What Is Poultry Ascites or "Water Belly" in poultry?
Ascites in poultry, also colloquially known as “water belly” in chickens, is a significant and complex metabolic syndrome within the poultry industry, particularly affecting fast-growing broiler chickens.
This non-contagious condition is characterized by the abnormal accumulation of fluid (plasma or lymph) in the poultry’s abdominal cavity. This fluid is typically yellow, clear, and sometimes contains fibrin clots.
Ascites in poultry is classified as a syndrome because it involves a group of signs and symptoms that appear together without a single, well-defined cause or treatment path. The syndrome can have both a genetic and a metabolic basis.
It is primarily triggered by a combination of genetic, management, environmental, and nutritional factors, including temperature and available oxygen. Chickens are more susceptible to this syndrome in environments with poor ventilation, at high altitudes, and among fast-growing broiler or those with existing respiratory diseases.
Causes of Poultry Ascites: Why Does Water Belly Occur?
Poultry ascites is a non-contagious and non-transmissible condition. Its primary cause lies in the poultry’s inability to deliver sufficient oxygen to its tissues and organs, a condition known as hypoxia. This oxygen deficiency triggers a chain of physiological reactions that ultimately lead to fluid accumulation in the abdominal cavity. This can result in significant mortality, especially between 5 and 7 weeks of age. This disease also occurs more frequently in male chickens.
All causes of poultry ascites eventually lead to increased pressure in the pulmonary arteries (pulmonary hypertension) and heart failure. When blood pressure in the lungs rises, the heart’s right ventricle must work harder to pump blood. This continuous strain over time causes the right ventricle to enlarge and weaken (right ventricular hypertrophy), eventually leading to right-sided heart failure. This failure results in blood backing up and increasing pressure in the main veins, particularly in the liver, which causes plasma to leak into the abdominal cavity and creates ascites.
Key Contributing Factors to Ascites:
The underlying factors contributing to poultry ascites can be classified into four main categories:
- Oxygen Deficiency (Hypoxia): The primary trigger for hypoxia is the main reason for ascites. Several conditions can lead to this oxygen shortage:
- High Altitude: In mountainous or high-altitude regions, the partial pressure of oxygen in the air is lower. This reduces oxygen levels in the poultry’s blood, increasing pulmonary blood pressure.
- Inadequate Ventilation: Stale air, increased concentrations of harmful gases like ammonia, carbon dioxide, and even carbon monoxide from brooders, along with reduced oxygen levels, hinder the poultry’s ability to absorb enough oxygen.
- Cold Stress: Cold temperatures increase the poultry’s metabolism to maintain body heat, which requires more oxygen. Even short-term cold stress can significantly increase susceptibility to ascites.
- High Stocking Density: Overcrowding reduces ventilation space and increases competition for oxygen.
- Dust and Pollutants: High levels of dust or pathogens in the air can damage the respiratory system and impair oxygen absorption.
- Genetics and High Growth Rate: Modern broiler chicken breeds have been genetically selected for very rapid growth. This accelerated growth dramatically increases the bird’s metabolic need for oxygen. Unfortunately, the size of their heart and lungs does not grow at the same pace as their muscles and body weight. This disproportionate organ development places immense strain on the cardiovascular system, making it prone to failure. Some genetic lines of poultry are naturally more predisposed to ascites.
- Metabolic and Nutritional Disorders: The type of feed and diet plays a crucial role in the development of ascites:
- High-Protein and High-Energy Diets: Diets formulated for rapid growth can increase the strain on the cardiovascular system.
- High Sodium (Salt): Excessive salt in the diet can lead to toxicity, increase pulmonary blood pressure, and cause ascites.
- Mycotoxins: Feed contaminated with mycotoxins like aflatoxin can damage the liver and vascular system, contributing to ascites. Other toxins, such as toxic fat and coal tar in disinfectants, can also cause the condition.
- Vitamin and Mineral Deficiencies: A lack of certain vitamins like E and C or the mineral selenium can negatively impact cardiovascular health.
- Diseases and Infectious Agents: Although less common, some infectious agents can play a role in ascites development by impacting the respiratory and cardiac systems:
- Respiratory Diseases: Viral infections (such as infectious bronchitis, Newcastle disease, avian influenza) or bacterial infections (like E. coli and Salmonella) that damage the lungs reduce oxygen absorption capacity, setting the stage for ascites.
- Fungal Infections: Fungi like Aspergillus fumigatus (the cause of aspergillosis or brooder pneumonia) can damage the lungs.
- Bacterial Endotoxins: Toxins produced by gram-negative bacteria can cause pulmonary blood vessels to constrict and increase pulmonary hypertension.
In summary, ascites is caused by either genetic factors or microorganisms. For ascites caused by genetics, feed restriction in young chicks has been shown to reduce the disease’s effects. Slower-growing chicks require less oxygen, allowing their heart and lung organs time to develop and adapt to the poultry’s oxygen needs.
For ascites caused by microorganisms, recent studies suggest that using dietary acidifiers as a feed supplement is effective.
Symptoms of Ascites in Poultry
Poultry ascites, a result of abnormal fluid accumulation in the bird’s abdominal cavity, is a key indicator of cardiorespiratory failure. This condition not only jeopardizes the poultry’ health but also causes significant economic losses to the poultry industry through increased mortality and decreased productivity. Flock mortality can range from 0.5% to 20%. A deep understanding of the underlying causes and the timely identification of ascites symptoms are crucial for effective flock management and loss mitigation.
Chickens with ascites are typically smaller than average, lethargic, and have ruffled feathers. Early diagnosis of this condition is possible through careful observation of clinical signs. Here are the most prominent and common symptoms of ascites in poultry:
- Abdominal Swelling (Abdominal Distension): The most characteristic sign of ascites is the noticeable swelling of the bird’s abdomen, caused by the buildup of clear, yellow, or sometimes cloudy fluid in the ventral cavity. The abdomen feels soft and fluid-filled upon palpation. This swelling can range from mild to severe and may be accompanied by abdominal pain.
- Respiratory Distress and Noises: Affected poultry often experience severe respiratory problems. The fluid accumulation exerts pressure on the lungs and air sacs, making breathing difficult. Symptoms may include panting and a gurgling sound. These signs can resemble heat stress in poultry but have a different underlying cause in ascites. Additionally, open-mouth breathing or wheezing sounds from the respiratory tract may be present.
- Reduced Activity and Lethargy (Immobility): Sick poultry are noticeably sluggish and inactive. They tend to sit more, isolate themselves from the flock, and lose interest in moving, foraging, and other natural activities.
- Decreased Feed and Water Intake: The bird’s appetite is significantly reduced, leading to less food consumption. Their desire to drink water may also decrease. This reduced intake results in weight loss in broiler, general weakness, and muscle wasting.
- Pale Comb and Wattles: Due to insufficient oxygen delivery to tissues (caused by heart failure and respiratory issues), the comb and wattles may appear pale or even bluish (cyanosis).
- Ruffled Feathers and Poor Hygiene: Sick poultry typically neglect their feather maintenance. Their feathers look ruffled, dirty, and disorganized, indicating general weakness and an inability to care for themselves.
- Difficulty Walking and Limping: In advanced stages, when the fluid accumulation is severe, the enlarged abdomen obstructs the bird’s natural gait, causing it to move with difficulty or to limp.
- Sudden Mortality: In severe, advanced cases of ascites, or when a bird is under stress, sudden mortality can be observed in the flock. This often occurs without any clear prior symptoms and can cause significant losses.
Related Article: Paralysis in Chickens: From Leg Lameness to Neck and Wing Paralysis
Changes in Feces of Chickens with Ascites
While changes in a poultry’s droppings are not a direct or primary sign of ascites, they can be observed as an indirect or secondary symptom. These changes are often the result of reduced feed and water intake, along with general weakness and potential digestive issues.
- Reduced Fecal Volume: Due to a significant decrease in appetite and feed consumption, the volume of droppings is noticeably smaller.
- Altered Fecal Consistency: Droppings may become drier than normal or, conversely, watery and loose due to secondary digestive problems or physiological stress.
- Changes in Fecal Color: Although ascites doesn’t directly change the color of droppings, side effects like liver problems or concurrent infections can cause a color change (e.g., yellow or green discoloration).
- Ruffled Feathers Around the Vent: Due to lethargy and a lack of self-grooming, the feathers around the bird’s vent may appear dirty and ruffled.
Related Article: Diagnosing Diseases from Chicken Droppings
Post-Mortem Findings in Ascitic Poultry (For Veterinarians and Experts)
For a definitive diagnosis and a better understanding of the pathophysiology of ascites in chickens, a post-mortem examination (necropsy) of deceased poultry is highly informative. Common findings include:
- Fluid Accumulation in the Abdominal Cavity: The presence of a large amount of yellow or amber-colored fluid in the coelomic cavity is the hallmark of ascites.
- Enlargement of the Right Ventricle of the Heart: This is the most common cardiac finding, indicating right-sided heart failure and an inability to pump blood to the lungs.
- Enlarged and Congested Liver: The liver may be enlarged and have a congested appearance. In some cases, it may show necrotic lesions.
- Pulmonary Edema and Blood Clots: Fluid accumulation in the lungs (pulmonary edema) and sometimes blood clots (thrombi) in the pulmonary vessels can be observed, indicating a severe disruption of respiratory and vascular function.
- Kidney Enlargement: In some cases, the kidneys may also be enlarged due to congestion or secondary issues.
Difference Between Poultry Ascites and Sudden Death Syndrome (SDS)
Poultry ascites and Sudden Death Syndrome (SDS) are two of the leading causes of mortality in broiler chickens. They are often confused due to their similarities, especially their shared outcome of sudden death. Both conditions are known as syndromes, not diseases, because their primary cause is not infectious or viral. Instead, they stem from complex factors like genetics, nutrition, and the environment. A syndrome is a group of signs and symptoms without a single, clear cause, whereas a disease has a specific cause and treatment pathway. In addition to sudden death, both syndromes are more prevalent in fast-growing broiler breeds and are particularly common in male chickens.
Despite these similarities, there are key differences in their causes and symptoms that enable accurate diagnosis. Ascites is primarily caused by cardio-respiratory failure. In this condition, the bird’s heart and lungs are unable to provide enough oxygen to support its rapid growth. This leads to clear symptoms before death, including abdominal swelling, respiratory distress, and lethargy. Although ascites isn’t an infectious disease, respiratory infections can act as a predisposing factor by reducing lung capacity. Necropsy findings clearly show yellow fluid accumulation in the abdominal cavity and enlargement of the right ventricle of the heart.
In contrast, Sudden Death Syndrome (SDS), also known as “chicken stroke,” has an unknown mechanism. It is believed to be linked to acute metabolic disorders and has no connection to infectious or viral agents. Unlike ascites, broiler with SDS usually show no visible symptoms before death and die suddenly while engaged in normal activities, such as eating. Necropsy of these broiler reveals a completely healthy-looking carcass with a fluid-free abdominal cavity, though their digestive tract is typically full of feed.
In summary, the key to distinguishing between these two syndromes is a careful examination of clinical symptoms (if present) and, most importantly, necropsy findings. Ascites is characterized by fluid accumulation and heart failure, whereas Sudden Death Syndrome involves the sudden death of an apparently healthy poultry with no fluid in the abdominal cavity.
Poultry Ascites Treatment
Ascites (water belly) in chickens, primarily seen in fast-growing broilers, is a sign of cardio-respiratory failure that occurs due to increased pulmonary blood pressure and right ventricular failure. Unfortunately,there is no definitive cure for ascites. Therefore, the main focus must be on preventing it. However, with proper management, symptoms can be reduced, and the spread of the disease can be controlled.
While there is no cure for ascites, some measures can help alleviate symptoms and improve the poultry condition:
- Improving Barn Ventilation: Proper and adequate ventilation, especially with negative pressure systems, is crucial to provide the birds with the necessary oxygen and remove harmful gases like ammonia, carbon dioxide, and carbon monoxide. This helps reduce stress on the respiratory and cardiovascular systems.
Article: To learn more about negative pressure ventilation systems in poultry farms, click the link.
- Using Vinegar: Adding 25 to 50 ccs of vinegar per 100 broilers to their drinking water once a day for 3 days can act as a natural diuretic and help reduce the volume of ascitic fluid.
- Controlling Respiratory Infections: It is vital to control both bacterial and viral respiratory infections, as they can create conditions that lead to ascites. Using appropriate medications like Echinamol (containing thyme and echinacea extracts with antibacterial, antiviral, and decongestant properties) can help improve respiratory symptoms and reduce the risk of ascites.
- Nutritional Supplements:
- Vitamins E and C: Adding 250 ppm of Vitamin E and 150-450 ppm of Vitamin C, along with organic selenium, to the feed can be effective. Vitamin E is a powerful antioxidant that prevents oxidative damage.
- L-Arginine: Adding 1% L-arginine to the diet can significantly reduce the right ventricular to total ventricular ratio and ascites mortality. L-arginine is a precursor to nitric oxide, a powerful pulmonary vasodilator.
- L-Carnitine: Using L-carnitine supplements can be beneficial by eliminating free radicals.
- Managing the Diet:
- Acidifiers and Prebiotics: In cases where ascites is caused by microorganisms like E. coli or Salmonella, acidifiers (by reducing the activity of gram-negative bacteria in the gut) and prebiotics can be effective.
- Reducing Sodium and Furazolidone: Reducing sodium and eliminating furazolidone from the diet can help decrease stress on the cardiovascular system.
Methods for Preventing Chicken Ascites
Preventing ascites is far more important than treating it and involves a combination of environmental, nutritional, and genetic management strategies:
Environmental and Ventilation Management:
- Adequate Ventilation and Air Quality Control: As mentioned in the treatment section, providing enough oxygen and removing harmful gases from the barn is critical. Special attention to oxygen levels is needed, especially in colder seasons when ventilation might be reduced.
- Reducing Dust and Controlling Ammonia: It’s essential to reduce dust and manage the bedding properly to prevent high ammonia levels (caused by high litter moisture), which can damage the respiratory tract.
- Inspecting and Maintaining Heating Systems: Ensuring heaters and heating systems are working correctly is important to prevent the production of harmful gases and ensure proper ventilation for their removal.
Temperature Management Ascites in Poultry:
- Maintaining Optimal Temperature: Keeping the barn at the right temperature, especially during the first week when chicks are most sensitive to cold, is crucial. Cold stress increases metabolism and oxygen demand, which puts more strain on the heart.
Nutritional Management: - Balanced Feed: Ensuring a proper balance of nutrients (energy, protein, fat, vitamins, and minerals) in the feed throughout the growth period is vital. Dietary factors that influence ascites include:
- Quantity and quality of dietary protein
- Dietary energy levels
- Dietary electrolytes
- Dietary antioxidants
Article: Poultry Feed Formulation
- Feed Restriction (Growth Control): One of the most effective prevention strategies is to slow down the broiler growth to reduce their metabolic oxygen needs. Any factor that leads to overly rapid growth in broilers increases the likelihood of ascites. For this reason, many poultry farmers, especially in high-altitude areas, consider factors in the broiler diet that slow down the growth process. For example, they may delay the chicks’ diet according to the catalog schedule by 2 to 3 days to allow the heart and muscle systems to synchronize. To achieve this, they might use mash instead of crumble or pellet feed during the first few days of rearing.
Water Quality: Clean and high-quality drinking water is essential for overall health and for preventing many diseases, including ascites.
Feed Texture: The type of feed texture can also affect consumption rates and, consequently, the bird’s growth.
Lighting Management:
- Intermittent Lighting Programs: Using intermittent lighting programs in the barn can prevent ascites by reducing feed consumption and lowering metabolism. Increasing the lighting period during the first two weeks of rearing can also reduce mortality from ascites, Sudden Death Syndrome, and leg problems.
Strain Selection:
- Genetic Resistance: Selecting breeds that have greater genetic resistance to ascites can be an effective way to reduce the incidence of the disease. Breeding companies are working to improve this trait in broilers. Research indicates that fast-growing broiler breeds are more susceptible to ascites due to their high metabolic need for oxygen and the disproportionate growth between their muscles and their cardio-pulmonary system. This issue is particularly important in high-altitude geographical areas, where environmental oxygen levels are lower, putting more strain on the bird’s respiratory system.
Among common commercial strains, some, like Arian and Hubbard, have been found to be more susceptible to ascites compared to others. A 2012 article confirms that different broiler strains have varying sensitivity to ascites. Specifically, this research indicates that Cobb 500 experiences the highest rate of ascites under stressful conditions (cold stress) and also has a higher growth rate. Arbor Acres also has a higher growth rate than Ross and shows increased hematocrit, indicating its susceptibility to ascites compared to Ross. Ross 308 showed the lowest susceptibility to ascites in this study.
- Controlling Other Diseases: Any factor that puts stress on the bird’s respiratory or cardiovascular system increases the risk of ascites. The careful control of infectious and respiratory diseases in the flock is crucial.
In general, any factor that causes excessive and rapid growth in broiler chickens increases the likelihood of them contracting ascites. Especially in higher-altitude locations, controlling the diet and restricting dark periods can reduce the disease in chicks. Increasing the lighting period during the first two weeks of rearing can reduce mortality from diseases like ascites, Sudden Death Syndrome, or flip-over syndrome, and leg problems in chicks. Overall, any factor that causes fast growth in broiler chickens increases the chance of them getting ascites. For this reason, many farmers, especially in high-altitude areas, consider specific factors in the broiler diet.
An Overview of Broiler Chicken Ascites Syndrome
Ascites (Water Belly)
Occurrence: Poultry ascites is a common disease worldwide, especially in cold and high-altitude environments.
Susceptible Species: Fast-growing broiler chickens and turkeys.
Age of Onset: (Information is missing from the original text, so I have left this blank.)
Causes: A non-contagious disease stemming from genetic factors, nutrition, growth rate, humidity levels, and available oxygen in the air.
Symptoms: Water belly, abdominal distension, reluctance to move, shortness of breath (dyspnea), and a bluish skin discoloration (cyanosis). Affected birds are smaller than average, lethargic, and have ruffled feathers. Mortality rates range from 0.5% to 2% within the flock.
Transmission of Ascites
Ascites is a non-contagious, genetic disease.
Article: A Guide for Poultry Farms and Farmers
