During autumn and winter, temperatures drop sharply, there is a large difference between morning and evening temperatures, and the weather is cold. This is a peak season for respiratory diseases in chickens. If prevention is inadequate, flocks may become lethargic, pant, cough, have difficulty breathing, and eat less, causing significant losses to poultry farmers. Therefore, understanding the causes of respiratory diseases and promptly taking comprehensive prevention and control measures can reduce their incidence and economic losses.
I. Feeding and Management Factors
As the autumn and winter seasons arrive, outdoor temperatures drop sharply. If cold-protection and insulation measures in the poultry house are inadequate, the flock may be exposed to cold and wind, triggering respiratory diseases. At the same time, cold weather, excessively low temperatures in the poultry house, excessive humidity, poor ventilation, high dust levels, and delays in manure removal can make the air inside the house polluted and the concentration of harmful gases too high, which can also easily cause respiratory diseases.
In addition, stress factors such as excessive stocking density, malnutrition, vaccination, sudden changes in rearing conditions, deficiencies of substances such as vitamin A, and the long-term or excessive use of a single disinfectant or antimicrobial drug can alter the normal microbial flora in the environment and damage the mucosal system. This can reduce the immunity and resistance of the respiratory mucosa and trigger respiratory diseases.
For prevention, first strengthen flock management and increase insulation and heating measures. At the same time, ensure appropriate ventilation to reduce dust in the poultry house, lower the concentration of harmful gases inside, and provide the flock with the required temperature and fresh air. Monitor changes in the weather at all times to prevent cold drafts and cross-drafts from affecting the flock. Repair the poultry house as needed to prevent disturbances from rats, wild birds, and other animals. Remove chicken manure promptly and thoroughly disinfect the poultry house and equipment regularly. Properly balancing temperature and air quality is an important measure for preventing respiratory diseases. Second, reduce the occurrence of various stress factors, as stress is an important factor that can trigger respiratory diseases. These factors include:
1, Environment: Keep the temperature, humidity, lighting, and ventilation inside the poultry house relatively stable, and avoid sharp fluctuations.
2, Management factors: promptly transfer the birds to another group, reduce stocking density, and manage them strictly in accordance with operating procedures.
3, Physiological factors: provide appropriate feed and strengthen resistance. The standard for metabolizable energy in the feed may be raised appropriately. Pay particular attention to ensuring that the vitamin content in the feed meets requirements, and make sure feed ingredients are free of mold and impurities. Ensure that drinking water is clean and adequate.
4, Preventive healthcare: vaccinate at the appropriate time, avoiding the peak laying period; select preventive medications appropriately and use suitable administration methods and routes. Also ensure good hygiene in the poultry house.
二、Bacterial disease factors
The most common bacterial diseases, such as infectious coryza in chickens, pullorum disease, and colibacillosis, may all present with respiratory symptoms, but each has its own characteristics.
1, Infectious coryza: At the onset of the disease, the bird sneezes and has thin nasal discharge, which gradually thickens and develops an unpleasant odor. When it dries, it forms pale yellow scabs. There is conjunctivitis and tearing; the eyelids and surrounding facial area become swollen, first red and then purplish-blue. The nasal mucosa is swollen, breathing is accompanied by rales, and the larynx and trachea are grayish-red and contain mucus.
2, Pullorum disease: It is highly harmful to chicks. Symptoms include closed eyes and dozing, a retracted neck and lowered head, shrill cries, the abdomen contracting and relaxing, difficulty breathing, and white, paste-like droppings around the vent, which sometimes block it. Mortality generally increases after 3 days of age.
3, colibacillosis: Symptoms include difficulty breathing, rales, and cyanosis of the mucous membranes. On necropsy, the air sacs may appear cloudy and thickened, with yellowish-white, caseous fibrinous exudate attached. Eye inflammation is occasionally seen, with blindness in one or both eyes and pus accumulating inside the eye.
The bacterial diseases mentioned above can readily occur at different stages of raising a flock or under various stress conditions. In such cases, preventive medication is essential. Some broad-spectrum drugs to which the bacteria are highly sensitive may be administered regularly, along with regular supplementation of vitamins, minerals, and other nutrients to improve the animals’ disease resistance. Poultry houses and their surroundings should also be disinfected regularly (for example, by disinfecting the birds in the house twice a week). Use an “all-in, all-out” system. When the house is empty, fumigation with formaldehyde and potassium permanganate is recommended. During the raising period, spray disinfection with highly effective, non-toxic disinfectants is advisable. The area outside the house should be spray-disinfected with 2%–3% caustic soda solution.
When respiratory disease symptoms occur in a flock, promptly confirm the diagnosis and take measures to control the disease as early as possible. For bacterial diseases, select medication appropriately based on antimicrobial susceptibility testing. For symptomatic treatment, cough suppressants and medications to relieve breathing difficulties may be used as appropriate.
III. Viral disease factors
Many viral diseases, such as Newcastle disease, avian influenza, infectious bronchitis, and infectious laryngotracheitis, can cause respiratory symptoms and may sometimes occur as mixed infections with bacterial diseases.
1, Newcastle disease: During an outbreak, symptoms include difficulty breathing, tracheal rales, sneezing, head shaking, and, in some cases, nasal discharge; cyanosis of the comb and wattles; yellow-green droppings; and congestion of the mucous membranes throughout the body. Necropsy may reveal mucus in the organs, cloudy air sacs, erosion and hemorrhage of the glandular stomach, and hemorrhage of the cecal tonsils and rectum, among other findings.
2, avian influenza: During an outbreak, severe respiratory symptoms occur, such as coughing, sneezing, rales, profuse tearing, swollen eyelids, and swollen, purplish combs and wattles. In some cases, the scales on the feet show purplish hemorrhaging, and the birds pass yellow, loose droppings. Necropsy may reveal bright-red hemorrhage in the glandular stomach papillae; white or caseous secretions in the oviduct; caseous secretions at the junction of the trachea and bronchi; and increased fibrinous exudate.
3, infectious bronchitis: The main forms include respiratory, proventricular, renal, and intestinal forms. The main symptoms of the respiratory form are coughing, sneezing, open-mouth breathing, rales, watery eyes, and nasal discharge. At necropsy, mucus or caseous exudate may be found in the trachea, and the air sacs may be cloudy and thickened. Laying hens commonly show decreased egg production and an increase in misshapen, thin-shelled, and faded eggs.
4, infectious laryngotracheitis: This is a severe respiratory disease characterized by difficulty breathing, gasping, coughing, and coughing up bloody-looking exudate. At necropsy, the laryngeal and tracheal mucosae are swollen, with hemorrhage and erosion.
For viral disease factors, the currently effective preventive measure is to establish a sound hygiene and disease prevention system. First, the poultry farm layout should be rational, and an “all-in, all-out” system should be implemented to establish disease-free flocks. Regularly disinfect the inside and outside of poultry houses and the drinking water, strictly control the entry of visitors to the farm, place a disinfection pool at the entrance to each poultry house and replace the disinfectant regularly, and ensure proper isolation. Prevent transmission by wild birds and rats. Second, carry out immunization and vaccination; a scientific and reasonable immunization schedule must be developed according to local conditions. Ensure immunization against diseases such as Newcastle disease, infectious bronchitis, and avian influenza. Where conditions permit, antibody testing may be conducted regularly. Flocks with low antibody levels or uneven antibody levels should receive booster immunization in a timely manner. Follow the vaccination procedures strictly to ensure the expected immune response. For certain viral diseases with high morbidity and low mortality, such as atypical Newcastle disease, carry out emergency immunization.
When treating respiratory diseases in flocks with medication, follow the principle of combining etiological and symptomatic treatment. Select antibacterial and antiviral Chinese and Western medicines, as well as symptomatic medications. At the same time, provide an oral solution containing electrolytes, multivitamins, amino acids, and glucose in the drinking water to supplement the nutrients required by sick poultry and alleviate autointoxication.
Four. Comprehensive prevention and control
1, Strengthen the foundation of biosecurity: strengthen the biosecurity system and eliminate five routes of transmission; conduct antibody testing and vaccination to improve specific antibody levels; select feed ingredients carefully and use as little new-crop corn as possible, while paying attention to mycotoxin issues; adjust feed formulations at the appropriate time to enhance the body's resistance.
2, Focus on key management priorities: ensure proper ventilation management by following the three ventilation principles, selecting three modes, and achieving three matches; ensure proper stress management to prevent cold stress, heat stress, and humidity stress.
3, Early detection, early isolation, and early treatment: Early detection: increase inspections of the chicken houses, observe symptoms in the flock, and give due attention to necropsies of dead chickens; early isolation: strengthen disinfection of infected flocks, reduce the movement of personnel and items between houses, and prevent the spread; early treatment: select sensitive drugs, use combination medication for symptomatic treatment, complete the full course of treatment, and focus on treating both the symptoms and the root cause.
In short, raising chickens in autumn and winter presents certain challenges. Only by strengthening management in all areas, implementing scientific biosecurity measures, reducing stress factors, feeding appropriately, improving the flock’s resistance, carrying out vaccination diligently, adhering to an “all-in, all-out” system, and establishing a disease-free flock can disease outbreaks be controlled and good economic returns achieved.