What is urinary calculi and how can I prevent it?


Urinary calculi (UC; also called “water belly” or stones) is a common problem in small ruminants, especially pet, dwarf, or show wethers, It involves the formation of calculi or stones (usually comprised of phosphate salts) in the urinary tract, which prevents the flow of urine. Left untreated, these blockages can cause the bladder to burst, resulting in death.

Urinary calculi affects mostly wethers (castrates), sometimes intact males, rarely females. Males have a longer, curvier urethra that makes it more difficult to pass calculi. Wethers are considered to be at higher risk than intact males because their urethras are smaller in diameter. Some believe that early castration (<3 months) further increases the risk in wethers because their urethras are even narrower, due to the loss of the influence of testosterone. However, there is no proof that this is true, as almost all cases of UC can be traced to improper nutrition.

Urinary calculi is a nutritional disease caused by improper diet, It is most common in small ruminants that are fed high concentrate-low roughage diets. These diets often contain too much phosphorus and/or an imbalance of phosphorus and calcium. Phosphorus is normally recycled through saliva and excreted via the feces. Low roughage diets decrease the formation of saliva which increases the amount of phosphorus excreted in the urine. Inadequate water intake is another contributing factor because it results in more concentrated urine and a greater likelihood of stone formation.

Signs of urinary calculi include anxiety, discomfort, and pain, as animals struggle to pass urine. Affected animals may stand hunched-up or kick at their bellies. Treatment depends upon the location of the stones and the extent of the blockage. If the animal is not completely blocked, drenching with ammonium chloride can help to acidify the urine and dissolve the stones. Tranquilizers and antispasmodics may also help to dislodge stones. Sometimes, the blockage is located at the tip of the penis and snipping off the urethral process may solve the problem. In more advanced cases and for blockages further up the urinary tract, surgery is usually necessary. All but simple blockages usually require veterinary intervention, and outcomes are not always positive.

Urinary calculi is almost always preventable with proper diet formation. The ratio of calcium to phosphorus in the whole diet should be at least 2:1. Care should be taken when adding phosphorus to the diet and feeding forages that have been fertilized with phosphorus. All ruminants should have a source of roughage (hay, pasture, or browse) in their diets. Anything that increases water consumption will help to prevent urinary calculi. Animals should always have a constant supply of fresh, clean water. Water troughs should be cleaned frequently and prevented from freezing. Shading water in the summer will increase consumption.

Salt intake will increase water intake and frequency of urination. It is better to “force-feed” salt (include it in the ration) than to offer it free choice. When it is fed free choice, it should be a loose form, not a block. Ammonium chloride is commonly added to small ruminant rations to help prevent urinary calculi.

Late castration might be considered if there’s a good chance the aforementioned feeding guidelines will not be followed. This is often the case with pet and show wethers. Late castration might make sense for wethers that will live out long lives, such as pack or pet wethers. Late castration is fine so long as it is done by a veterinarian.


Additional reading

Prevention of urolithiasis in livestock