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Disease that targets broilers in highlands

Broiler chicken feed under Smart Brooder in Tala, Machakos County, on June 27, 2018. [David Njaaga,Standard]

Dear Dr Messo

As broiler farmers in highlands, we face a lot of problems during the cold season. One of the challenges is waterbelly disease. Please advise on how we can control it. [Eunice Wairimu, Limuru]

Dear Wairimu, Waterbelly scientifically known as ascites is a common condition in a fast-growing breed of broilers reared in high altitude areas. It is also referred to as pulmonary hypertension. It is associated with cold seasons when farmers tend to compromise ventilation to conserve heat during brooding period.

How are ascites triggered?

Ascites happens when the heart fails to push sufficient blood through the lungs, hence increasing the blood pressure in the vessels supplying the heart, creating hypertension. Why do the lungs need more blood? Broilers by their nature of high growth rates, have extremely high demand for oxygen. The response to this demand is only satisfied by the heart increasingly pumping more blood to the lungs for oxygenation. Because the lung volume is fixed, there comes a time when they cannot accommodate more blood, then heart failure starts. Blood pressure will back up from the lungs, through the heart, back to the liver and abdominal organs. Heart and blood vessels will enlarge, and fluid will leak out and that is the source of all the extra ‘water’ seen in the abdomen of affected birds. What conditions cause ‘waterbelly’?

1.     Chilling or extremely low temperatures.

Low temperatures in the flock units as frequently seen during cold weather will increase oxygen demand to keep the birds warm. If temperatures go below 24 degrees centigrade in the brooding area due to failure to provide enough jiko or heaters, the birds tend to huddle together to generate more heat and, in the process, triggers more oxygen demand to keep warm. Chicks which are chilled on the first day of life will be stressed, dehydrated, have retarded growth and a higher incidence of ascites. Keep the units warm by making double-wall curtains, inside and outside the brooder. In extreme cases I recommend a false ceiling made of gunny bags to minimise loss of warm air. Temperature should be monitored by installing brooder thermometers at the height of the chicks but away from the heat source. Observe the chicks to determine if temperature is correct. Excessive chick noise shows that the chicks are uncomfortable.



2.     Poor air quality and compromised ventilation.

Any condition that affects the lung tissues or airways will result in low oxygen in the blood and hence increased cardiac output. Partially burnt charcoal will produce carbon monoxide which in turn reduces the oxygen-carrying capacity of the blood leading to high heartbeats and hence ascites. During cold season, always allow fresh air into the units even if it requires additional brooders in the chick comfort zone to avoid carbon monoxide poisoning. Always keep the units free of dustiness and ammonia gas.

Control of ascites

Where birds are growing very fast, one can slow the growth by giving mash diets at day 27-35. Where temperatures are low, introduce more heaters to prevent excessive body heat loss. Treat any respiratory disease early enough. Chicks also require fresh air to grow and be productive.  [The writer is head vet at Kenchic, watsonmesso@yahoo.com]



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