Tiger Feeds highlights ascites as an economic challenge

by Given Hamnungu, Tiger Feeds Livestock Technical Advisor

Ascites is not a disease, but a multi-factorial syndrome caused by interaction between genetic, physiological, environmental and management factors. It is a metabolic disorder characterised by an increased workload of the cardiopulmonary system (hypoxaemia), an accumulation of fluid in the abdominal cavity, hypertrophy of the right ventricles and a flaccid heart, all of which often lead to death. It has become a major concern to the poultry industry around the world. This condition is extremely common at high altitudes and more particularly during winter or cooler seasons. Ascites develops gradually and the birds suffer for an extended period before they die. The underlying factor to the development of these symptoms is an insufficient oxygen supply to the tissues of a rapidly growing broiler. Mainly environmental factors associated with management practices contribute to the development of the syndrome. Broilers which are susceptible to ascites showed a reduced function of the tissue mitochondria. Environmental factors, which increase the demand for oxygen, such as low brooding temperature, or which impair oxygen supply to the blood, such as high altitude, are known to increase the incidence of ascites.

Causes of ascites

Today's broilers grow much faster and eat less feed. 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 demands more oxygen, requiring more work from the heart and lungs. Anything that limits oxygen uptake from the lungs is going to cause the heart to work harder. Therefore, the main cause of ascites is poor ventilation in poultry houses, resulting into the following: Presence of ammonia in the poultry house. Birds are unable to get adequate oxygen as they inhale air full of ammonia, so their blood is deprived of an oxygen supply.

Closing curtains of the poultry house increases toxic air and reduces oxy

The dust particles in the air of poultry sheds are inhaled by the birds and while exhaling they settle in various part of their air sacs, especially the thoracic air sac where air stays for a longer period, which leads to difficulty for birds to breath, hence the deficiency of oxygen in the blood. Presence of high carbon dioxide levels in the shed, either due to overcrowding, poor ventilation, blocking of fresh and cold air during winter with curtains or due to the lack of proper exhaust fans resulting in the deficiency of oxygen in the blood of the birds. High altitudes have also been long known to cause heart failure and ascites.

Environmental factors Cold temperatures

Cold exposure is the most important secondary factor that causes ascites syndrome in broilers raised in open sided and non-insulated poultry pens that has a lasting effect on the incidence. When the ambient temperature is relatively lower than the bird’s body temperature, there is a sharp increase in oxygen consumption. Exposure to cold periods that place the birds outside their thermo-neutral zones will increase the demand for oxygen as this will force the birds to generate more energy to keep warm.

Brooding temperature Genetic factors

Broiler chickens have been selected for a higher growth rate; therefore more oxygen is required to sustain the rapid growth. The time required to reach 1,5 kg live weight has been reduced from 120 days in 1925 to 30 days in 2005. The capacity of the lungs to pump oxygen to meet this rapid growth rate is inadequate as they grow less rapidly than the rest of the body.

Management

High nutrient density rations and high feed intake are necessary for a bird to grow faster and cannot be ignored. Therefore, if the correct management practices are not followed, it can have a devastating effect on birds by causing ascites syndrome.

Signs of ascites:

A high rate of panting is often observed in ascitic birds, even with the absence of apparent heat stress. Gurgling sounds often accompany panting. Ascitic birds may show signs of cyanosis (a blue discolouration of skin), especially around the comb and wattles. Ascitic birds tire out easily and often die on their bellies. Most deaths begin at about three weeks of age. If their bellies are opened, a cup or more of fluid or jellied material will pour out. Lungs of ascitic bird may often appear pale or greyish. Lungs are extremely congested and oedematose. Liver enlargement is often seen.

For more information, contact Rowena Blanco at +260- 96-7991-847 or +260-96- 7790-404, send an e-mail to rowena@tigerfeeds.com.zm, or visit the website at

www.tigerfeeds.com. gen levels.