Ascites in Broilers: Its Causes and Control

                                           Ways to Control the Incidence of Ascites in Broilers

In India especially in northern part the fluctuation in temperature varies from -1 degree to 48 degree Celsius, which is quite remarkable but for Broiler farming this presents a very big challenge. During winter season when temperature goes below 10 degree Celsius, temperature management at broiler farms becomes a very big challenge. Along with this if farmers were following improper management practices than birds suffer from stress & ultimately a challenge arises in front of broiler farmers called “Ascites syndrome”, which cause very heavy mortality and heavy economic losses.

Ascites has been first observed about 30 years ago at high altitudes in Latin America (in countries Colombia, Ecuador and Mexico) however, throughout the years, the syndrome has been found at lower altitudes and there is recent evidence that it is found at sea level as well. As per the recent data annual losses to poultry industry due to ascites all over world are as high as 100 Billion U.S. $. While in India mortality percentage going above 15 % is reported due to ascites especially in months having very low temperature. So there is emergent need to educate famers about the causes and remedies to control this ascites challenge. In comparison to broiler there are very few cases reported about ascites in layers or pullets.

What is Ascites and its causes

The term "ascites" actually refers to the fluid accumulated in the abdominal cavity (or "waterbelly") as a consequence of heart failure. This fluid generally accumulates in ventral hepatic, peritoneal or pericardial spaces and sometime also contains protein clots. There may be many predisposing factors but ultimately the final cause leading to ascites is deficiency of oxygen.

During winter most of the farms use curtains to maintain temperature, same time there is use of wood, coal and gas as material for producing heat inside. The burning of these materials resulted in production of gases such as carbon dioxide and carbon monoxide. During last decade or so there is tremendous improvement in genetic potential of bird to grow at a very rapid pace. To meet this genetic potential the quality of feed given to the broiler bird has also been improved to many fold and enriched with highly digestible amino acid and metabolizable energy. This type of feeding results in higher production of Ammonia from the feces. With closed curtains gases such

as CO₂, CO & NH₃ started accumulating inside the farm while O₂ concentration goes down.

During brooding stage the impact of this O₂ deficiency resulted in damage of air sac. As bird approaches 4^th week, the average growth rate goes up at rapid pace and the demand for oxygen also increase by many fold. Damaged air sac, closed curtains and high growth all combined together and hence birds not able to get the required amount of oxygen results in ascites syndrome.

In some cases due to temperature fluctuation or due to various stresses birds suffered from disease such as CRD or viral outbreak resulted in damage to respiratory system which hence could not able to support high demand of oxygen which again resulted in ascites

So going by these facts we can firmly confirm that broiler birds are vulnerable to ascites not only in winter but even during summer as well, although the incidence will be more during winter and especially in farms where there is improper ventilation & management.

Clinical Signs

A primary gross symptom shown in ascites includes a very high sudden mortality in fast growing birds, alongside there will be poor development with distention of abdominal region. Birds will show symptoms of respiratory distress and sometime they stretch their neck in response to lower O₂ level, while in some have lameness as well.

When birds are examined by doing post mortem examination the prominent symptoms observed like right side myocardium as well atrioventricular valve get thicken, dilation of the ventricle, Liver will be enlarged, congestion in lungs and intestine, congestion in veins as well muscle and ascitic fluid filled in cavity. So it’s quite easy to diagnose if birds get affected by ascites and as soon as the symptoms are visible it’s important to start preventive measures.

Treatment & Control

As been found out that growth rate is a key factor in the development of the ascites syndrome, so decreasing the growth rate of broilers by dietary manipulations is the first thing being suggested to control ascites. Diet mixed with grains such as maize, wheat can help in reducing the growth metabolism and hence will give time to the bird to recover. Same way use of Vitamin E and Selenium in the diet has been reported to have very good effect on controlling ascites issue. There are some additives available in the market which when used in the broiler diet help to control ammonia formation in the farm. But overall the best way to prevent ascites is by taking care of the management part at broiler farm especially ventilation because once birds get infected it become very tough to control. Few steps which can keep the broiler flock safe are mentioned as below

·         Maintaining a consistent temperature 

·         Keeping optimum air quality   

·         Keeping litter moisture level at low level, also if reusing litter then consider using a litter treatment.

·         By reducing stress in the flock

·         Keeping optimum flock density.

·         Making sure that feed is always available in feeder

·         Keeping adequate feed and water space.

·         Reducing light variation and keeping light levels at reasonable intensities

Some researchers have reported that feed restriction in the form of skip-a-day feeding programs have worked successfully to reduce mortality due to ascites syndrome. Although no depression in weight gain occurred when feed was restricted during the second week of life, feed restriction programs will result in depressed growth as high as 150 g/bird at 7 weeks of age.

Also supplementation of diet with Vitamin C has been reported to have beneficial effect if birds get affected with ascites.

Conclusion

So overall there is no available specific treatment for ascites syndrome. For broiler farmers one thing is quite necessary that they have to reduce stressors through any means. Some time it is difficult to focus on all the things at a time or correct all the management lapses completely but in such cases the best way is to take small steps towards improvement. As being taught that prevention is always better than cure, these words give a clear perfect message about what need to done to control this challenge.

Some farmer involve in broiler farming has habit of depending too heavily on treatment rather than following proper management, there are instances where birds are exposed to heavy antibiotics from day one to day of harvest. Such types of practices are totally wrong & one thing everybody needs to understand that there is no alternate of management practices in broiler farming. The disease such as ascites, gout, viral outbreak, coccidiosis and colibacillosis all are in most cases instigated due to faulty practices at farm and a small step towards improvement will definitely help to control these as well economic losses related with these.