Gram Research analysis shows that adding L-tyrosine, an amino acid, to the feed of older laying hens significantly boosts egg production and quality. In a 12-week study of 180 hens aged 71 weeks, those receiving 1 gram of L-tyrosine per kilogram of feed produced more eggs with thicker, stronger shells and higher-quality whites compared to control hens. The supplement works by increasing dopamine levels while reducing prolactin, a hormone that suppresses reproduction in aging birds.
Researchers found that adding L-tyrosine, an amino acid, to the diet of older laying hens improved egg production and quality. The study involved 180 hens that were about 71 weeks old, fed either a regular diet or one supplemented with L-tyrosine for 12 weeks. Hens receiving the supplement produced more eggs, had better feed efficiency, and laid eggs with stronger shells and higher quality whites. The amino acid works by increasing dopamine levels while decreasing prolactin, a hormone that suppresses reproduction. This discovery suggests L-tyrosine could help commercial farms maintain productivity in aging flocks.
Key Statistics
A 12-week research study of 180 laying hens found that dietary L-tyrosine supplementation at 1 gram per kilogram of feed significantly increased hen-day egg production and improved eggshell thickness, shell weight, and overall egg quality compared to unsupplemented control hens.
According to research reviewed by Gram, L-tyrosine supplementation in aged laying hens increased plasma dopamine and serum estradiol while reducing serum prolactin levels, demonstrating the supplement’s ability to modulate reproductive hormones that decline with age.
A 2026 study of 180 Atak-S laying hens showed that dietary L-tyrosine improved feed conversion ratio and increased the Haugh unit (egg white quality measure) by modulating gene expression through changes in promoter methylation patterns.
Research found that hens receiving the highest L-tyrosine dose exhibited upregulated expression of dopaminergic and reproductive signaling genes with corresponding promoter hypomethylation, showing a significant negative correlation between gene expression and promoter methylation levels.
The Quick Take
- What they studied: Whether adding an amino acid called L-tyrosine to chicken feed could help older laying hens produce more and better-quality eggs
- Who participated: 180 Atak-S laying hens that were 71 weeks old (equivalent to middle-aged for chickens), divided into three groups of 60 hens each
- Key finding: Hens receiving the highest dose of L-tyrosine (1 gram per kilogram of feed) produced significantly more eggs, had thicker, stronger eggshells, and better overall egg quality compared to hens on regular feed
- What it means for you: If you raise laying hens or consume eggs, this research suggests a simple dietary supplement could extend the productive lifespan of aging flocks, potentially improving egg quality. However, this study was conducted in controlled farm settings and would need further testing before widespread commercial use.
The Research Details
Scientists divided 180 older laying hens into three equal groups. One group ate regular feed (the control group), while the other two groups ate the same feed but with added L-tyrosine at two different amounts: a lower dose of 0.5 grams per kilogram and a higher dose of 1 gram per kilogram. All hens were monitored for 12 weeks, and researchers measured how many eggs they laid, the quality of those eggs, and various hormone and gene markers in their blood.
This type of study is called a controlled experiment because researchers carefully controlled what each group ate and measured the results. By comparing the three groups, they could determine whether L-tyrosine actually caused the improvements or if they happened by chance.
The researchers also examined molecular changes in the hens’ bodies, looking at hormone levels and how genes were being expressed. This deeper analysis helped explain the mechanism—how L-tyrosine actually works to improve egg production.
This research approach is important because it doesn’t just show that something works; it explains why it works. By measuring hormones and examining gene activity, the scientists demonstrated that L-tyrosine increases dopamine (a chemical messenger that boosts reproduction) while decreasing prolactin (a hormone that suppresses egg production). This mechanistic understanding makes the findings more credible and helps predict whether the supplement might work in other situations.
The study used a reasonable sample size (180 hens) with proper controls and multiple measurements. The researchers measured not just egg production but also specific quality markers and underlying biological mechanisms. However, this was a single study in one breed of chicken under controlled conditions, so results may not apply to all chicken breeds or farm environments. The study was published in a peer-reviewed journal, which means other experts reviewed the methods before publication.
What the Results Show
Hens receiving the highest dose of L-tyrosine (1 gram per kilogram of feed) showed clear improvements across multiple measures. They laid significantly more eggs per hen per day compared to the control group. Their feed conversion ratio improved, meaning they needed less feed to produce each egg—an important economic factor for farms.
Egg quality improved substantially in the supplemented groups. Eggshells became thicker and heavier, which means they’re less likely to crack during handling and transport. The Haugh unit (a measure of egg white quality) increased, indicating firmer, higher-quality whites. The yolk index and albumen index both improved, suggesting more nutritious, visually appealing eggs.
At the hormonal level, L-tyrosine supplementation increased dopamine and estradiol (the reproductive hormone) in the blood while reducing prolactin levels. Prolactin is the hormone that naturally suppresses egg production, so lowering it helps maintain productivity in aging hens. These hormonal changes were dose-dependent, meaning the higher the L-tyrosine dose, the more pronounced the hormonal shifts.
The researchers discovered that L-tyrosine works at the genetic level by affecting how genes are turned on and off. Genes involved in dopamine signaling and reproduction were more active in supplemented hens, while the gene for prolactin was less active. These changes occurred through a process called promoter methylation—essentially, chemical tags that control whether genes are expressed. The supplemented hens showed reduced methylation (fewer chemical tags) on genes that promote reproduction and increased methylation on the prolactin gene, which suppresses it. This molecular-level evidence strengthens the explanation for why the supplement works.
This research builds on existing knowledge that dopamine suppresses prolactin and that prolactin declines with age in laying hens. Previous studies suggested that age-related reproductive decline in chickens involves increased prolactin levels. This study is among the first to demonstrate that dietary L-tyrosine—a precursor to dopamine—can effectively counteract this age-related decline. The findings align with broader research showing that amino acid supplementation can improve reproductive function in animals.
This study was conducted in a controlled research setting with one specific chicken breed (Atak-S), so results may not apply to all laying hen breeds or to commercial farms with different management practices. The study lasted 12 weeks, which is relatively short; longer-term effects are unknown. The research doesn’t address cost-effectiveness—whether the improved egg production justifies the cost of the supplement. Additionally, the study was conducted in 2026, so long-term safety data and real-world farm performance data are still limited. The mechanism involves complex genetic changes that may vary between individual birds or different environmental conditions.
The Bottom Line
Based on this research, L-tyrosine supplementation at 1 gram per kilogram of feed appears effective for improving egg production and quality in laying hens over 70 weeks old. The evidence is moderately strong for this specific breed and age group, but farmers should consider testing it on a small scale before full implementation. Consult with a poultry nutritionist to determine if this supplement fits your operation’s economics and management system. Confidence level: Moderate (strong evidence in this study, but limited to one breed and controlled conditions).
Commercial laying hen operations with aging flocks would benefit most from this research. Backyard chicken keepers with older hens might also see improved egg production. This is less relevant for meat chicken producers or younger laying flocks still in peak production. Anyone considering this supplement should first verify it’s approved for use in their region and consult with a veterinarian or poultry nutritionist.
Based on the 12-week study period, improvements in egg production and quality should become apparent within 2-4 weeks of supplementation, with full benefits visible by 8-12 weeks. Hormonal changes likely occur within days, but measurable improvements in egg production take longer. Results may vary depending on the individual flock’s health status and management practices.
Frequently Asked Questions
Can L-tyrosine help older chickens lay more eggs?
Yes, research shows that L-tyrosine supplementation at 1 gram per kilogram of feed significantly increased egg production in 71-week-old laying hens over a 12-week period. The supplement works by boosting dopamine levels while reducing prolactin, a hormone that suppresses reproduction in aging birds.
How does L-tyrosine improve egg quality?
L-tyrosine strengthens eggshells by increasing shell thickness and weight, and improves egg white quality (measured by Haugh unit). The supplement modulates reproductive hormones and gene expression, resulting in measurably better eggs across multiple quality indicators.
What age should laying hens be before using L-tyrosine supplementation?
This study specifically tested hens at 71 weeks old (late-phase laying hens), so that’s the age range with proven benefits. The supplement targets age-related reproductive decline, making it most relevant for flocks past peak production age, typically 60+ weeks old.
How long does it take to see results from L-tyrosine supplementation?
The 12-week study showed measurable improvements in egg production and quality within this timeframe. Hormonal changes likely occur within days, but noticeable increases in egg production and shell quality typically appear within 2-4 weeks of supplementation.
Does L-tyrosine work for all chicken breeds?
This research was conducted on Atak-S laying hens, so results are most reliable for this breed. Effects on other breeds are unknown. Farmers should consult with a poultry nutritionist before implementing supplementation in different breeds or management systems.
Want to Apply This Research?
- Track daily egg production per hen and measure eggshell thickness weekly using a micrometer. Record feed consumption to calculate feed conversion ratio (pounds of feed per dozen eggs). Monitor these metrics for 12 weeks to assess whether supplementation improves your specific flock’s performance.
- If using the app to manage a laying flock, set a reminder to add L-tyrosine supplement to feed at the recommended dose (1 gram per kilogram). Log the date supplementation begins and set weekly check-ins to measure egg production, shell quality, and feed efficiency. Compare pre-supplementation baseline data with post-supplementation results.
- Create a dashboard tracking three key metrics: eggs per hen per day, average eggshell thickness, and feed conversion ratio. Set baseline measurements before supplementation begins, then monitor weekly for 12 weeks. Use the app to generate reports comparing supplemented versus non-supplemented periods, allowing you to quantify the actual benefit for your operation.
This research was conducted in a controlled laboratory setting with one specific chicken breed and may not apply to all laying hen breeds, farm environments, or management systems. L-tyrosine supplementation should only be implemented under guidance from a qualified poultry veterinarian or nutritionist. Always verify that any supplement is approved for use in your region and follows local agricultural regulations. Results may vary based on individual flock health, genetics, and management practices. This information is for educational purposes and should not replace professional veterinary or nutritional advice. Consult with a poultry specialist before making changes to your flock’s diet or management.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.