Obstructive urolithiasis, urinary calculi, stones

Obstructive urolithiasis, urinary calculi, or stones is a disease where crystals are formed in the bladder, usually the result of deviation from the desired dietary ratio of calcium (Ca) to phosphorus (P) of two to two and one-half parts Ca per part P (2:1 to 2.5:1). The crystals can lodge in the urethra of male goats preventing them from urinating. Female goats are largely unaffected and the disease is most commonly seen in male goats consuming large amounts of concentrates, such as pet goats. It is virtually non-existent in animals that receive little to no grain with the exception of animals grazing western pastures with high silica content.

Types of urinary calculi

Stones regularly associated with calculi formation in goats include silicate, calcium (calcium carbonate, calcium oxalate), and phosphate (magnesium ammonium phosphate called struvite). While calculi can form in any geographical region, silicate stones are generally limited to goats grazing forages grown on western pastures that have excess soil silica content.

Calcium carbonate stones result from feeding rations very high in calcium, typically high legume diets (clovers and alfalfa) such as seen in the major alfalfa producing areas of the U.S. Legumes contain 1 to 2% calcium and have very high ratios of calcium to phosphorus (Ca:P of 6:1 to 10:1). Calcium oxalate stones form as a result of diets high in calcium and in oxalates. Certain plants are oxalate accumulators (rape/kale family, rhubarb, sugar beet tops, pigweed).

Phosphate or struvite stones occur when feeding rations having a disproportionate ratio of Ca to P (< 2:1) or high levels of magnesium and phosphorous. In general, grasses are low in magnesium, Ca, and P but are balanced in terms of Ca:P ratios (1.5:1 to 2:1). Thus, grazing goats rarely experience urinary stone problems. Rather, affected goats typically are fed high levels of grain and/or pelleted feeds. Grains are high in P and low in Ca and have Ca:P ratios of 1:4 to 1:6. Most P in grains is bound in phytates and cannot be absorbed by non-ruminants (horses, pigs, etc.). In ruminant animals, bacteria in the rumen produce enzymes (phytase) that break down phytates freeing the P for absorption. This is the reason why dietary P requirements for ruminants are lower than those for monogastric animals and why diets for monogastric animals generally have high P concentrations. Thus, feeding swine or horse rations to ruminants is a bad idea from the standpoint of Ca and P because of the high amount of P in the feed. Every feedstore has an “All Stock Pellet” which they claim can be fed to any animal. These mixes are not appropriate for prolonged feeding to male goats Contributing factors

There are several factors that can contribute or predispose an animal to suffering from urinary calculi. These include early castration, the pH of the urine, and inadequate salt intake. Early castration of ruminants results in decreased diameter of the urethra, the passageway for urine, increasing the chance of blockage. If castrated male goats will be kept into adulthood, castration should be delayed until puberty (3 to 4 months of age).

The normal alkalinity found in ruminant urine favors the formation of urinary stones. Reducing the pH to acidify the urine reduces the likelihood of crystal formation. To acidify urine, goats receiving high grain or concentrate diets can be fed ammonium chloride up to 2% of the total ration (200 to 300 mg/kg diet/day) or ammonium sulfate at 0.6 to 0.7% of the ration. Ammonium chloride is unpalatable and higher levels will reduce intake. Alternately, feed ¼ lb/head/day of Bio-Chlor, a highly palatable protein supplement with high levels of chlorine and sulfate that is used in the dairy cow industry. Urine should be acidic within one week.

Ensure that animals have access to salt and fresh, clean water. The chlorine in salt helps prevent crystal formation. Salt also acts to increase water consumption and subsequent urination that keeps the bladder flushed. Goats are finicky drinkers and will not drink dirty, tepid, algae-infested water, etc. Hard water can be a source of calcium and magnesium. Keep fresh, clean, chlorinated water available at all times.

Signs and symptoms

The main sign is a male goat persistently straining to urinate but passing little to no urine. Urine may be blood-tinged. Drops of urine and blood or urine crystals may be seen on the hair of the sheath. Affected animals will be restless, switch their tails, and kick at their bellies. As the blockage progresses, some goats will vocalize in pain. The bladder will be enlarged with possible swelling around the sheath. Some goats will eventually pass the stone but are likely to have continual problems.

Severe blockage can lead to the rupture of the urethra or bladder. Initially, this will alleviate the discomfort felt by the animal. However, due to urine inside the body, the animal will quickly go off feed, become weak, depressed, and eventually die.

Treatment, prevention, and control

There are varying levels of treatment that can be attempted. Acidifying the urine, increasing salt content of the diet, and Vitamin C may help dissolve the calculi. If the calculi or stones are lodged in the urethral process (the whip-like structure at the end of the penis), the process can be removed. Gritty, sandy material present in the urethral process can sometimes be successfully milked out without removing the process itself.

If the stones are lodged in the urethra, tranquilizers may help relax the muscles of the urethra and facilitate natural expulsion of the stone by the pressure of attempted urination. A catheter could be passed into the urethra to permit infusion of sterile saline in an attempt to enlarge the urethra and dislodge the offending stone. For severe cases in valuable animals, surgical methods may need to be used. For some animals, salvage slaughter may be chosen but must be done prior to bladder rupture.

Dietary management is the key to controlling and preventing urinary stones. Maintain a Ca:P ratio of 2:1 to 2.5:1 in the diet. Do not feed excess grain supplement to goats. If a high grain diet is fed, include products such as ammonium chloride, ammonium sulfate, or Bio-Chlor to acidify urine and(or) increase the salt content. Ensure an adequate supply of clean, fresh water. Delay castration until puberty if planning on keeping the animal as an adult or do not keep early castrated males older than one year. Provide a free-choice loose mineral mix with 2:1 Ca:P ratio.

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