respiration

Chickens have nontidal respiratory systems, meaning that air passes through in one direction. First, air is inhaled at the nasal openings. The air then passes through the glottis and into the trachea. At the end of the trachea is the syrinx, which is further discussed under "Vocalization". Beyond that, the trachea divides into two bronchi, which each lead to their corresponding lung. Air can then pass through parabronchi that connect the lungs to multiple air sacs throughout the chicken's body (Jacob, 2021).

As stated by Dr. Jacquie Jacob from the University of Kentucky, "The key to the avian respiratory system is that air moves in and out through distention and compression of the air sacs, not the lungs" meaning that the lungs themselves do not inflate or deflate, it is the air sacs that participate in such activities (Jacob, 2021).

In total, a chicken has nine air sacs: two interclavicular, two abdominal, four thoracic, and one cervical. Other body structures that are important to maintaining proper air flow in respiration are pneumatic (hollow) bones (Jacob, 2021).

The respiratory system is involved with many bodily functions such as regulating body temperature, maintaining blood pH levels, and facillitating gas exchange of oxygen and carbon dioxide. But besides that, the respiratory system hosts a variety of microbiota.

A 2017 study gathered microbiota samples from nasal, lung, and buccal regions of chickens. The chickens were grouped by age: two days old, three weeks old, and thirty months old. The bacteria in the samples were identified using 16S rRNA gene analysis. The researchers found that the diversity of microbiota varied depending on where the sample was taken from (Glendinning et al, 2017).

As shown in the charts, each sampled region can host multiple kinds of bacteria at the same time. The quantity of those bacteria changes as the chicken gets older (Glendinning et al, 2017). The microbiota within the respiratory system is associated with the chicken's immune system, as chickens can be susceptible to respiratory diseases. Examples of respiratory diseases that can be fatal to poultry include Newcastle disease, Influenza, and Aspergillosis. Treatment for individual birds and entire flocks of birds is possible, but it is expensive and can be impractical (Wallner-Pendleton, 2016).

The author of the article formulated many equations in order to make calculations. They first found the rate of gas excretion, then the amount of total carbonate in the blood. Next, the conservations of carbon dioxide and oxygen was calculated. The Hill's Equation, as pictured above, was utilized to determine the saturdation of the blood. Lastly, a formula to measure the effect of time constant on ventilation was presented (Burger, 1980).

The article also discusses how carbon dioxide is more effective than oxygen in controlling ventilation. This is because oxygen is necessary for survival; it must be consumed frequently otherwise the organism's body will suffocate and be at risk of death. Oxygen is abundant in the atmosphere, and so chickens typically have a surplus of oxygen in their bodies. Carbon dioxide, however, must always be regulated in the body, so that blood and tissues do not become too acidic. Blood contains buffers such as hemoglobin, that help maintain carbon dioxide levels by transporting the carbon dioxide to the lungs, where it can then be exhaled. (Burger, 1980).