Symptoms and Prevention and Treatment Methods of Chronic Respiratory Disease in Chickens

Ascites syndrome is a common non-infectious disease occurring in broiler chickens. It mainly occurs in fast-growing large broilers aged 20-40 days. Its characteristic manifestation is obvious fluid accumulation in the abdominal cavity, with severe damage to the heart, lungs, and liver. Although the incidence rate is not high, the mortality rate after onset is close to 100%.

Causes: This disease has multiple causative factors. In addition to the physiological and anatomical characteristics of broilers themselves, there are also environmental factors and secondary infection with pathogens after poisoning. Generally speaking, any factor that causes portal venous circulation disturbance or right heart failure can lead to ascites.

Excessively rapid growth. Because fast-growing large broilers grow quickly, the lung volume is not proportional to the increase in body weight. In order to meet the body's oxygen demand, pulmonary arterial pressure increases and blood flow increases, thereby increasing the burden on the heart, leading to right ventricular hypertrophy and dilation, and further causing pulmonary congestion, resulting in the appearance of large amounts of ascites.

The special physiological and anatomical characteristics of chickens. The lungs of chickens are fixed within the thoracic cavity, and the range for oxygen exchange in the pulmonary capillaries is insufficient, which also causes pulmonary hypertension and leads to pulmonary congestion.

Poisoning. Because feed contains toxic oils or salt, sulfonamide drugs, etc., poisoning directly damages the liver, causing liver lesions and leading to massive retention of ascites.

Environmental changes such as hypoxia, cold, and poor ventilation cause a decrease in blood oxygen concentration and accelerate heart beating, leading to cardiac dysfunction and resulting in systemic congestion, especially hepatic congestion.

Secondary infection with pathogens such as avian aspergillosis, colibacillosis, and salmonellosis, or certain viruses, causes lesions in the lungs, heart, and liver, leading to the appearance of large amounts of ascites.

Clinical symptoms: Affected chickens walk slowly, in a duck-like manner; in severe cases, they have difficulty standing, with the abdomen touching the ground, showing a penguin-like posture, and the abdomen is obviously swollen and dark red or bluish purple. On palpation, there is obvious fluctuation. The feathers are ruffled, the spirit is poor, breathing is rapid, and the comb and wattles are cyanotic. Some affected chickens develop diarrhea.

Pathological changes: There is a large amount of brownish-red or earth-yellow ascites in the abdominal cavity, sometimes clear and sometimes mixed with fibrinous protein clots; the liver is enlarged and congested, and sometimes perihepatitis occurs, with pericardial effusion and soft myocardium. The right ventricle is obviously dilated and the wall is thickened. Due to the pressure of ascites, the liver is enlarged and congested.

Prevention and treatment: According to the causes of the disease, corresponding measures should be taken:

1. Before 2 weeks of age, the protein and energy in the feed should not be too high.

2. Control lighting, and regularly adopt a rearing method of 23 hours of light plus 1 hour of darkness.

3. Reduce stocking density, and strictly prohibit feeding moldy or spoiled feed.

4. Do a good job in the environmental hygiene inside and outside the chicken house, carry out in-house disinfection with chickens present on time, pay attention to ventilation inside the house, remove ammonia and carbon dioxide in the house, and increase oxygen.

5. For affected flocks, carry out moderate feed restriction or reduce the energy level in the feed and take corresponding drugs for treatment. Add vitamin C at multiple times the normal amount in the feed (600 g/ton) for 5-7 consecutive days, then after half a month use it at the normal amount for 5-7 days; adjust the electrolyte balance, use Weishi Wei'an in drinking water for 3-4 consecutive days, and use Jizhong Shenbao in the evening to promote kidney function. Treat the primary disease of the flock, and promptly use antibiotics or antiviral drugs for treatment according to the incidence situation.

Experience: In the past, ascites in broilers was neglected merely as a symptom of other diseases. However, in recent years, with the rapid promotion of fast-growing large broilers, the probability of this disease occurring alone has become greater and greater. As a non-infectious disease, the harm it causes to the @#@230@#@ industry has become increasingly serious. Therefore, the breeding industry should pay sufficient attention to this disease. The occurrence of this disease is largely related to poor ventilation in the chicken house, but when ventilating, the problem of keeping the house warm must be properly solved.