Obstructive urolithiasis in steers

Time and location: January 2020, northern Queensland.

Case definition: Young Brahman steers with a BCS of 2/5 became unwell, stand on their own, go into sternal recumbency and die within a couple of days. There was no sign of paddling prior to death.

Disease mapping: There were 1,200 steers in the paddock, some had been there for 18 months and others for 6 months. Cases were seen in both groups. While the paddock had ample water sources, all deaths were around a water trough used by about 200-300 of the steers. Cattle needed to walk 3-4 km from the water trough to feed, which was the longest walk for feed in the whole paddock. The windmill that filled the trough was not fully functioning and the trough was very slow to fill.

Gross findings: Three steers fell behind as the mob was mustered, walking with their heads down, tails extended and urine dribbling from their prepuce. The weakest was examined (revealing an enlarged bladder and hard, dry faeces) and euthanised. Post-mortem confirmed the bladder was extremely enlarged, the external surface was bruised and had macroscopic tears, and the internal surface had areas of grey-green discolouration. There was a urolith in the bladder and in the urethra. A full set of bloods, tissues, urine and the urinary calculus were sent to the laboratory.

Laboratory findings: Calcium carbonate stones with a trace of calcium oxalate. The urine pH was 9.

Animal / management / environment risk factors: Reduced water intake, urinary stasis, diet, high urine pH and urinary tract infection can predispose calculus formation. The water trough was slow to fill, and a large amount of white mineral had settled on the bottom of the holding tank. The lab commented that stones with a high carbonate content are associated with very alkaline urine and can occur in ruminants consuming high oxalate plants.

Recommendations to the producer: Perineal urethrostomy to prevent the bladder of affected animals tearing and rupturing is not practical in this case. To prevent further losses:

• Move the cattle on this water point to another paddock.
• Place female cattle in the paddock. Explore avenues to improve water quality and quantity.
• Where possible ensure cattle are walking no further than 2.5km to feed from a water source.
• Clean out the mineral deposit from the holding tank and repair the windmill/pump to ensure  adequate water supply.
• Test water for pH and minerals (including Na, P, CA).

Above: Enlarged bladder, external wall has tears and bruising; Internal surface has petechial heamorrhage and green patches (necrosis); Urolith lodged in the urethra at the caudal end of the os penis.