Urinary calculi is a common metabolic disease among male sheep and goats. According to sheep and goat specialist Susan Schoenian, the disease occurs when calculi, which are small stones, become lodged in the urinary tract. The most common type of calculi according to Dr. Richard V. Machen, Associate Professor and Extension Livestock Specialist from Texas, is struvite. Struvite stones generally contain calcium, magnesium and ammonium phosphate. There are several causes and risk factors for developing urinary calculi.
Urinary calculi can be contributed to several different factors
The first factor is an insufficient calcium to phosphorus ratio. The calcium to phosphorus ratio for sheep and goats should be 2:1 according to Nolan Hartwig, Extension Veterinarian at Iowa State University. Diet can be a major contributing factor to the development of urinary calculi. High energy feeds, such as corn, are low in calcium and high in phosphorus. High roughage diets are high in calcium and low in phosphorus, which is more suitable for the prevention of urinary calculi. High grain, low roughage diets can cause an imbalance in the calcium to phosphorus ratio. The high grain diet decreases the formation of saliva causing an increase in the amount of phosphorous excreted in the urine. According to Schoenian, the primary cause of urinary calculi is feeding concentrated diets that are excessive in phosphorus and magnesium. Lack of water or water that is high in minerals is also a contributing factor.
The risk of developing urinary calculi depends on the type of urinary tract. Males have a much smaller urethra than females. The urethra is a tube that empties the urine from the bladder. The size and length of the urethra may make the stones more difficult to pass, as seen in the diagram below.
The Urinary Tract of a Male Goat
Males are more prone to urinary blockages than females because the urethra in males is much longer and smaller in diameter. The female urinary tract can pass small, solid particles a lot more efficiently than that of a male due to greater diameter and shorter urethral length. The urethra of early castrated males is even smaller than that of males that are castrated later in development. The reason for this is because the hormones that are necessary for the urethra and penis to reach full size are removed at a very early age. According to Schoenian, whether lambs and kids are at the greatest risk for developing urinary calculi because they are castrated at a very early age. Castrating after puberty can help prevent this from occurring.
Once the calculi or stones cause a blockage in the urinary tract the animal will begin showing symptoms of urinating difficulty. According to David C. Van Metre, DVM, at Colorado State University, the most common clinical signs of urinary calculi are loss of appetite and frequent attempts to urinate. There may be little or no urine flow during these attempts. Dribbling of urine and dried blood and or crystals around the opening of the urethra is also common. The animal will continue to strain and may become vocal while trying to urinate. Goats often become vocal because of the increasing pain during urination. As the bladder becomes increasingly full the animal may kick at its abdomen. The abdomen may appear distended or swollen. The bladder will rupture and the urine will be absorbed into the bloodstream. The urine that is absorbed into the bloodstream will have a toxic affect on the animal. If left untreated the animal will die.
Treatments for Urinary Calculi
Treatments are not always beneficial, however, one treatment that is available is an urethrostomy. Urethrostomy is required if the stones are lodged in the sigmoid flexure of the penis, which is located on the upper end of the urethra in the abdominal cavity. According to Jennifer Maas, DVM, the success rate of urethrostomy is about 50 percent and many complications usually occur after surgery. An urethrostomy may save an animals’ life, but the animal would no longer be able to be used as a breeder. If the stones are lodged toward the end of the penis, in the urethral process, the end of the penis can be surgically removed. Another treatment that is available is the use of ammonium chloride. According to Machen, oral dosing of ammonium chloride (0.20-0.33 g/kg body weight) can acidify the urine and dissolve the struvite crystals that are causing the blockage.
Ammonium chloride works best if the animal is not completely blocked. Ammonium chloride is also the most economically feasible treatment for urinary calculi. Urethrostomy is quite expensive and is plagued with complications. Therefore, prevention is the simplest way to deal with urinary calculi.
Prevention is Best
The prevention of urinary calculi is easier and more reliable than treatment. According to Schoenian, feeding rations containing calcium to phosphorus ratio of 2:1 can help prevent urinary calculi. Neither magnesium nor phosphorus should be added to feed rations. High grain, low roughage diets should be avoided along with unnecessary supplementation. Diets should contain adequate amounts of Vitamin A. According to Dr. Machen, adding 3 to 4 percent salt in feed rations will help increase water consumption. Water consumption is the most important management strategy one can employ in the prevention of urinary calculi. Free choice water needs to be clean and needs to be made available at all times. The addition of salt to the diet or as a mineral/salt supplement needs to be added to the management strategy. Never add salt to the water as it will decrease palatability. Ammonium chloride can be added to feed rations at a rate of 0.5 to 1.5 percent to help break down any crystal formation. Delaying castration of young lambs and kids as long as possible may also be beneficial in the prevention of urinary calculi.
Urinary calculi can be very harmful and is much easier to prevent than it is to treat. When caught at the first sign, the animal has a much more likely chance of recovery. Questions and concerns about urinary calculi should be dealt with by a veterinarian. When determining the correct feed rations and supplements for an individual heard, a nutritional specialist should be consulted.
This article was written in conjunction with Dr. Beth Walker's Feeds and Feeding course at Missouri State University.
