Urolithiasis in Pygmy Goats
Nancy Walters, DVM
(reprinted by permission from Pygmy Goat WORLD magazine, Nov. 1995)
Many goat owners live in fear that their wethered goats or bucks will, sometime in their lives, develop obstruction because of urinary calculi. Many of us feel helpless because of the potential problem.
You can help avoid urinary calculi in by applying some basic principles of husbandry and becoming aware of some important behaviors in goats that predispose them to stones. Most importantly, educating the prospective new owner about these principles of care can be their first line of defense in preventing problems.
Although we don't have all the answers, I hope the following articles will provide some new insights and understandings as to why the problem occurs, what options and approaches are available when a goat becomes obstructed and what measures we might employ to help avoid the problem.
Two fundamental principles are involved: how urinary calculi form, and the life-threatening condition that occurs when stones lodge in and obstruct the urinary system.
The urethra is a tube that empties urine from the bladder. Illustration 1 shows why male goats are more prone to obstruction; the male's urethra is much longer and narrower than the doe's. Even though does may certainly develop stones, we don't tend to see this as a clinical problem as they generally pass through.
Stones are mainly formed in the bladder. We usually don't have a problem until a stone becomes lodged in the urethra. This causes acute discomfort and inability to urinate. A common misunderstanding is that if the troublesome stone is removed, the goat will be free of any further problems. Unfortunately, the odds are that many more stones are present (usually at the neck of the bladder) or, quite commonly, lodged in urethra just as it narrows ver the pelvic arch below the rectum. I've removed as many as 32 stones from this area.
The S-shaped sigmoid flexure just behind the testicles is another area which is quite prone to calculi obstruction. An even more common location is at the end of the penis where the small-diameter urethral process extends beyond the penis. This extension is often poorly developed in young castrated goats and may even be fused to the end of the penis making it very diffcult for the veterinarian to recognize the urethral opening or to pass a catheter.
Another anatomical "quirk" in the male is the urethral recess found in all male ruminants (sheep, goats, cattle). As the urethra exits the pelvis just below the anus, there is a small blind pocket arising from the urethra. This can make it virtually impossible for the veterinarian to pass a urinary catheter into the bladder in the attempt to flush lodged stones or establish urine flow. Inevitably, the catheter gets caught in this blind pocket.
Factors Influencing Stone Formation
The formation of urinary calculi results from the interaction of numerous physiological, nutritional, and management related factors. The tendency of the stone to become lodged, as we have seen, is determined by the anatomy of the urinary tract and age at castration.
Urine is a highly saturated solution of dissolved minerals. Normally these solutes stay in solution and won't precipitate out to form calculi. Factors which influence precipitation (separation of a solid substance from the solution) of minerals are:
Decreased water intake and consequently very concentrated urine
Increased water loss due to dehydration, heat
Insufficient water provided or lack of potable (fit to drink) water
Urine stasis (stagnation)
Increase in urine PH (Alkaline urines allow cer tain solutes to precipitate)
Increase mineral composition in the diet or im balances
The precipitates can be in the form of crystals often seen in a urinalysis or sandy, gritty material. Because the precipitates occur over a long period of time, the tendency is in the formation of stone from an initial small nidus, such as from free cells along the bladder wall (seen with vitamin A deficiency), or urinary tract infections. Once a stone begins to grow, often other components in the urine, such as an increase of mucoproteins, can act as a matrix and stimulate further concretion. Grain and pelleted feed promote increase in mucoproteins which are excreted in the urine. Figure 18* shows how this works.
Calculus formation frequently reflects diet and this is a very important factor individual owners should look at when attempting to prevent problems. When you have a goat with a calculi problem, getting a sample stone and having it analyzed for its mineral composition can provide you with insight as to the possible source of the dietary imbalance. (Quantitative analysis is preferable).
Stones are made up of many different kinds of minerals. The most commons ones are:
Silicates from grass and cereal hays, particularly in arid regions
Phosphate salts, struvites (magnesium, ammonium, phosphate), and apatite (calcium phosphate) usually from excess grain diets
Calcium ammonium magnesium carbonate, found commonly in pastures where plants concentrate calcium, oxalates and clover rich pastures
From my own subjective point of view, I find mostly calcium carbonate stones in Pygmy goats in my area of Northern California. It seems to be associated with diets restricted to only alfalfa or pelleted alfalfa.
Measures Important in Avoiding the Problem
No rigid dietary formula can be followed that can prevent stone formation. Individual situations must be evaluated from the standpoint of diet and management. I think its important to emphasize balance and variety in the diet. Goats are browsers. They don't eat the same food every day, all their lives.
We know that oat hay, grasses, and grains are very rich in phosphorous and that alfalfa is very rich in calcium. Fed as the sole ration, either one of these can predispose the goat to calculi. We like to see a calcium to phosphorous ratio of 2:1. Rations high in grass hay and concentrates (grains) will most likely produce excess phosphorous and, consequently, phosphate stones. When possible, a ration of high quality, free choice, mixed alfalfa/grass/oat hay with salt and trace minerals is best. Freedom to browse is an added plus.
Concentrates have their place in the overall balance and should not be fed at more than 1% of the body weight, depending on energy needs - breeding, pregnancy and lactation - and size of the animal. As a general rule, I give adult Pygmy goats no more than 1/2-3/4 cup grain/day. If they eat more alfalfa and not so much of the oat hay I may give them more.
I don't recommend pelleted feeds for several reasons. You are often unaware of weeds and other constituents in the pellet. A high roughage diet is crucial in maintaining a healthy, functional rumen (digestive system) In addition, low roughage diets (such as pelleted feeds) foster increased mucoproteins in the urine which act as a cementing factor in stone formation.
Have fresh water available at all times. Goats are very finicky about their water. Water intake is essential for a good, dilute urine flow and to avoid solute precipitation. In the winter or rainy months make water easily accessible. They won't got out in the rain to drink! Offer warm water at these times as they don't like cold water. Urinary obstruction is often seen in late fall and winter when goats are stressed and stay under shelter. Water consumption decreases because of stale water or a cold, inaccessible source. If you have highly mineralized well water, change their water source or filter it if possible . If you have problems getting them to drink or a history of stones in your herd, increase the concentration of salt in their diet up to 4% of the ration.
If calculus analysis consists of phosphate minerals, prophylactic use of urinary acidifiers can be helpful. Normal urine pH in herbivores is alkaline (greater than 7) and in this environment phosphate calculi are more likely to precipitate. Administration of ammonium chloride salt at a level of 2% in the concentrated ration is recommended. For example, if you are feeding 1/2 cup of grain/day - that equals 120 ml and 2% of that equals 2.4 mls, or 1/2 teaspoon of ammonium chloride a day. I usually have owners divide that into 1/4 teaspoon salt in 1/4 cup grain morning and night. By testing their urine with litmus paper (available in drug stores) owners can assess urine acidity. One must be very careful in the amount of ammonium chloride given. There is a fine line between therapeutic benefits and toxicity.
Deferring castration until 3 to 5 months of age may reduce the incidence of obstructive calculi. This allows the influence of testosterone on the development of the urethral lumen size. It also helps the urethral process separate completely from the its attachment to the end of the penis. This involves more management by the owner because the young males are so precocious and capable of impregnating as early as 3 months. In addition, because the older male requires sedation and more involved castration, the expenses are greater.
Approach to the Clinical Problem of Urethral Stones
When you are faced with a goat who is potentially obstructed, what do you look for? How much time do you have before it becomes a life threatening situation? What needs to be done?
In the first phase of obstruction, a male goat will show restlessness and anxiety. Often he will stand with his back legs stretched back and all his weight leaning forward on the front legs. You may see a pumping action and twitching of the tail. He do this frequency and sometimes vocalize. You might notice drops of bloody urine from the penis, no urine stream at all or, with a partial obstruction, an intermittent stream and discomfort. I'm often amazed by the tolerance these goats have to the obstruction. As the condition progresses, some goats will just lie down and stop eating and drinking. This is the phase that commonly alerts owners that something is wrong. If not treated, the goats will become progressively weaker and depressed to a moribund (about to die) state due to the build-up of toxins in the blood. There is also potential for bladder rupture, but usually the goat has been sick and depressed for several days before this occurs.
Diagnostic and Medical Management
A definitive diagnosis of urinary calculi must be made by your veterinarian. Your description of your goats clinical behavior at home is very important information. Examination and history are critical because there can be other medical reasons why a goat is down and not eating. Indigestion, gastrointestinal obstruction, infection, and liver and kidney problems can often present the same symptoms.
Usually on presentation to the veterinarian, the goat is standing and alert and has a very painful, full, hard bladder that can be palpated high into the caudal abdomen in front of the pelvis. Often the goat will resist dramatically and cry out. Palpation of the urethra just below the anus will demonstrate a firm pulsating urethra.
Checking the BUN (blood urea nitrogen) is an excellent way to assess the severity of the condition. This measures the level of toxins building up in the body. These toxins are normally excreted in the urine. As more toxins build up in the blood, the more depressed the animal becomes.
During this preliminary phase, if the goat is looking fairly comfortable, your veterinarian may choose to sedate him and give an anti-inflammatory agent such as Banamine™ to counteract spasm of the urethra. Hopefully, he will pass the stone that is causing the immediate obstruction and pain. This is also a good time to examine the urethral process for a stone. The urethral process can be easily excised in an attempt to restore urine flow. At the University of California, Davis, 40% of the cases in one study had obstruction at the urethral process and amputation of the process may temporarily restore urine flow. This surgery alone will not affect breeding ability in the buck. It is very important to remember, however, multiple calculi are usually present. A thorough assessment of the state of the animal, palpation of the remainder of the urethra and attempts to pass a catheter to find other stones are critical diagnostic methods in understanding the scope of the problem. X-rays are most useful for detecting calculi along the urethra, and they are most commonly seen at the neck of the bladder and the ischial arch. Occasionally the task may involve only flushing sandy crystalline material from the distal urethra.
Depending on the goat's condition, the veterinarian may want to observe him in the hospital for 24 hours. More invasive procedures will need to be discussed and decided upon at that time.
Once the extent of the stones has been determined, one or more surgical procedures may be required. Further treatment will depend on the stage of disease in the animal, the intended long term use of the animal and financial constraints.
Stones in the bladder definitely indicate a need for abdominal surgery, opening into the bladder (cystotomy) for stone removal as well as possibly making an incision into the urethra (urethrotomy) for complete removal of all stones. A urethrotomy alone has resulted in a stone recurrence rate of 45% within 8 months of surgery at the University of Davis. The importance of the removal and identification of all stones along the urethral tract and in the bladder cannot be overemphasized for the best long-term results.
Even with the best surgical outcome there can be many frustrations and potential postoperative complications owners may be forced to address. Strictures (closing) at the urethral incision may occur and a permanent opening site may be required (urethrostomy). This will cause loss of breeding capability and potential management problems of urine scald on the hind legs and perineum. There can be a fair amount of pain and spasm involved which leads to a failure of eating and drinking and a need for extended hospitalization and treatment. There is potential for infection and hemorrhage, and always a risk of new stones and reobstruction. In some cases, I have had to operate and establish patency three times to create a permanent opening into the urethra below the anus. In others I have only removee stones and the animal healed, urinating normally from the penis. Some have lived 8 or more years with a permanent urethrostomy site, and some have blocked again a year or two after surgery.
As you can see, there is much to consider. There needs to be a tremendous amount of communication, trust and understanding of the problem each step of the way in order for you to make the appropriate decisions. Cost is certainly a big factor. You may spend a great deal of money and still lose your favorite pet.
Urinary calculi formation has a complex etiology. Because we cannot control all the physiological factors which can cause the problem, we cannot follow a set protocol to prevent it. Understanding that there are certain management, nutritional and anatomical considerations which predispose the male goat to the condition is helpful. Certain mineral imbalances, dietary extremes, water consumption and behavior must be carefully evaluated.
If the problem does arise in your herd, I feel it is critical to have individual stones analyzed for their mineral content in order to help define the problem. Feeling comfortable and confident in your veterinarian is certainly a benefit when it comes to making some very important decisions. Each situation is unique, and the extent of the condition must be assessed before any prognosis can be given. Remember, frequently there are multiple stones, not just one isolated stone.
1) Blood, Radostitis, Henderson, Veterinary Medicine (6th ed)
2) Garrett PD. Urethra recess in male goats, sheep, cattle and swine, Journal of Am. Vet. Med. Assoc, 191:689-691. 1987
3) Pasquini, Atlas of Ruminant Anatomy 180-186, 1982
4) Smith MC, Sherman DM, Goat Medicine 388-402, 1994
5) VanMetre, DC, Smith BP. Clinical Management of Urolithiasis in Small Ruminants, UCD
Castration & Urinary Calculi - Cornell University
Don't Let Urinary Stones Get Your Goat
Urolithiasis in Small Ruminants - The Ohio State University
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