How Probiotics in Eggs Are Revolutionizing Poultry Farming
By altering gene expression in key organs, scientists are giving chicks a health advantage from their very first moments
If you've ever enjoyed a plate of chicken wings or a grilled chicken salad, you've benefited from the modern poultry industry. But behind that simple meal lies a complex challenge: how do we raise healthy chickens without overusing antibiotics? The answer might be as simple as injecting a beneficial cocktail into chicken eggs before they even hatch. Scientists are now exploring how these early interventions can "program" a chicken's immune system by altering how genes are expressed in key organs, leading to healthier birds and potentially transforming how we approach poultry farming.
A chick's immune system is in a race against time. While the development of immune organs begins during the embryonic stage, functional maturity takes approximately two weeks after hatching. During this critical window, maternal antibodies fade while the chicks' own immune cells remain immature, leaving them vulnerable to pathogens during the early post-hatch period—precisely when they are most susceptible to disease 1 .
This vulnerability has traditionally been addressed with various interventions after hatching. However, the concept of in ovo stimulation (literally "in the egg") represents a paradigm shift. The idea is to jump-start the immune system during its developmental phase, giving chicks a health advantage from their very first moments. This approach has gained significant traction as the poultry industry seeks sustainable alternatives to antibiotics, which have been widely used for growth promotion and disease prevention but contribute to the global threat of antimicrobial resistance 1 .
On the 12th day of incubation, the eggs were carefully injected. This specific developmental window was chosen because it allows the intervention to influence developing immune organs without disrupting earlier critical formation stages.
The eggs were divided into three groups:
After the eggs hatched, the chickens were raised under standard conditions until day 35. Then, researchers collected three key immune-related tissues—cecal tonsils (gut-associated immune tissue), spleen, and liver—from eight birds per group. They used quantitative PCR, a sensitive molecular technique, to measure the expression of specific genes related to immune function and metabolism 1 .
Physiological saline solution
Leuconostoc mesenteroides B/00288
Probiotic + 0.5% garlic extract
When the researchers analyzed the gene expression data, they discovered a complex pattern of changes that revealed how differently the probiotic and prophybiotic treatments affected the chickens' biology.
| Tissue | Treatment | Key Gene Expression Changes | Biological Interpretation |
|---|---|---|---|
| Cecal Tonsils | Probiotic (PB) | ↓ Pro- and anti-inflammatory cytokines | Potential reduction in gut inflammation |
| Spleen | Probiotic (PB) | ↑ AVBD1, ↑ IL1-β | Enhanced antimicrobial defense and immune activation |
| Spleen | Prophybiotic (PPB) | ↑ AVBD1 | Strengthened innate immunity |
| Liver | Prophybiotic (PPB) | ↓ Pro- and anti-inflammatory cytokines | Reduced inflammatory activity in metabolic tissue |
The results demonstrated that the effects were not uniform across tissues but showed distinct organ-specific patterns. The cecal tonsils (gut-associated immune tissue) and liver showed a general downregulation of both pro- and anti-inflammatory cytokines in the PB and PPB groups respectively, suggesting a potential calming effect on inflammation in these tissues. Meanwhile, the spleen showed upregulated AVBD1 (a defensin with antimicrobial properties) in both treatment groups, indicating enhanced innate immunity 1 5 .
| Treatment | Gene | Function | Expression Change |
|---|---|---|---|
| Probiotic (PB) | COX16 | Energy metabolism | ↑ |
| Probiotic (PB) | mTOR | Protein metabolism | ↑ |
| Probiotic (PB) | CYP46A1 | Lipid metabolism | ↑ |
| Prophybiotic (PPB) | SREBP1 | Cholesterol synthesis | ↓ |
| Prophybiotic (PPB) | SLC2A2 | Glucose transportation | ↓ |
The probiotic alone generally enhanced expression of genes related to energy, protein, and lipid metabolism, while the prophybiotic combination showed a more complex pattern that included reduced expression of genes related to cholesterol synthesis and glucose transport 1 . This suggests that adding the garlic component shifted how the probiotic influenced metabolic pathways, potentially offering more tailored effects on chicken health and meat quality.
To conduct such sophisticated experiments, researchers require specific biological tools and reagents.
| Reagent/Resource | Function in the Experiment |
|---|---|
| Leuconostoc mesenteroides B/00288 | Probiotic strain with anti-Salmonella and anti-Campylobacter activity |
| Garlic aqueous extract | Phytobiotic component providing immunomodulatory compounds |
| Physiological saline (0.9% NaCl) | Sterile injection solution for control group |
| RNA Extracol solution | Used to isolate and preserve RNA from tissue samples |
| Quantitative PCR (qPCR) | Method to precisely measure gene expression levels |
| ROSS308 hatching eggs | Standardized broiler chicken breed for poultry research |
| MRS broth culture medium | Used to grow and maintain probiotic bacteria |
The implications of this research extend far beyond academic interest. This study demonstrates that early-life interventions can have tissue-specific effects on both immunity and metabolism, potentially allowing farmers to raise healthier birds with fewer medications. The fact that these treatments caused no adverse effects on hatchability, chick quality, or production parameters in previous studies makes this approach particularly promising for commercial application 1 .
Different probiotic strains offer varied benefits. Another study showed that spraying eggs with Lactobacillus paracasei and L. rhamnosus prior to and during incubation significantly improved embryonic development, hatchability, and post-hatch performance. When continued after hatching, these probiotics led to improvements in body weight gain (8-15%), carcass weight (2.7-3.8%), and feed conversion ratio (reduced by 3-4.9%) 2 .
The concept of modulating gene expression through probiotics isn't limited to chickens. A 2025 study on human gut cells revealed that specific strains of Lactobacillus and Bifidobacterium can upregulate autophagy genes (a cellular "housekeeping" process) and exert anti-inflammatory effects, particularly when administered before inflammation begins 6 . This parallel research in human health strengthens the scientific foundation for how probiotics might influence gene regulation across species.
The science of in ovo stimulation represents a fascinating convergence of immunology, genetics, and agriculture. By understanding how to modulate gene expression during embryonic development, scientists can potentially "program" chickens for better health and productivity without relying on antibiotics. The distinct effects of different formulations—probiotics alone versus prophybiotics—suggest we may be able to fine-tune these interventions for specific outcomes, whether the goal is enhanced disease resistance, improved metabolic efficiency, or optimized meat quality.
While more research is needed to optimize combinations and understand long-term effects, one thing is clear: the path to healthier poultry may begin not in the chicken coop, but in the egg long before it hatches. As this field advances, consumers may one day enjoy chicken products with the knowledge that the birds were raised with scientifically advanced, sustainable methods that began programming their health before they even entered the world.