Majority of commercial broilers are reared in Nairobi and its peri-urban satellite areas of Kiambu, Limuru, Ngong, Ongata Rongai, Kitengela and Ruai. At this time of the year, these areas experience very cold temperatures, some as low as 20 degrees Celsius at night making brooding expenses escalate to as high as Sh12 per bird. The most predominant condition associated with this low temperature in fast growing broilers is a condition called ascites, where there is accumulation of fluid in the abdomen at 21-28 days of age. It’s also referred to as ‘water belly’.
Causes of water belly
Broilers by their nature are fast growing birds. They can double their day-old weight by day four and by day seven, they will weigh four times the placement weight. Water belly condition occurs when the heart is unable to pump enough blood through the lungs (pulmonary). This then creates back-up pressure (hypertension) from the lungs, through the heart, liver, and blood vessels especially around the intestines. This pressure results in fluid being squeezed out of the veins into the abdominal cavity creating ‘water belly’.
This condition is also referred to as pulmonary hypertension. If birds are reared properly and organs are fully developed, the heart can accommodate any pressure, and rarely do you see birds succumbing to hypertension. However, an excessive increase in demand for oxygen coupled with myriad errors that farmers make during the cold season can exacerbate the condition. The following situations will cause an increase in oxygen demand and tilt the heart into pulmonary hypertension.
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Cold weather
Fully feathered birds can comfortably regulate their body temperatures and generate internal heat to keep warm. However, if temperatures fall below 21 degrees celsius, there is an upsurge in oxygen demand leading to water belly.
Fluctuating brooding temperature
Birds can withstand a constant low temperature and adjust accordingly. However, they are extremely sensitive to fluctuating temperatures. Rise and drops of 3 degrees celsius can cause an increase in oxygen demand. If day temperatures rise to 27 and drop to 16 degrees in the night, it is disaster to young birds.
Poor air quality
If the chicken house has excessive ammonia, or extremely dusty air, the lungs will have a problem getting enough oxygen. This net demand of the same will lead to ascites. In extreme cases of ammonia, the lung tissues get damaged and result into increase demands. Ammonia levels should be kept below 10 ppm always.
Excessive carbon dioxide
In addition to the correct temperature, ventilation needs to be considered. Ventilation distributes heat throughout the house and maintains good air quality in the brooding area and expels any accumulated carbon dioxide. During cold season, farmers tend to close the units diminishing the supply of oxygen, which can trigger ascites.
Stress
Managers or poultry attendants must be well conversant with the flock or individual birds’ requirement and be ready to offer responsive management actions that will reduce stress. The following stressors will lead to higher oxygen demand as the birds struggle to cope with unusual occurrences. These include high stocking density, inadequate ventilation, extremely bright lighting, inadequate feed and water supply, sub-optimal nutrition, poor health and welfare issues. These will ultimately trigger ascites in fast growing birds.
Solution to water belly
During the cold weather, it is imperative that brooding temperatures are constantly monitored and should never to go below 21 degrees celsius. Supplement more burners in the unit if need be. Maintain minimum ventilation in the poultry unit throughout the rearing and finishing phases. Do not cover the units with impermeable curtains like plastic in the guise of reducing cost of brooding, as ascites kills big birds that have taken quite a chunk of your feed.
Keep your litter dry all the time to minimise ammonia build up. Remember, good air quality will lead to less damage of lung tissues that are important for oxygen exchange.
It’s important to reduce stress to birds during the cold season. Ensure feed and water are available all the time, reduce light intensity to level of one candle light, and walk the birds at least twice per day in the unit. Boost diet with supplementary vitamins and minerals during this period. [vet@kenchic.com]
