Ascites in Chickens | Water Belly

Ascites in chickens, commonly referred to as water belly, represents a spectrum of physiological and metabolic changes leading to the excess accumulation of fluid in abdominal cavity. These changes occur in response to a number of dietary, environmental and genetic factors.

The term ”ascites” actually refers to the fluid accumulation in abdominal cavity: so-called “water belly”. The disease is more scientifically known as pulmonary hypertension syndrome. Ascites is most commonly diagnosed at 4 to 5 weeks of age. Total mortality due to ascites is higher in the male parent lines, which have the capability of faster growth and higher muscle deposition compared to the female lines (Dewil et al., 1996).

The pathology is associated with abnormally high blood pressure between the heart and lungs (pulmonary hypertension) leading to heart failure, increased blood pressure in the veins, and excessive build-up of fluid in the liver which leaks into body cavity (Maxwell, 1990).

Endotoxins

A considerable number of ascites syndrome in broiler flocks is caused by microorganisms. Most of the Gram-negative bacteria (E. coli, Salmonella sp., Campylobacter) are considered pathogenic because of their lipopolysaccharide (LPS) layer. 

Some studies have shown that LPS triggers pulmonary vasoconstriction leading to ascites (pulmonary hypertension) in broilers (Chapman et al., 2005). Airborne LPS is ubiquitous in the environment of broilers, and is positively related to the amount of organic dust in poultry houses (Zucker et al., 2000).

For example, respiratory exposure to E. coli can amplify the incidence of ascites five-fold in broilers. It is known that Salmonella typhiumurium may cause up to 79% mortality in one week old chickens. However, in some studies lesions of salmonellosis were reported for 4 to 6 week old broilers with E. coli co-infection consequentially leading to ascites (Ganapathy et al., 2000).

Firstly, it is important to understand the underlying causes of an ascites occurrence on a poultry farm. In the case of ascites caused by genetics, feed restriction might reduce the effect of the disease. Slower growing birds have reduced oxygen needs allowing the cardiopulmonary organs (heart and lungs) to keep up with oxygen demands of the birds.

However, reducing feed intake decreases broiler growth performance. Feed restriction is only of economic benefit when the incidence of ascites is very severe.

In the case of ascites caused by microorganisms, recent studies investigating the effect of feed supplementation with acidifiers have shown promising results. Of course, optimal management practices are also very important for reducing the problem of ascites and maximising performance of broilers.

Improvements in growth performance and decreases in mortality rates, as well as benefits in alleviating ascites in chickens have been observed in recent trials with BIOMIN’s acidifier product Biotronic® SE.

Ascites incidence

Ascites incidence was characterized by clinical signs (panting, gurgling sounds, cyanotic combs and wattles, excessive abdominal fluid accumulation) and mortality rates. The incidence of ascites in chickens was confirmed by postmortem examination.

Results

For the initial 42 days, the broilers did not show any obvious clinical signs of ascites, even though on Day 35 mortality rates were recorded in the Negative control, Positive control and Biotronic® SE groups as 2.04, 3.09 and 2.39% respectively (Table 1). On Day 42 an outbreak of ascites was observed on the broiler farm with typical ascitic symptoms such as gasping, cyanotic combs and wattles, depression, extended abdomens, and increased mortality rates up to 7.53, 5.26 and 3.81% in the Negative control, Positive control and Biotronic® SE groups respectively. In the Biotronic® SE group, the mortality rate increased 37.27% over the mortality rate prior to the ascites outbreak, compared to 72.90 and 41.25% respectively in the Negative control and Positive control groups.