The Sunday News
Farming issues with Mhlupheki Dube
THERE is a disease which seems to be increasing in incidences especially among poultry producers. This is commonly called the water belly or ascites. It occurs in fast-growing meat birds.
You will notice that broilers are now growing even faster reaching maturity at six weeks when previously they would mature at eight weeks.
Ascites syndrome is a type of congestive heart failure seen mainly in young rapidly growing meat type chickens.
Ascites is an accumulation of protein rich fluid in the body cavity and because of the high protein level, there may be clots of yellow jelly-like material in the body cavity.
The accumulation of the fluid gives it the common name, water belly. The physiological explanation for the condition is that when the bird experiences high demand of oxygenate due to fast growth or poor ventilation the heart responds by increasing pumping of blood to the lungs for oxygenation. If the pressure remains high the muscle of the heart continues to thicken until the valve is no longer able to completely close. This causes blood pressure to rise in the veins especially from the liver. The result is an increased pressure in the liver with leakage of blood fluids into the body cavity forming ascites.
The main causes of ascites are that the genetics of meat birds has changed a lot in recent years. Broilers now grow much faster. 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 and predisposes the birds to ascites. Also diseases of the lungs and poor ventilation may also be a cause for ascites. Excess levels of sodium in water or salt in feed leads to increased blood pressure in the lungs with the same results. Again high altitudes have long been known to cause heart failure and ascites but that cannot be the cause in our case because we do not have very high altitudes like other parts of the world. Very cold temperatures may also cause ascites in small flocks due to an increased blood flow through the lungs.
Common signs of ascites in broilers are that their flesh tends to look bluish (cyanosis) because of inadequate oxygen in the blood, sudden deaths in rapidly developing birds. The birds have trouble breathing and often just sit and pant (dyspnoea).
They tire out easily and often die on their bellies (recumbency). There is also poor development and progressive weakness and abdominal distension in birds. When it occurs within the first week of life it is probably due to too much salt in feed or water.
Due to the fact that heart failure takes time to develop, most deaths begin at about three up to five weeks of age. Birds that die from ascites are recognised by a cup or more of fluid or jellied material pouring out of the belly cavity. Sometimes birds with the condition 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.
Ascites can be controlled by slowing the growth rate of the birds to reduce oxygen requirements through restricting feed and using low energy and protein diet. Also you can make sure there is adequate ventilation for your birds while at the same time preventing excessive cold temperatures which can cause chilling of your birds especially during the first week. Ascites can cause mortality to be as high as 10 percent in your flock and this means you are already making a loss. I know a farmer who lost 18 birds in five days from a small flock of just 50 birds. You can do the gross margin estimates and the answer is described by one word, loss! Uyabonga umntakaMaKhumalo.
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