Avian Gout/Kidney Failure
Avian gout is a consequence of kidney damage which can occur from a number of potential causes leading to the accumulation of uric acid/urates in the renal tubules and serous coats of the heart, the liver, the mesentery, the air sacs or the peritoneum.
Due to its complex etiology, avian gout is difficult to diagnose; however, the most common signs are dehydration, pale combs, depression and swelling and reddening of the feet which impair bird movement. In layers, where it is mainly observed, avian gout can lead to mortalities up to 50%, with 19-35 week-old hens most affected.
The causes of avian gout are varied (see table), ranging from management and/ or nutrition-related, to pathogens and/or the presence of mycotoxins in feed. In terms of nutrition, special attention must be paid to the calcium/phosphorus balance, sodium and vitamin D3. In general, any condition favoring an increase of uric acid in blood favors precipitation in tissue and, as a consequence, development of gout. Excess dietary calcium with low available phosphorus results in the precipitation of sodium-urate crystals and calcium pyrophosphate (pseudogout). In younger birds, gout due to sodium intoxication may be observed at sodium levels exceeding 0.4% in water and 0.8% in feed.
Likewise, high levels of vitamin D3 can increase calcium absorption from the intestine favoring the formation and deposition of urate crystals. Another nutrition-related cause is the protein level in feed which in excess of 30% causes uric acid production leading to excretory loads in kidneys. Concurrently, sulphates decrease calcium resorption causing excess calcium secretion through the urine. This favors gout, as well as any other factor contributing to urine alkalinity. Water deprivation falls in this category as it leads to increased concentrations of uric acid and other minerals in the blood and later on in the kidneys and urine.
Viruses such as infectious bursal disease (IBDV) and/or infectious bronchitis can enhance mortality in the presence of pre-existing kidney damage. In terms of mycotoxin contamination of poultry feeds, the nephrotoxic aflatoxins (Afla), ochratoxin A (OTA) and citrinin are of major concern. The impairment of the kidney function which results from the action of these mycotoxins reduces uric acid excretion and results in the accumulation of uric acid in the body.
Ochratoxin A (OTA), Citrinin, Aflatoxins (Afla)
Due to kidney damage, uric acid excretion is reduced resulting in the
|• Positive for OTA, citrinin or Afla in raw materials (ELISA) or feed (HPLC).|
• Raw materials originated from supplier/region with history of OTA contamination.
• Histopathology: Check other target organs of OTA and citrinin (e.g. kidneys).
• Overall decline in flock performance.
• Check average contamination levels.
• Add an effective mycotoxin deactivator in the feed.
• Prevent mold growth, purchase clean raw materials.
>30% of protein in feed causes uric acid production leading to excretory loads in kidneys. Concurrently sulphates decrease calcium resorption causing excessive calcium secretion through urine, which favors gout.
|Protein levels in feeds||• Correct protein levels in feeds.|
Excess Ca in chick diets
Precipitates in the kidney and surrounding tissues.
|Check feed formulation||• Ensure correct level of Ca in diet.|
Gout due to sodium intoxication at >0.4% in water and >0.8% in feed.
|Check water quality for salinity and feed formulation to maintain correct levels of salt.||• Ensure water and feed are safe.|
Excess Vitamin D
Increases Ca absorption from the blood.
|Check premix formulation|
• Correct level of minerals and vitamin D3 in diets.
• Control total sodium chloride content in feed (<0.3% ).
Infectious Bronchitis (IB) especially nephropathgenic strains (QX)
IBD is very immunosuppressive and leads to kidney damage.
|Maternal antibody titers are very low in day-old chicks.||• Adapt vaccination program to the demands of the field situation in each particular area/epidemiology.|
• Increase biosecurity level.
Infectious Bursal Disease (IBD)
IB causes respiratory disease and kidney damage in growers and oviduct infection in adults.
|Laboratory tests to confirm the presence of the coronavirus in a swab or tissue sample.||• Adapt vaccination program to the demands of the field situation in each particular area/epidemiology.|
Water deprivation leads to concentration of uric acid and other minerals in the blood and later in the kidneys.
|• Observe animal behavior to understand the cause of water deprivation.|
• Transportation and vaccination procedures.
• Drinkers in terms of number, position and blockages that may be impeding animals to access them.
• Chemicals added into water (disinfectants, copper sulphate, etc.) may result in water refusal, dehydration and gout.
• Improve transportation condition of birds (access to water).