Introduction
The liver is a vital organ in poultry, essential for metabolism, detoxification, and nutrient synthesis—crucial for bird health and productivity in meat and egg production. Anatomically, it is a reddish-brown, bilobed organ located in the abdominal cavity. One of its primary functions is detoxification, as it filters toxins such as heavy metals, pesticides, and metabolic wastes (e.g., ammonia) from the bloodstream (Biochem, 2023).
Kupffer cells in the liver phagocytize pathogens and aged blood cells, further aiding in detoxification. Metabolically, the liver synthesizes and processes carbohydrates, fats, and proteins necessary for growth and reproduction. It releases glucose during fasting or increased energy demand via glycogenolysis and gluconeogenesis. Lipogenesis, or the conversion of carbohydrates to fats, is particularly active in laying hens due to elevated estrogen levels, which support yolk formation (Stevens, 2004).
The liver also synthesizes approximately 11% of total body protein in birds, producing blood proteins such as albumin, clotting factors, and immunoglobulins—crucial for maintaining osmotic balance, blood coagulation, and immune defense. Additionally, the liver stores fat-soluble vitamins (A, D, E, and K), vitamin B12, glycogen, iron, and copper, regulating nutrient availability during times of deficiency or increased demand, such as egg-laying. Maintaining liver health through appropriate diet and environmental management is critical, as deficiencies can lead to fatty liver syndrome and compromised immunity.
Anatomically, the poultry liver is located cranially in the abdominal cavity, ventral and caudal to the heart, and closely associated with the proventriculus and gizzard. Unlike in mammals, the avian liver consists of two main lobes: a larger, undivided right lobe and a smaller left lobe, which is divided into dorsal and ventral segments. The liver’s dark brown color often turns yellow after hatching due to high fat content.
The liver is encapsulated by a thin fibrous capsule and shows less distinct lobation because of reduced connective tissue. Hepatic lobules, the functional units of liver, are hexagonal and number up to 100,000 per lobe, each containing hepatocytes (about 80% of liver volume) and non-parenchymal cells. These lobules are organized around central veins and interconnected by sinusoids for blood flow. (Scielo, 2019; MSD Veterinary Manual, 2023).
The poultry liver receives oxygenated blood from the hepatic artery and nutrient-rich blood from the portal vein, supporting efficient metabolism and detoxification. Bile ducts from both lobes connect to the gallbladder and then to the duodenum, aiding fat digestion. Histologically, large, polyhedral hepatocytes with prominent nuclei and bile canaliculi enable effective bile secretion. Kupffer cells filter pathogens, supporting immune function. The liver’s vascularization, lobular structure, and integration with digestive organs underpin its roles in metabolism, detoxification, and nutrient synthesis—crucial for poultry health and productivity.
Important hepatic functions
- Fat metabolization: The liver is a multifunctional organ essential for detoxification, waste elimination, nutrient metabolism, and the storage of minerals and vitamins in birds. It is a primary site for lipogenesis, producing more fat than adipose tissue. Fat is metabolized from de novo synthesis, depot stores, and dietary sources. Due to birds’ poorly developed intestinal lymphatic system, dietary fatty acids are transported directly into the portal bloodstream as very low-density lipoproteins (portomicrons), which mostly pass through the liver before entering circulation—predisposing birds to hepatic fat accumulation(Cherian et al. 2002).
- Carbohydrate metabolization: With pancreatic assistance, the liver maintains blood glucose homeostasis. High glucose levels trigger conversion to triglycerides and glycogen (glycogenesis) for storage, while low levels prompt glycogenolysis and gluconeogenesis— converting glycogen, lactic acid, amino acids, and lipids into glucose as needed (Akers et al. 2013)
- Protein metabolization: Protein metabolism is also significant, with 11% of total bird protein synthesis occurring in the liver. Enterocytes absorb amino acids, which are transported via the portal vein to the liver and then distributed to tissues. Surplus amino acids are catabolized; hepatocytes deaminate them to produce ammonia and keto acids. Ammonia, toxic to birds, is primarily converted to uric acid in the liver—with only about 17% of uric acid synthesized by the kidney (Chin and Quebbemann, 1987).
- Metabolization of minerals and vitamins: The liver stores fat-soluble vitamins (A, D, E, K), vitamin B12, and minerals like copper and iron. It also participates in vitamin D3activation and stores minerals released from erythrocyte breakdown for reuse (Akers et al. 2013).
- Detoxification: The liver transforms endogenous and exogenous fat-soluble toxins—such as pesticides, heavy metals, drugs, and metabolic waste—into more water-soluble forms for excretion via the kidneys and gall bladder. Kupffer cells further protect birds by phagocytosing blood-borne microbes.
Challenges to Poultry Liver Health
The health of the poultry liver is paramount to the overall well being and productivity of birds. However, various challenges—primarily poor nutrition, mycotoxin exposure, and infections—pose significant threats to liver function and contribute to metabolic disorders.
Poor Nutrition
Nutrition critically influences poultry liver health. Imbalanced diets in protein, energy, and essential nutrients can cause Fatty Liver Syndrome (FLS), especially in high-producing laying hens on high-energy diets with limited exercise. Excess calories, mainly from carbohydrates and fats, lead to obesity and liver enlargement, making the liver soft and prone to damage and sudden death. An improper protein-to-energy ratio worsens fat buildup by limiting lipoprotein synthesis needed for fat transport out of the liver. Nutrient deficiencies, such as in calcium, further impair liver metabolism. Optimizing macronutrients, supplementing amino acids, vitamins, bioactive compounds, and modulating gut microbiota with probiotics and prebiotics help maintain liver health and prevent FLS (Borda-Molina et al., 2025; Ciurescu et al., 2020).
Fatty liver
Excessive fat accumulation in the liver, often linked to nutrient imbalances and metabolic disorders, can lead to various clinical signs. Affected birds commonly exhibit obesity, pale or shrunken combs with dandruff-like flakes, dull or discolored feathers, and lethargy.
Fatty liver haemorrhagic syndrome (FLHS)
FLHS primarily affects caged layer hens during peak production. It is marked by sudden death, liver rupture, hemorrhage, and massive fat accumulation in the liver and abdominal cavity (Crespo et al., 2003). Overfeeding carbohydrates, especially corn, is a leading cause. Backyard chickens may be less affected due to increased exercise. However, stressors like confinement and high temperatures make caged birds more susceptible. Older hens are at higher risk, even under ideal conditions.
Mycotoxins
Mycotoxins are toxic metabolites from molds contaminating feed grains, posing serious risks to liver health. Hepatotoxic mycotoxins like aflatoxin B1 and ochratoxin impair detoxification and metabolism, causing liver enlargement, fatty degeneration, necrosis, and irreversible damage (Ralco Agriculture, 2023). Chronic exposure results in pale, brittle livers, decreased productivity, and histopathological findings such as hepatocyte necrosis, bile duct hyperplasia, and inflammation (PMC, 2024). Additionally, mycotoxins suppress immunity and intestinal health. Ochratoxin induces oxidative stress, while trichothecenes promote apoptosis; their combined effects exacerbate liver damage.
Infections
Spotty Liver Disease:
Caused by Campylobacter hepaticus, this condition affects both free-range and caged systems. It is identified by white liver spots, reduced egg production, and increased mortality (Ralco Agriculture, 2023).
Viral Inclusion Body Hepatitis (IBH):
Caused by avian adenoviruses, IBH primarily affects broilers aged 3–8 weeks. It leads to sudden mortality (up to 30%), pale combs, and depression. Clinical signs include depression, pale combs, and high mortality. Necropsy reveals enlarged, yellow, crumbly livers with hemorrhages and intranuclear inclusion bodiesin hepatocytes, as well as enlarged, pale, mottled kidneys. IBH is often associated with immunosuppressive diseases like Infectious Bursal Disease or Chicken Infectious Anemia (Dinev, 2023).Prevention includes avoiding hatching eggs from infected flocks and limiting wild bird access (Dinev, 2023).
Mitigating Strategies
- Nutritional Management
- Balanced Diet Formulation: Maintain appropriate calorie-to-protein ratios. Supplement essential nutrients like vitamins B12, E, and choline to support fat metabolism. Monitoring feed intake and body weight regularly allows producers to adjust diets accordingly to prevent obesity and associated liver issues.
- Lipotropic Agents: Add choline (250 ppm in rearing; 500–1000 ppm during production), methionine, and inositol.
- L-Carnitine: Facilitates mitochondrial fatty acid oxidation by transporting long-chain fatty acids into the mitochondrial matrix, where they are oxidized to produce energy, thereby preventing hepatic lipidosis (Hoppel, 2003).
- Antioxidants and Mycotoxin Binders: Use vitamin E, selenium, and feed additives to neutralize toxins and oxidative stress.
- Other nutritional interventions: Dietary fiber promotes gut microbial fermentation; phytogenics (such as curcumin and oregano oil) offer hepatoprotective and antibacterial effects; omega-3 fatty acids support the liver-gut axis by reducing pro-inflammatory cytokines and boosting anti-inflammatory mediators, thereby improving liver health (Calder, 2015); and in ovo stimulation enhances hepatic antioxidant enzyme activity (Das et al., 2021).
- Biosecurity Measures
- Implement strict biosecurity: control access, sanitize equipment, monitor health, and maintain optimal housing and ventilation (Borda-Molina et al., 2025; Sciendo, 2025).
- Disease Prevention Strategies
Immunotherapy: Interleukin-2 (IL-2) enhances T-cell activity; interferon-gamma (IFN-γ) boosts innate immunity and reduces hepatic pathogens (Rothwell et al., 2004).
Vaccination Programs: Vaccinate against viral pathogens like adenoviruses to prevent viral hepatitis and related conditions (PubMed, 2016).
- Stress Reduction
Reduce environmental and handling stressors to improve metabolic and immune resilience.
- Genetic and molecular methods
Selective breeding for genes related to gut integrity (e.g., occludin, claudin) and liver detoxification (e.g., cytochrome P450 enzymes) enhances disease resistance. CRISPR-Cas9 enables targeted gene editing to improve traits such as antioxidant enzyme activity and antimicrobial peptide production (Gao et al., 2023).
Conclusion
Maintaining poultry liver health is vital for productivity and overall well-being. The liver’s central role in detoxification, metabolism, and nutrient storage makes it especially vulnerable to dietary imbalances, toxins, and infections. Conditions like Fatty Liver Syndrome, mycotoxin-induced liver damage, Spotty Liver Disease, and Inclusion Body Hepatitis pose significant threats. A comprehensive approach—combining optimized nutrition, biosecurity, vaccination, and stress reduction—can preserve liver function, enhance productivity, and support sustainable poultry farming.
by Dr. Nagesh Sonale 1, Dr. Monika M 2, Dr. Abhijit 3
1 Senior Technical Manager, Carus Laboratories Pvt Ltd.,
2 Scientist, ICAR-IARI, Barhi, Hazaribagh, JH,
3 Asst. Professor, IVSAH, SOA, Bhubaneswar
