Researchers studied why some laying hens get broken breastbones more often than others. They looked at the genes of over 1,000 chickens and found that genetics plays a role in bone strength—about 22% of the difference between chickens comes from their genes. The study identified specific genes linked to calcium and vitamin D, which are important for strong bones. This discovery could help farmers breed chickens that are healthier and suffer fewer injuries, improving both chicken welfare and egg production.

The Quick Take

  • What they studied: Whether a chicken’s genes determine how likely it is to break its breastbone (keel bone), and which specific genes might be responsible.
  • Who participated: 1,060 white-feathered laying hens (chickens that produce eggs) living in a modern aviary system similar to commercial farms.
  • Key finding: About 22% of the differences in bone strength between chickens is due to their genes. Researchers found four specific genetic regions that together account for about 13% of the genetic differences in bone fracture risk.
  • What it means for you: If you care about chicken welfare or work in egg production, this suggests that farmers could breed stronger chickens by selecting for better genes. This could reduce painful injuries in laying hens.

The Research Details

Scientists took X-rays of 1,060 laying hens to measure how many bone fractures each chicken had. They then tested the DNA of all these chickens using a genetic test that looks at 60,000 different genetic markers—think of these as specific locations in the chicken’s genetic instruction manual. They used computer models to figure out how much of the bone fracture problem comes from genes versus other factors like housing or diet.

The researchers also did a genome-wide association study, which is like a treasure hunt through the chicken’s entire genetic code. They looked for genetic markers that appeared more often in chickens with more bone fractures compared to chickens with fewer fractures. This helped them pinpoint the exact genes involved.

They found that some genetic regions on chicken chromosomes 2 and 20 were strongly linked to bone fracture risk. They then looked up what these genes do in other animals to understand why they might affect bone strength.

This research approach is important because it moves beyond just looking at housing and nutrition—factors we already knew mattered. By studying genetics, scientists can now understand the biological reasons why some chickens are naturally more prone to broken bones. This knowledge could lead to breeding programs that select for naturally stronger chickens, which would be a permanent solution rather than just fixing the environment.

The study used a large sample size (over 1,000 chickens), which makes the results more reliable. The researchers used modern genetic testing technology and proper statistical methods. However, the study was done in one type of housing system, so results might differ in other environments. The findings are suggestive rather than definitive—more research would strengthen the conclusions.

What the Results Show

The main finding was that genetics accounts for about 22% of the variation in bone fracture susceptibility among laying hens. This is considered a moderate genetic influence, meaning that while genes matter, other factors like housing design, nutrition, and how much the chicken moves around also play important roles.

The researchers identified four specific genetic regions (called haplotype blocks) on chromosomes 2 and 20 that were associated with bone fracture risk. Together, these four regions explained about 13% of the total genetic differences in bone strength between chickens. This means these are likely the most important genetic areas affecting bone health in laying hens.

Interestingly, the genes found in these regions are involved in calcium and vitamin D processing—the same nutrients that humans need for strong bones. Five specific genes stood out: BCAS1, CYP24A1, PFND4, TSHZ2, and GDF6. These genes help control how the body uses calcium and vitamin D, which are essential for building and maintaining strong bones.

The researchers also noticed that one of the genetic regions linked to bone fractures was near other genes that affect how early a chicken starts laying eggs and how many eggs it produces. This suggests there might be a connection between early egg production and bone strength—chickens that start laying eggs very young might be more likely to have weak bones.

The study revealed that bone fracture susceptibility is influenced by multiple genes working together, rather than just one or two genes. This is important because it means farmers can’t simply breed for one trait; they need to consider the whole genetic picture. The connection to vitamin D and calcium metabolism suggests that nutrition might interact with genetics—even genetically strong chickens might develop weak bones if they don’t get enough calcium or vitamin D.

Previous research has shown that housing design and nutrition affect bone fractures in laying hens, but the genetic component was poorly understood. This study fills that gap by showing that genetics is moderately important. The findings align with human research showing that vitamin D and calcium metabolism genes affect bone health. The connection to egg production timing is new and suggests that the biological systems controlling reproduction and bone strength might be linked.

The study only looked at one type of chicken (white-feathered crossbreds) in one type of housing system, so results might not apply to all chicken breeds or all farm setups. The genetic markers identified explain only about 13% of the genetic influence on bone fractures, meaning other important genes haven’t been found yet. The study is observational rather than experimental, so researchers can’t prove that these genes directly cause stronger or weaker bones—only that they’re associated with bone fracture risk. Additionally, the research was conducted in a quasi-commercial setting, which may not perfectly match all commercial farms.

The Bottom Line

For egg producers: Consider selecting breeding stock based on genetic markers for bone strength, in addition to current selection for egg production. This could reduce bone fractures and improve chicken welfare. Pair genetic selection with good nutrition (adequate calcium and vitamin D) and appropriate housing design. Confidence level: Moderate—the genetics are real, but this is one study and more research would strengthen recommendations.

Egg producers and poultry farmers should care most about this research, as it offers a new tool to improve chicken health. Animal welfare advocates should care because reducing bone fractures improves chicken quality of life. Consumers who care about how laying hens are treated might find this relevant. This research is less directly relevant to people who don’t work with chickens or care about poultry farming.

If farmers start using genetic selection based on these findings, improvements would likely appear within 2-3 generations of breeding (roughly 2-3 years), as genetic traits are passed down through offspring. However, the full benefits would take longer to see across entire flocks.

Want to Apply This Research?

  • If you manage a laying hen flock, track the percentage of hens with visible keel bone fractures (detected by gentle palpation or X-ray) monthly. Record this alongside feed calcium and vitamin D levels, and note which breeding lines are used. Over time, you’ll see if genetic selection combined with nutrition optimization reduces fracture rates.
  • Implement a genetic testing program for breeding hens, selecting birds that carry the protective genetic variants identified in this study. Simultaneously, audit your flock’s calcium and vitamin D intake to ensure it meets requirements. Document which hens are selected for breeding and track their offspring’s bone health.
  • Establish a long-term tracking system that monitors bone fracture rates in your flock quarterly while recording which genetic lines are present. Compare fracture rates across different breeding groups to identify which genetic combinations produce the healthiest birds. Adjust breeding selections based on these results over multiple generations.

This research is specific to laying hens and does not apply to human health or nutrition. The findings are from one study in a specific housing system and should not be considered definitive guidance for all poultry operations. Farmers should consult with poultry veterinarians and geneticists before making breeding or management changes. This research suggests genetic associations but does not prove direct causation. Individual results may vary based on housing, nutrition, management practices, and other environmental factors.