Urolithiasis in Sheep: Urinary Stones, Blockage and Emergency Care

Urolithiasis is the formation of mineral stones, also called urinary calculi, in the urinary tract. In sheep, the biggest danger is not the stone itself but the blockage it can cause when a stone lodges in the urethra and prevents urine from leaving the body. This is most common in males because their urethra is long and narrow, and it is especially common in wethers.

When urine cannot pass, the bladder becomes painfully overfilled. Pressure then affects the kidneys and the body’s electrolyte balance. As the blockage continues, a sheep may become depressed, stop eating, develop a swollen abdomen, or suffer bladder or urethral rupture. That is why this condition is treated as an emergency.

Stones in sheep are often linked to diet and water intake. High-phosphorus grain-heavy rations, mineral imbalance, and low water consumption all increase risk. Your vet can help confirm whether a urinary blockage is present and discuss which treatment path fits your sheep’s condition, welfare needs, and your goals for care.

Most cases develop from a mix of diet, anatomy, and water intake. Sheep fed high-concentrate or high-grain diets are at higher risk, especially when the calcium-to-phosphorus balance is off and phosphorus is too high. Low roughage intake, rapid diet changes, and feeds or forages with excess minerals can also contribute. In some regions, water or forage mineral content adds to the problem.

Male sheep are much more likely to obstruct than females because their urethra is narrower. Wethers are at particularly high risk. Early castration may contribute because the urethra has less time to fully develop, although nutrition and water management are still major drivers.

Reduced water intake is another common factor. Cold weather, dirty waterers, crowding, transport stress, or poor access to water can all lead to more concentrated urine. Some stone types are also influenced by urine pH, which is why your vet may discuss ration changes or urine-acidifying strategies such as ammonium chloride in selected cases.

Your vet usually starts with the history, diet review, and physical exam. They will look for signs of pain, bladder distension, dehydration, swelling around the sheath or belly, and whether any urine can be passed. In male sheep, the urethral process at the tip of the penis may be examined because stones can lodge there.

Diagnosis often includes bloodwork to check kidney values and electrolytes, especially potassium, because life-threatening abnormalities can develop with obstruction. Urinalysis may help assess urine pH, crystals, and blood, although crystals alone do not prove stones. Ultrasound is often very helpful to evaluate the bladder, kidneys, free fluid in the abdomen, and possible rupture.

In some cases, your vet may confirm the problem during sedation or a procedure to inspect the penis and urethral process. If a stone or gritty material is recovered, stone analysis can guide prevention later. That matters because long-term management depends on the likely stone type and the feeding program that led to it.

Prevention focuses on ration balance, water intake, and management of at-risk males. Diets should provide an appropriate calcium-to-phosphorus ratio, usually with more calcium than phosphorus, and avoid unnecessary grain loading. Forage should remain an important part of the ration. If your flock eats a concentrate-heavy diet, ask your vet or a ruminant nutritionist to review the full feeding program, including minerals, treats, byproducts, and pasture access.

Water access matters every day. Sheep should always have clean, fresh water that is easy to reach. Intake may drop in cold weather, during transport, or when waterers are dirty or crowded. In some situations, your vet may recommend adding salt to encourage drinking or using ammonium chloride in the ration to help acidify urine, but this should be done as part of a planned nutrition program rather than guesswork.

Management also matters. Wethers are at highest risk, and delaying castration until the urethra has had more time to develop may help in some systems. If one sheep develops stones, review the whole flock’s diet and watch closely for others showing early straining. Prevention is usually much more successful and less costly than emergency treatment.