I. Overview
Ammonia is a colorless gas with a strong, pungent odor. Ammonia poisoning in chickens occurs from time to time on poultry farms, particularly in winter and early spring. It is more common in modern enclosed poultry houses and intensive poultry farms than in open systems. Mild poisoning can slow chickens’ growth and development, reduce feed conversion efficiency and egg production, and weaken the flock’s resistance, making diseases such as Newcastle disease, colibacillosis, and chronic respiratory disease more likely to occur. Severe cases can cause chicken deaths, resulting in considerable economic losses for poultry farms.
[Causes]
When the temperature and humidity inside a poultry house are high, accumulated manure and bedding can ferment and produce large amounts of ammonia if they are not removed promptly and the house is not ventilated. In addition, when chickens develop coccidiosis or enteritis, changes in the intestinal environment and microbial community can disrupt digestion. This increases the amount of undigested protein in the manure, which, in turn, leads to the production of more ammonia through bacterial activity.
II. Clinical Signs
In the early stages of poisoning, affected chickens appear depressed and have reduced appetites. They may hold their heads low or tuck them under their wings, stand motionless, huddle, prefer to lie down, have ruffled feathers, pant, and breathe rapidly. They may keep their eyes closed or show photophobia, and their tears are serous. Nasal discharge may flow from the nostrils. They may shake or toss their heads from time to time, scratch their eyes with their toes, and make loud coughing and wheezing sounds. Some have difficulty standing and stagger when walking. In the middle stage, the oral mucosa becomes congested, and saliva and foam may flow from the mouth. The conjunctiva and cornea become congested; some chickens develop swollen eyelids or corneal opacity. In some affected chickens, a layer of white, membranous connective tissue forms over the cornea, causing conjunctivitis and blindness. The skin and comb turn dark purple. The chickens then breathe more slowly; some pass watery feces, and their body temperature falls. Severe cases die from respiratory distress.
III. Pathological findings at necropsy
The faces of dead chickens are swollen; gray mucus flows from the nasal cavity; the larynx is flushed, hemorrhagic, and edematous; the tracheal rings are often congested or hemorrhagic; the lungs show hemorrhage or congestion and are dark purple; the heart is enlarged, with black necrotic foci in the myocardium, and petechial hemorrhages in the coronary fat; the liver is swollen, fragile, and easily crumbled; the duodenal and rectal mucosae show diffuse hemorrhage; rigor mortis is incomplete, and no obvious lesions are seen in other organs.
IV. Diagnosis
A preliminary diagnosis can be made based on the clinical symptoms, the onset and mortality, and the pathological findings at necropsy.
V. Prevention and control
[Preventive measures]
(1) Remove manure promptly and replace bedding. To prevent ammonia poisoning, manure and bedding in the chicken house should be removed promptly. This is particularly important for broilers kept on litter; manure and bedding should be cleared, and the bedding replaced promptly.
(2) Improve ventilation and keep the air in the chicken house fresh. This is particularly important in winter: while maintaining warmth, attention must also be paid to removing pollutants and moisture from the house. According to tests, when a person enters the chicken house and smells ammonia but experiences no irritation to the nose or eyes, the ammonia concentration is approximately 10–20 milligrams per kilogram, the minimum level detectable by the human sense of smell, and it causes no harm to chickens. If a person entering the chicken house experiences nasal irritation and tearing, and a stinging sensation in the nasal mucosa, and takes several minutes to adapt, this indicates an ammonia concentration of 25–35 milligrams per kilogram. If a person has difficulty breathing, chest tightness, cannot keep their eyes open, and tears continuously, the concentration in the chicken house has reached 40–60 milligrams per kilogram. The latter two levels exceed the prescribed standard, and ventilation should be started immediately.
(3) Peracetic acid treatment: To prevent ammonia poisoning in chickens, spray with 0.1%–0.2% peracetic acid 2 times per week, using 30 milliliters per cubic meter of poultry house. The smaller the droplets, the better. Avoid spraying the chickens directly, and spray all areas and corners of the poultry house evenly.
(4) Add microbial preparations to the feed. This can effectively improve feed conversion and reduce the total amount of nitrogen-containing substances in the manure, thereby effectively reducing the amount of ammonia produced. The general inclusion rate is 0.5%–1%.
(5) Treat manure with phosphate fertilizer. Spread phosphate fertilizer (superphosphate) in the poultry house to reduce ammonia production. Generally, spread about 0.5 kilograms of phosphate fertilizer per square meter, 1 times per week.
(6) Prevent and control intestinal diseases. Prevent diseases that disrupt digestive function, such as coccidiosis, enteritis, and pullorum disease in chickens.
(7) Add plants of the genus Yucca to the feed. During seasons when ammonia problems are common, where feasible, add the yucca plant Yucca schidigera to broiler and layer feed to help inhibit ammonia release.
[Treatment methods]
(1) Open doors and windows or run fans for ventilation. If chickens show symptoms of ammonia poisoning, immediately open the doors, windows, air vents, and exhaust fans to ventilate the poultry house. Remove manure and litter, and spread plant ash on the floor. If possible, move the chickens to another poultry house with a better environment. To prevent the temperature in the poultry house from dropping too much during ventilation, it is recommended to take measures to raise the temperature and ensure that it remains suitable for the flock. Spray the walls and ceiling with 0.3% peracetic acid, disinfect 1 times a day, and after 2 consecutive days, reduce this to 1 times every 2 days to neutralize ammonia. After 1 weeks, resume routine disinfection using other products that can be used while chickens are present.
(2) Symptomatic treatment: For severely affected chickens, administer 1% dilute acetic acid orally by drench, 5–10 milliliters per bird; wash with a 1% boric acid solution, provide 5% glucose water to drink, and administer vitamin C powder orally. In addition, increase the amount of multivitamins added to the feed, add kanamycin sulfate to the drinking water, or use other antibiotics in the feed to prevent secondary respiratory diseases.