Urolithiasis in chickens

Urolithiasis in chickens is formation of urinary calculi in the urinary tract, mainly kidneys. The

condition is characterized by gout in the kidneys and abdominal organs, marked reduction in the size

of one or both kidneys (atrophy) and distended ureters, often containing calculi (uroliths).
In recent

years, outbreaks of mortality in the laying hens have been caused by urolithiasis. Urinary calculi may cause sudden death by plugging ureters. However, this is secondary to kidney damage. Urolithiasis is primarily a disease of laying flocks.

Causes

I. Kidney damage.

2. Excess dietary calcium, particularly if associated with low available dietary phosphorus fed to growers.

3. Infection with infectious bronchitis virus (nephrotropic strains).

4. Water deprivation.

5. Certain mycotoxins which damage kidneys, such as ochratoxin and oosporein.

Symptoms

Mortality in affected flocks may exceed 20% for several months. In severe cases, it may exceed 50%. Laying hens die suddenly and may be in good condition and in full lay. Or, they may have small pale combs, and white pasting on feathers surrounding cloaca.

Postmortem Findings

I. Kidneys show diffuse urate deposits, and may be greatly swollen (Fig. I 19, 120, 121).

2. Kidneys may be atrophied and ureters dilated.

The dilated ureters often contain white irregular urinary calculi. These calculi are composed of compact masses to fine crystals of calcium sodium urate.

Diagnosis

Urolithiasis can be diagnosed from the typical postmortem finding of renal gout (kidney gout).

Treatment

Dietary acidification with ammonium chloride, ammonium sulphate, or methionine decreases incidence of urinary calculi and improves condition of the kidneys. However, use of ammonia chloride is not a practical treatment because it causes increased water consumption, urine flow, and faeces moisture. Ammonium sulphate is more effective than two forms of methionine.

Control

I. Ensure availability of adequate water.

2. Control mycotoxicosis by adding toxin binders in the feed.