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Ascites, more commonly known as ‘water belly’, is a condition defined as the excess accumulation of fluid in the abdominal cavity. 

The incidence of ascites in broilers often increases in winter months, especially at high altitudes, and can result in reduced broiler performance, increased mortality, and reduced profits for growers. 

New nutritional research has shown by supporting the bird’s acid–base balance and improving the balance of oxygen demand and supply to tissue, we can reduce the impact of ascites on broiler growers and our industry. 

Preventing and reducing ascites

Causes of ascites

Ascites is caused by dietary and management factors that result in an imbalance in oxygen supply vs demand by tissues. To compensate for this, broilers are forced to increase the workload of the heart, causing increased pulmonary arterial pressure and, ultimately, right ventricular failure (RVF) and ascites. 

Predisposing factors for ascites

  • Low partial pressure of oxygen, usually at high altitudes (increased haematocrit)
  • High broiler growth rates (increased oxygen requirement)
  • Cold stress (increased oxygen requirement)
  • Respiratory diseases (reduced oxygen exchange)
  • Incubator temperature (higher temperature, smaller heart size)
  • Acid–base balance (reduced oxygen uptake by red blood cells)

Nutritional strategies

Amino acid supplementation

Arginine (Arg) is an essential amino acid for birds that cannot be synthesised by de novo routes, and birds are dependent on dietary supply. Increased supplementation of Arg reduces susceptibility to ascites since it acts as a pool from which endothelial cells obtain arginine for nitric oxide (NO) production. NO acts as an endogenous pulmonary vasodilator which reduces the occurrence and severity of ascites.

Mineral supplementation

New research has shown replacing iron sulphate with more bioavailable forms of iron in amino acid (AA) chelate form can consistently increase blood haemoglobin levels, improve oxygen concentrations in blood, and increase blood pH. This results in more oxygen delivery to tissues and is especially important in young broilers subject to cold stress or with high growth rates.

Optimise acid–base balance

Metabolic acidosis causes vasoconstriction, which affects pulmonary arterial pressure and pulmonary hypertension. Therefore, optimising diet acid–base balance by reducing dietary chloride and sulphate levels in feed can increase blood pH and thereby the oxygen carrying capacity of red blood cells via the Bohr effect.

Management practices

What does iron do?

Iron (Fe) is by far the most abundant trace element in the body. Approximately 60% of the body’s iron is present as haemoglobin, a complex of the protopotphyrin haem and globin. The haem molecule contains one atom of iron in the centre of its ring structure and there are four rings in each haemoglobin molecule. As oxyhaemoglobin, it carries oxygen from the lungs to the tissue.

Iron is widely present in animal feed ingredients. Unfortunately, its concentration and availability vary between and within the various sources. In ingredients of animal origin, iron is mostly found complexed to haemoglobin and myoglobin, whereas in plants it is mostly bound to phytate. In mineral ingredients, it may be found in the ferrous or ferric forms. Haem iron is absorbed preferentialy to inorganic iron. Supplementing broiler diets with Availa Fe improves the absorption of iron by the broiler as it is absorbed as an amino acid and not inorganic iron.

Zinpro® Availa® Fe 100

Reg. number: V21168

Zinpro Availa Fe (iron amino acid complex) is a nutritional feed ingredient for animals that contains organic iron. The trace mineral iron is required by animals for numerous functions, including oxygen transport, immunity, and muscle development. In addition, when an animal has the proper balance of trace minerals it is better able to cope with the challenging effects of stress.

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