Ascites (or water belly) is a condition of fast-growing broiler chickens (especially in male broilers) in which the excess amount of ascetic fluid isaccumulated in the abdominal cavity. It has become amajor concern to the broiler producers around the world.
Causal factors
Genetics, environment, and nutrition all seem to interact to produce ascites syndrome. The high metabolic rate of current broiler lines causes an increased demand for oxygen, especially in cold environments or when birds are fed high nutrient density diets. The first 3 weeks of a bird’s life are metabolically stressful as bone and muscle growth are greatest at this time (especially male broilers).
Nutritional and Management strategies
As the fast growth is a major factor contributing to the susceptibility of broilers to ascites, early-age feed or nutrient restriction (qualitative or quantitative) in order to slow down the growth rate seem practically viable methods, since final body weight is not compromised.A reduced growth rate from 3 to 21 days of ages not only benefits bird health during that period but also later when the growth rate is as fast. Many nutritional and management strategies have been proposed to alleviate the problem.
- Reducing the dietary level of salt (NaCl) and adding bicarbonates to the diet have been proposed as potential cost-effective methods to reduce ascites incidence. The addition of 1 to 1.5% ofsodium bicarbonate to the diets of broilers has decreased mortality due to ascites.
- Increasing thedietary arginine level has significantly reduced the mortality caused by ascites.
- The combined use of higher dietary levels of vitamin E and organic selenium (250 IU vitamin E and 0.3 ppm selenium yeast) significantly reduced the mortality caused by ascites.
- Birds fed on an ad libitum low-nutrient density regimen (2900 kcal,and all amino acids level to be maintained in relation to energy levelfrom 3-21 day) showed significantly reduced ascites mortality compared with the birds fed ad libitum with a high-nutrient density regimen (3000- 3100 kcal, and all amino acids level to be maintained in relation to energy level from 3-21 day).
- Quantitative feed restriction has proven successful in reducing ascites especially in summer: feeding the birds only in the morning and late evening (cooler part of the day) and withdrawing feeders during the afternoon (hottest part of the day).
- Most meat birds are fed crumbled or pelleted diets to achieve maximum growth and feed efficiency. Feeding mash reduces growth rate (1 to 2 days to market), and ascites. However, this type of programme may not be economically acceptable in all areas and has been demonstrated to increase the incidence of pendulous crops.
- Manipulation of the early growth cycle of broilers, with a subsequent compensatory gain, seems a practical and viable method to minimize losses caused by ascites (especially in male broilers).Birds whose growth is controlled early may have a stronger cardiovascular system going into the finisher phase.
Cold temperature
Strong correlation between cold temperature and ascites has been recognized. Cold temperatures increase ascites by increasing both metabolic oxygen requirements and pulmonary hypertension. Adequate temperature control of the house may reduce the incidence of ascites.
Ventilation
It has been suggested that poor ventilation could cause low environmental oxygen or high toxic fumes (carbon monoxide, carbon dioxide or ammonia), which may have detrimental effects on the respiratory or cardiovascular systems of birds and promote ascites development. Good air movement and litter management may reduce the incidence of ascites.
Conclusions
Ascites is a multifactorial syndrome, caused by interactions among environmental, nutritional and genetic factors. Nutritional practices to limit growth rate in the early stage by feed restriction, feeding lower nutrient density dietand diet in the form of(pellet vs mash)have beenfound to be beneficial. Adequate temperature control of the house, good air, litter management, and reduced sodium in feed will reduce the mortality due to ascites (especially in male broilers).
by Prof. G. Devegowda
