Ascites in Broiler Chickens

Ascites (or water belly) is a condition of fast growing broiler chickens in which the excess amount of ascitic fluid accumulated in the abdominal cavity. It has become major concern to the poultry industry around the world. This condition is extremely common in high altitude & more particularly during winter / cooler season.

Ascites is associated with inadequate supply of oxygen, poor ventilation and respiratory disease complex aetiology. Morbidity is usually 1-5%, mortality 1-2% but can be up-to 30% at high altitude.

During winter season broilers are fed high energy diets to meet their nutritional demands. Since fast growing broilers have high basal metabolic rate (BMR), to metabolize high energy diet, their body needs of oxygen multipliers. There is high demand of blood through heart & lungs for proper body function due to high BMR & high energy diet.

This physiological demand increase pulmonary arterial pressure (hypertension). Bird lungs have very little ability to expand and the blood capillaries in the lungs are not able to handle increased blood flow or blood pressure. The result is an increased pressure in the liver with leakage of blood fluids, without the red blood cells, into the body cavity forming ascites or water belly.

Following may be the cause of ascites (water belly):

Today´s broilers grow much faster, eating less feed. The growth of the heart and lungs has not increased in size proportional to the increase in body weight and breast meat yield. The rapid growth of the bird means more oxygen demand, requiring more work out of the heart and lungs.
Anything that limits oxygen uptake from the lungs is going to cause the heart to work harder. Diseases of the lungs and poor ventilation may be involved. Major cause of Oxygen deficiency :

a) Presence of ammonia in the poultry house. Birds are unable to get adequate oxygen as they inhale air full of ammonia so blood is deprived of oxygen supply.

b) The dust particle in the air of poultry shed are inhaled by the birds and while exhaling they settle in various part of air sacs, specially thoracic air sac where air stays for longer period which leads difficulty for birds to breath hence deficiency of oxygen in the blood.

c) Presence of high carbon dioxide level in the shed either due to overcrowding, poor ventilation, blocking fresh & cold air during winter with curtains or due to lack of proper exhaust fans results deficiency of oxygen in the blood of bird.

Excess levels of sodium in the water or salt in feed leads to increased blood pressure in the lungs. Many feed millers still use fish meal high levels of sodium. Levels of sodium over 400 ppm could cause problems in broilers.
High altitudes have long been known to cause heart failure and ascites.
Chilling is a common cause in small flocks. It causes an increased blood flow through the lungs.

Signs of ascites:

High rate of panting is often observed in ascitic birds even the absence of apparent heat stress.
Gurgling sound often accompany as they often just sit with panting.
Birds which are ascitic may show sign of Cyanosis (a blue discolouration of skin) especially around comb & wattles.
Ascitic birds tire out easy and often die on their bellies.
Most death begins at about 3 weeks of age.
If their belly is opened, a cup or more of fluid or jellied material will pour out.
Lungs of ascitic bird may often appear pale or greyish. Lungs are extremely congested & oedematous.
Liver enlargement is often seen.
Thickening of right side myocardium & dilation of the ventricle are very common.
Microscopic finding - increased cartilage nodules in lung.
Sometimes birds die from the effects of too much blood and fluid in their lungs before there is any significant amount of fluid in the body cavity.

Identification:

To differentiate from broiler "Sudden Death Syndrome" and "Bacterial Endocarditis", a cardiac specimen (Troponon T) can be measured in blood.

How to minimize ascites (water belly)?

Keep air quality fresh by moving air regularly and efficiently. In the colder months, it is better to add heat and keep the air moving than to shut down vents or reduce airflow in an effort to conserve heat.
Treat litter by "Liiteron" to reduce ammonia production. Litter treatment is important to reduce incidence of water belly.
Restricting feed, feeding a mash diet, or using a less energy and protein diet.
Checking sodium level of water, if sodium level is high then consider using an alternate source of water that is better quality for the first 3 - 4 weeks.
Replace fish meals with other readymade source like amino acid arginine, if it is being used as Sodium level more than 400 ppm could be problem for broiler.
Careful attention to brooding temperature is also critical for minimizing water belly.
Prevent respiratory disease conditions.
Select breeds which are not genetically susceptible to this condition.

The objective should be to minimize progression leading from pulmonary hypertension to terminal ascitis or water belly condition for availing better profit during winter season. Best Management Practice is only answer to reduce problem of Ascites (Water belly) and insure better ROI.