The internal environment of the barn directly affects the health of the birds and the expression of the productive parameters. For this reason, the farmer must know what type of gases and particles are in contact with the respiratory tract of the inhabitants of the barn and the operators, which can trigger swollen head syndrome in birds.

Four main environmental components found in farms

• Oxygen (O₂) 

It is necessary for the continuity of life. In the barns its optimum concentration must be 21%, since levels lower than 16% are harmful to health and below 6% are fatal. Poor oxygenation of the barn will cause related pulmonary problems, such as pulmonary hypertension, accumulation of fluids in the coelomic cavity, ascites and death due to heart failure. The availability of environmental oxygen must be considered, since farms located at high altitudes will have a lower partial pressure of oxygen, which, added to poor conditions in the barn environment, will lead to the mentioned problems.

• Ammonia (NH₃)

This gas is produced by the decomposition of the organic matter that composes the litter. This type of toxic and highly irritating gas decreases the quality of the air and directly affects the health of the birds and the workers that work inside the barn.

• Working with barns with concentrations lower than 20 ppm of ammonia allows obtaining expected production parameters.
• Concentrations higher than 20 ppm in the environment cause congestion of mucous membranes, ocular irritation, lacrimation, mucosal hypersecretion.
• Values of 50 ppm or more are dangerous and will affect growth.

Ammonia and its health risks should be measured in conjunction with other factors such as humidity and ventilation. Thus, environments with incorrect ventilation and relative humidity greater than 70% contribute to the formation and accumulation of environmental ammonia. High concentrations of ammonia produce bronchial constriction, hyperplasia of the bronchial and alveolar epithelium, increased secretion of goblet cell mucus.

• Carbon dioxide (CO₂)

Waste product of respiration and also from the bad combustion of stoves, its concentration is related to the density of birds, their weight and metabolic activity. This product of respiration is toxic in high concentrations and being denser than air accumulates at the height of the birds.

• Dust

Dust particles present in the environment have their origin in food, the desquamation of birds, bed and fecal matter among the most important and failure in ventilation increase their concentration. Dust contributes to the gases, favoring irritation and damage to the respiratory tract and inclines towards the appearance of diseases derived from an inhospitable environment for birds.

All these factors, added to the presence of environmental pathogens or failures in the immunity of the birds predispose to the appearance of irritations, inflammations and lesions of the nasal and ocular mucosa that facilitate the entry of isolated pathogens as the cause of the swollen head syndrome (SHS). We can name Escherichia coli, Avibacterium paragallinarum, and avian metapneumovirus, among others. It is necessary to perform a pathogenicity test to verify that the isolated microorganism is pathogenic.

Swollen Head Syndrome in poultry

This Swollen Head Syndrome (SHS) is characterized by the appearance of sneezing, rales, conjunctivitis, tear secretion and subcutaneous edema in the head region. If the conditions of the barn do not improve, the disease spreads rapidly to susceptible birds and develops a pneumonia process by the addition of new opportunistic pathogens.

The optimal management of the internal environment, mainly ventilation to dissipate the toxic gases product of animal metabolism (CO₂) and formation by wet beds with high concentration of organic matter (NH₃) helps reduce the risk of Swollen Head Syndrome.

A developed immune system with an effective response capacity against adverse conditions and environmental pathogens is another pillar for profitable production.

Natural additives composed of plant extracts, have been shown to have active ingredients that stimulate the immune system, improve the lymphocyte number, reduce mortality and improve productivity.

Its incorporation in feed is recommended to maintain a valuable level of active immune cells.