures 4 & 5), which is caused by prolonged sitting of meat chicken in poor-quality litter. A wet litter with high urea content will have a burning sensation due to the accumulation of ammonia, which can ulcerate the bird's skin and cause lesions (Dawkins et al., 2004). 

Footpad Dermatitis in Broiler Chickens

Footpad dermatitis (FPD) in broilers is a condition where the skin on the footpad breaks down, often due to wet litter with high pH (Figure 4). This can lead to infections and necrotic lesions (Shepherd & Fairchild, 2010). FPD, also known as pododermatitis or foot burn, affects the bottom of the birds’ feet and can cause deep ulcers, abscesses, and tissue thickening. It not only downgrades chicken paws but is also a welfare concern. Hock burns and breast blisters are other types of contact dermatitis, with hock burns strongly linked to FPD (Meluzzi et al., 2008; Shepherd & Fairchild, 2010).

Figure 4. Foot pad Dermatitis (FPD) Adapted from Welfare Quality (2009) 

Scale for scoring FPD

0 = No evidence of foot pad dermatitis

1-2 = Minimal evidence of foot pad dermatitis

3-4 = Evidence of foot pad dermatitis

Hock Burn in Broiler Chickens: Causes, Symptoms, and Treatment

Hock burn is another type of contact dermatitis in broiler chicken. This is caused by prolonged contact with moist, dirty litter, often due to high stocking density (Louton et al., 2020). It appears as brown ulcers on the back of the leg (Bessei, 2006). It affects up to 88% of broilers in some flocks and is a key indicator of bird welfare (Kjaer et al., 2006). Birds with hock burns walk more slowly, indicating pain (McKeegan, 2010), and it helps to assess flock health and welfare issues (Hepworth et al., 2011; Saraiva et al., 2016).

Figure 5. Hock Burn in Broilers Adapted from Welfare Quality (2009)
Scale for scoring hock burn

0 = No evidence of hock burn

1-2 = Minimal evidence of hock burn

3-4 = Evidence of hock burn

Risk Factors for Hock Burn in Broilers

Broiler weight is a major risk factor for hock burn (Broom & Reefmann, 2005). Gender and litter quality also contribute (De Jong et al., 2005; McKeegan, 2010). While good litter type and quality help reduce hock burn, broiler weight is a more significant factor compared to litter characteristics (Louton et al., 2018).

Practical Tips to Improve Leg Health and Welfare in Broiler Chickens

Increasing the activity of young birds can reduce litter contact and improve leg health (Figure 6). To improve the welfare and productivity of broiler chickens, the following practices could be implemented:

• Perching and Foraging: Provide boxes and elevated platforms for perching. Scatter grains or worms in the litter to encourage foraging.

• Daily Adjustments: Adjust drinker heights, temperature, and ventilation daily according to broiler chicken standards and bird behavior. Making birds walk to reach feeders and drinkers.

• Enrichment Benefits: Environmental enrichment helps chickens perform natural behaviors like foraging, ground scratching, dust bathing, stretching, wing flapping, and perching. Allowing birds to range freely can improve their biological functioning, reduce abnormal behaviors, and enhance overall well-being.

These practices could improve leg condition and overall animal health. 

Figure 6. Increasing Activity in Young Birds

Conclusion

Research shows that allowing chickens to express natural behaviors by providing outdoor access is important for their welfare. However, there is significant variation in farm designs and management practices, and studies on the impact of outdoor access on broiler behaviour and welfare are limited. My next article will discuss how different rearing environments and management techniques affect meat chickens.

Keywords: Poultry farming, Broiler chickens, Meat production, Feed conversion efficiency, Growth rate, Meat yield, Animal Welfare, Animal Behaviour, Animal Breeding, Animal Genetics

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