The losses resulting from ascites can overlap with another metabolic condition known as sudden death syndrome (SDS). In both cases, the cardiovascular system is central to the issue.

In the case of sudden death, there is a sudden heart failure, but in the case of ascites, the bird dies due to right ventricular failure that develops over time.

The mortality rate resulting from ascites ranges from 3-5%, but it can reach around 12% or more in some countries.

The cause of ascites seems to lie in a lack of oxygen. Some factors, such as high altitudes, poor ventilation, large temperature fluctuations, respiratory diseases, and rapid growth, also contribute to reducing the available oxygen. When oxygen is low or limited, the body produces a greater amount of hemoglobin and red blood cells, which leads to increased blood viscosity. This results in elevated blood pressure and increased resistance to blood flow, causing increased workload on the right ventricle that pumps blood from the lungs. Over time, the right ventricle enlarges, leading to fluid leakage from internal organs like the liver. This fluid accumulates in the body cavities, which is where the term "ascites" or "abdominal dropsy" comes from.

There is a relationship between nutrition and ascites concerning decreased calcium absorption and the potential accumulation of lactic acid. Since regular ground feed is more likely to produce a larger amount of lactic acid in the proventriculus, pelleted feed should prevent the occurrence of ascites but may increase mortality due to sudden death syndrome (SDS).

Certain strains of yeast can enhance the utilization of lactic acid or lactates by bacteria, which can help reduce its accumulation. Environmental stressors, such as significant temperature fluctuations or high ammonia levels, predispose birds to the development of ascites. These environmental factors can often have a more pronounced effect on the incidence of the disease than nutritional factors.

When multiple predisposing factors occur simultaneously, the risk of ascites increases. Even if birds remain alive until market age, they may die during transport to the slaughterhouse due to low oxygen levels in the transporting truck. Birds that survive but are affected by the disease may be rejected on the slaughter and processing line due to the presence of fluids in body cavities or fibrinous lesions on the liver.

Several nutritional techniques have been employed to reduce the incidence of ascites. One effective strategy is to limit energy intake by carefully controlling the amount of feed given during the first 21 days, which may lead to slower growth but can also reduce the occurrence of the condition.

To this end, feeding a regular ground feed instead of pelleted feed during this period, limiting feed availability, or using a lighting program to reduce feeding times can help decrease feed intake.

Additionally, high levels of sodium and water in the feed can promote the development of ascites, so monitoring sodium levels is crucial. The feed should be thoroughly examined to ensure sodium levels are as close to expected values as possible.

The type of fat added to the diet is also important, as unrefined or oxidized fats tend to contribute to the onset of ascites. During periods of oxygen deficiency, there is an increase in free radical production and a higher demand on antioxidant status, which can exacerbate the condition.

Overall, a combination of proper feed management and nutritional strategies can significantly help in preventing ascites in poultry.

Birds suffering from ascites have high levels of lipoperoxidase. In addition to feeding antioxidants, it is important to ensure that the levels of Vitamin E and selenium in the feed are well controlled. A recent study showed that there is a good benefit from feeding selenium in its organic form to prevent the occurrence of ascites (Gones and Stanler, 2000). Adding high levels of Vitamin E (250 parts per million) combined with organic selenium was effective in reducing ascites (Roch and Boulianne, 2000). It is also very important to ensure a balanced amino acid profile while limiting excess protein in the diet when addressing the issue of ascites. This is because excess nitrogen must be removed from the body, which requires oxygen. A bird fed a diet with 24% protein instead of 20% protein easily needs about an 8% increase in the required oxygen (Leeson and Summers, 1997). Increasing protein can be costly for several reasons, especially since excess protein requires deamination.

The use of ammonia removers, such as yucca extract derived from the yucca plant, has led to a reduction in cases of ascites.

Good ventilation at the beginning of chicks' lives is very important.

The level of ammonia increases if the bedding becomes wet or damp. If relative humidity can be controlled, it will reduce problems related to ascites. Bedding treatment is ineffective if the treated bedding is moist. It’s important to keep ammonia levels below 25 parts per million at the bird level. Yucca preparations have shown a significant effect in reducing ammonia levels in the small intestine when added at a rate of 125 parts per million or more.

There is a close relationship between the occurrence of ascites and the concentration of ammonia in the small intestine

There is a close relationship between the occurrence of ascites and the concentration of ammonia in the small intestine (Walkers, 1994). The production of uric acid requires five molecules of oxygen to produce one molecule of uric acid, so any increase in protein should be avoided. Studies have shown that muscle or meat production requires more oxygen than fatty tissue, which adds additional stress on modern poultry.

Field and academic research has indicated that feeding yucca extract at a rate of 125 parts per million is the ideal level to alleviate ascites (USDA, 1992). Higher levels (250 and 500 parts per million) offer some additional protection but are not sufficient to ensure their use. It is well-known that using yucca compounds or extracts can reduce the incidence of ascites by up to 35-40%. Additionally, there are significant benefits in terms of improved bird survival rates (lower mortality), as well as enhanced growth and feed efficiency.

These extracts act as inhibitors of urease, reducing both urease activity and ammonia content in the small and large intestines. This, in turn, results in a thinner intestinal wall, which should increase nutrient absorption.

There has been a reduction in cases of ascites when birds are fed zinc and manganese complexes along with amino acids. Additionally, there was a decrease in overall mortality rates, as well as in mortality specifically due to ascites. Some studies have shown a reduction in ascites-related mortality from 16.5% to 9.85%.

The use of these dietary additives led to significant benefits, including improved feed conversion ratios and increased weight gain compared to traditional feeding regimens. Other issues, such as slow feathering and inflammatory conditions, tend to respond better to mineral complexes, so these factors should be taken into consideration when formulating diets.