Urinary Calculi in Sheep

Urinary calculi or “water belly” is a very common metabolic problem of male sheep. The problem occurs when calculi (stones), usually comprised of phosphate salts, lodge in the urinary tract and prevent urination.

Normally, phosphorus is recycled through saliva and excreted via faeces in ruminants. High grain, low roughage diets decrease salivation and this leads to an increase in the amount of phosphorus excreted in the urine. Cereals are high in phosphorous and very low in calcium, which compounds the issue further.

The primary cause of urinary calculi is feeding concentrate diets which are excessive in phosphorus and magnesium and/or have an imbalance of calcium and phosphorus. Calcium, Phosphorous, Magnesium and Sodium levels in the feed are all factors but definitely not the only factors.

Lack of fresh clean water and water sources are also strong contributing factors as it results in more concentrated urine and less flushing of the system. Anything that reduces water intake (such as cold weather) and urine output can be trigger factors.

The pH of the urine and genetic susceptibility are also factors. Other possible factors include urinary tract infection, low roughage intake (affecting salivation), vitamin A deficiency, and excess intake of fluoride or sodium bicarbonate.

Gain Feeds includes products in its’ lamb and sheep finisher rations to improve the solubility of magnesium and phosphorous and reduce the risk of crystal formation in the urinary tract. This is achieved by making the urine more anionic

Who's at Risk?

While urinary calculi can occur in intact males, wethers are at greatest risk because castration of young males removes the hormonal influence (testosterone) necessary for the penis and urethra to reach full size.

In females, calculi are formed, but excreted due to anatomic differences in the male and female urinary tract.

What are the Symptoms?

Clinical signs vary. They usually start with restlessness and anxiety. Affected animals may experience abdominal pain, urine dribbling, distention and rupture of the urethra. They will usually experience a loss of appetite. They may have a humped-up appearance and oedema under their belly. They may kick at their belly and strain to urinate. Dribbled urine may be bloody.

If left untreated, affected animals will die when the bladder bursts and urine fills the peritoneal cavity and is absorbed into the bloodstream. Treatment is really the job of a trained veterinarian but farm management and feed composition offer the best opportunities for prevention.

Prevention is better than cure!

Correct diet formulation is the first step. Cereals are low in Calcium and high in Phosphorous (1:4 in ration), rendering them high risk feeds. Balancing the ration requires ideally a 3:1 Calcium: Phosphorous ratio or at least greater than 2:1.

The concentrate fed should be ideally above 1% Calcium, at or below 0.4% Phosphorous, at or below 0.3% Magnesium with salt and anionic salts added to promote water intake and decrease urine pH. Excess acidification of the urine will demineralise the skeleton over time (this would certainly be undesirable in pedigree stock kept for breeding or showing but less so in lambs destined for slaughter).

Achieving the right balance with all the various risk factors is very difficult to achieve on farm with limited raw materials, minerals and salts.

A well formulated compound feed is the ideal way to achieve and deliver the right balance/ratios of minerals and salts to encourage water intake, acidify urine and avoid the formation of phosphate calculi or stones.

First Published 21 October 2016