Ascites or high altitude disease is caused by an imbalance between the demand and supply of oxygen to the tissues. If the demand is higher than the supply, the bird will try to pump more blood through the lungs towards the tissues, creating hypertension.

Several factors are influencing the occurence of ascites:

Housing:

- high alititude: oxygen availability at high altitudes is limited, which will increase the incidence of ascites.
- ventilation rate: limited ventilation will cause more ascites, as it will be more difficult for the bird to take up sufficient oxygen and release carbon dioxide
- heating system: if heater used which uses oxygen from the house or release carbon dioxide in the house, the supply of oxygen to the birds will be more restricted.
- ammonia: high levels of ammonia irritate the lungs and reduce the uptake of oxygen
- dust: it is found that high levels of dust in the air can induce ascites as well.

Metabolism:

- rapid growth rates will increase the demand for oxygen
- high energy diets will increase the growth and with it, the demand for oxygen
- high energy:protein ratio and pelleted diets will increase the growth and the demand for oxygen
- poor incubation and poor day old chick quality will limit the development of organs of the birds and with it, the supply of oxygen to the tissues
- basic metabolic rates: low temperature profiles will increase the demand of the bird to generate heat from feed and with it, increase the demand for oxygen

Management:

- reduction of feed intake, either quantitative or by light restriction, reduces the growth and with it, oxygen demand, thereby reduces ascites incidence.
- skip a day feeding or meal feeding will also reduce growth and with it, oxygen demand
- reduce stress in the flock, as stress will increase the demand for oxygen and with it, the blood flow through the lungs.