According to Gram Research analysis, dietary supplements including garlic extract, fennel extract, and progesterone appeared to increase female chick production in a study of 100 layer breeder hens, while testosterone increased male chicks. However, these differences were not statistically significant (P = 0.056), meaning they could have occurred by chance. The study suggests diet may influence offspring sex ratios, but larger research is needed to confirm these preliminary findings.
Researchers tested whether adding hormones, garlic, and fennel to chicken feed could influence the sex of their offspring. In a five-week study with 100 layer breeder hens, scientists found that fennel and garlic extracts appeared to increase female chicks, while testosterone increased male chicks. The effects weren’t strong enough to be completely certain, but the results suggest that what we feed breeding chickens might influence whether they produce more male or female offspring. This could have practical applications for poultry farming.
Key Statistics
A 2026 research article published in PLoS One involving 100 layer breeder hens found that fennel extract increased serum testosterone levels compared to control diet (P = 0.057), suggesting plant extracts may influence reproductive hormones in chickens.
In a five-week study of 100 breeder hens, garlic and fennel extracts appeared to increase female offspring sex ratios while testosterone increased male ratios, though differences were not statistically significant (P = 0.056), indicating results may be due to chance.
A 2026 study of 100 layer breeder hens found that dietary treatments significantly influenced embryo development rates (P < 0.05), with testosterone producing the lowest female sex ratio and blood glucose levels.
The Quick Take
- What they studied: Whether adding sex hormones, garlic extract, or fennel extract to chicken feed could change the ratio of male to female chicks born from those chickens.
- Who participated: One hundred layer breeder hens (chickens raised for egg production) that were 65 weeks old, divided into five groups of 20 hens each, studied over five weeks.
- Key finding: Fennel and garlic extracts appeared to increase the number of female chicks, while testosterone increased male chicks, though these differences were not statistically significant (P = 0.056).
- What it means for you: If confirmed in larger studies, farmers might be able to influence chicken offspring sex through diet, which could help with farm planning. However, these results are preliminary and need more research before practical use.
The Research Details
Scientists divided 100 layer breeder hens into five equal groups. One group ate normal chicken feed (the control group), while the other four groups ate the same feed but with one added ingredient each: testosterone hormone, progesterone hormone, fennel extract, or garlic extract. The study lasted five weeks. Researchers collected blood samples from the hens in weeks three and five to measure hormone levels and blood sugar. At the end of week five, they collected eggs, incubated them (kept them warm to develop), and tracked how many male versus female chicks hatched.
This type of study is called a completely randomized design, which means each group had an equal chance of getting any treatment. This helps ensure the results aren’t biased. The researchers used standard laboratory methods to measure hormone levels in the blood and tracked embryo development in the eggs.
Understanding how diet affects offspring sex could help poultry farmers plan their operations more effectively. If certain natural ingredients like garlic and fennel can influence sex ratios, this might offer a safer alternative to hormone treatments. The study also helps us understand how nutrition affects reproduction at a biological level.
This study had a reasonable sample size (100 hens) and used proper scientific controls. However, the main findings were not statistically significant (P > 0.05), meaning the differences could have happened by chance. The study was relatively short (five weeks) and only tested one breed of chicken. The results are interesting but preliminary and would need to be repeated in larger studies before drawing firm conclusions.
What the Results Show
The fennel extract appeared to increase testosterone levels in the hens’ blood compared to the control group, though this difference was borderline (P = 0.057, meaning it’s close to but not quite statistically significant). Garlic extract, fennel extract, and progesterone all appeared to increase the percentage of female chicks born, while testosterone treatment appeared to increase male chicks. However, these differences in sex ratios were not statistically significant (P = 0.056), meaning they could have occurred by random chance.
The treatments did have a significant effect on the percentage of embryos that developed properly (P < 0.05), suggesting that the added ingredients influenced how well eggs developed. Interestingly, the testosterone group had the lowest percentage of female chicks and the lowest blood glucose (blood sugar) levels, while the progesterone, fennel, and garlic groups had the highest female percentages and highest blood glucose levels. This pattern suggests the treatments might work by affecting blood sugar levels in the hens.
Blood glucose levels showed numerical differences between groups but were not statistically significant (P = 0.076). The researchers noted that embryo development rates were significantly affected by the treatments, suggesting these ingredients influence how well eggs develop into chicks. The correlation between blood glucose levels and sex ratio suggests that metabolism (how the body processes energy) may play a role in determining offspring sex.
Previous research has suggested that diet and hormones can influence sex ratios in various animal species, though the mechanisms aren’t fully understood. This study adds to that body of knowledge by testing natural plant extracts (garlic and fennel) alongside synthetic hormones. The findings align with earlier research suggesting that metabolic factors like blood glucose may influence reproductive outcomes, though this specific application to chicken sex ratios is relatively novel.
The main limitation is that the primary findings were not statistically significant, meaning we can’t be confident the effects are real rather than due to chance. The study only lasted five weeks, which may not be long enough to see full effects. Only one breed and age of chicken was tested, so results may not apply to other chicken types. The sample size, while reasonable, could be larger for more definitive results. The study didn’t test combinations of treatments, only individual ingredients. Finally, the mechanism by which these ingredients might affect sex ratios isn’t fully explained.
The Bottom Line
Based on this preliminary research, there is low-to-moderate confidence that garlic and fennel extracts might influence offspring sex ratios in chickens. However, these findings need confirmation in larger, longer studies before farmers should change their practices. If you’re involved in poultry farming, monitor emerging research but don’t implement these dietary changes based on this single study alone.
Poultry farmers and hatchery operators should be aware of these findings as they develop. Researchers studying animal reproduction and nutrition should follow up with larger studies. The general public may find this interesting for understanding how diet affects biology. Those not involved in chicken farming can view this as basic science research with potential future applications.
If these effects are real, they would likely appear within one breeding cycle (a few weeks), since the study saw results within five weeks. However, larger studies would need months to years to confirm these findings before practical recommendations could be made.
Frequently Asked Questions
Can you change a chicken’s baby chick sex by changing what you feed the mother chicken?
A 2026 study suggests garlic and fennel extracts may increase female chicks while testosterone increases males, but the effects weren’t statistically significant. Larger studies are needed to confirm whether diet truly influences chick sex ratios in practical farming situations.
Does fennel extract affect hormone levels in chickens?
Research from 2026 found fennel extract appeared to increase testosterone levels in breeder hens compared to control diet (P = 0.057), though this difference was borderline and not definitively significant. More research is needed to confirm this effect.
What’s the connection between blood sugar and chicken offspring sex?
A 2026 study observed that treatments increasing female chick ratios also increased blood glucose levels, while testosterone (which increased male ratios) decreased blood glucose. This suggests metabolism may play a role in determining offspring sex, though the exact mechanism remains unclear.
Are natural extracts like garlic safer than hormones for influencing chicken sex ratios?
The 2026 study tested both synthetic hormones and natural extracts, finding similar effects on sex ratios. However, safety comparisons weren’t evaluated. Natural doesn’t automatically mean safer—both types need further research before practical recommendations.
How long would it take to see results if I added garlic to chicken feed?
The study observed potential effects within five weeks of dietary supplementation. However, these preliminary findings need confirmation in larger studies before farmers should expect reliable results from dietary changes.
Want to Apply This Research?
- If you raise chickens, track the sex ratio of chicks hatched from hens fed different diets over multiple breeding cycles. Record the specific diet ingredients and percentages, then compare hatch sex ratios month-to-month to identify patterns.
- Poultry farmers could experiment with adding garlic or fennel extract to breeder hen feed in small amounts and track resulting chick sex ratios, while maintaining detailed records of feed composition and hatch outcomes for comparison.
- Maintain a long-term log of feed ingredients, hormone or extract additions, hatch dates, and resulting sex ratios across multiple breeding cycles. Use the app to identify correlations between dietary changes and offspring sex distribution over time.
This research is preliminary and the main findings were not statistically significant. These results should not be used to make changes to poultry farming practices without consultation with a veterinarian or poultry nutrition specialist. The study was conducted on one breed of chickens over a short time period and has not been replicated in larger populations. Anyone considering dietary interventions in breeding animals should consult with qualified agricultural professionals and wait for larger, confirmatory studies before implementation. This article is for informational purposes only and does not constitute veterinary or agricultural advice.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.