Fact: Having many chickens in one coop makes abrasions in their mucus membranes and respiratory tracts, and is overall bad for their health. — Joel Salatin, Farmer/Author, Polyface Farms.
TRUE: Chickens being in crowded conditions has adverse health impacts on chickens, such as facilitating the spread of disease.
John Glisson in his article, “Bacterial respiratory disease of poultry” (1998), cites two common diseases of poultry:
- Fowl cholera
- Infectious coryza
The first, fowl cholera, is mainly caused by a bacterium, Pasteurella multocida (PM). The disease multiplies in bloodstreams of birds. Vaccines are available, as are antibiotics. (tetracyclines and sulfonamides, penicillins, Fluoroquinolones) . Glisson writes, “various animals, particularly cats and rodents, are a common source for the introduction of the organism into commercial poultry” (1139).
The second disease, Infectious Coryza, is an upper respiratory infection. Glisson notes, “the infection does not spread readily from farm to farm without movement of contaminated people or fomites from farm to farm” (1140).
By outlining these two diseases found in poultry and how they spread, it becomes apparent that having many chickens in one coop can facilitate the spread of disease due to their close proximity.
Another disease threatening commercial poultry, Newcastle disease. In their piece, “Influence of poultry house dust, ammonia, and carbon dioxide on the resistance of chickens to Newcastle disease virus” (1966), Anderson, Beard, and Hanson examine how chicken coop air quality impacts the health of poultry.
They first set a baseline by writing, “[p]revious studies on ammonia inhalation in chickens (1) showed that 72 hr of exposure to atmospheric concentrations in the range of 20 to 50 parts per million (ppm) significantly increased the infection rate of chickens subsequently exposed to an aerosol of Newcastle disease virus (iNDV)” (177). This demonstrates how important air quality is to the health of poultry.
Then they conduct a trial experiment to identify the impact of poultry house dust, ammonia, and carbon dioxide on the resistance of chickens to iNDV, which is outlined below:
- Trial experiment
- One group exposed for 6 hours to the atmosphere with suspended dust and aerosol of iNDV
- Second group exposed to dust-laden atmosphere in the chamber for 2 hours a day for 8 consecutive days and exposed to aerosol of iNDV
- Third group placed in a metro pathology building with turkey flock. Dust carbon dioxide and ammonia concentrations present in meteropatholgy building during this 6 day exposure.
- Four group exposed to a combination of ammonia and carbon dioxide at the same concentration as the third
The results were mixed, but notable:
- “Because the concentration of dust in the air of a poultry house is dependent upon a number of variables such as relative humidity, litter moisture, ventilation rate, and population density, it is difficult to incriminate the dust alone as having an effect on the birds” (186).
- “Chickens exposed artificially to “poultry house dust” showed no gross or microscopic damage to the respiratory tract after 6 hr of continuous exposure or 2-hr exposures for 8 consecutive days. Chickens exposed “naturally” to ammonia, carbon dioxide, and dust in the environment of a poultry house for 6 days had some loss of cilia from the epithelium of the upper portion of the trachea and the turbinates” (187).
While there was little variance among the experiment groups, there was a noticeable negative health impact on the birds.
In summary, crowded chicken coops and exposure to poultry house dust has negative health impacts on chickens. And as previous studies showed, exposure to increased ammonia (which is found in chicken manure), can increase the rates of infectious disease found in chickens.
Anderson, D. P., C. W. Beard, and R. P. Hanson. “Influence of poultry house dust, ammonia, and carbon dioxide on the resistance of chickens to Newcastle disease virus.” Avian diseases 10.2 (1966): 177-188.
Glisson, John R. “Bacterial respiratory disease of poultry.” Poultry science 77.8 (1998): 1139-1142.