URINARY CALCULI - A METABOLIC DISEASE

Urinary calculi or bladder stones as they are sometimes called, can affect male goats from four months upwards. It is a metabolic disease of both wethers and entire males.

They can be found anywhere in the urinary tract, in the kidney, the ureters, the bladder or the urethra. However, the condition is usually caused by the deposit primarily of phosphate crystals which collect in the bladder and pass into the narrow penis, the urethra, causing obstruction and blockage to urine flow. The urethra is narrower in castrated animals as castration arrests penile development .The most common problem for wethers is urinary calculi. Although formation is probably equal in both sexes, the female's urethra is short and large and as such is not as susceptible to obstruction.

Symptoms
Signs associated with bladder stones can be varied, depending on the site and size of the obstruction. Calculi found either in the kidneys or ureters produce no symptoms providing that the body is able to adjust to a certain lack of function of these organs.

Stones lodging in the urethra can cause partial or complete blockage. With partial obstruction, there could be a dripping of bloody urine, discomfort, some straining to urinate and lack of appetite. The bedding could be unusually dry with little evidence of recent urination. Initial signs could be mild. Complete obstruction could result in a distended bladder with signs of abdominal pain or colic. The goat appears to be restless, grinding its teeth and kicking at the abdomen. The belly hairs at the end of the penis, normally wet, may appear dry with the animal's back legs extended backwards.

If the blockage is not alleviated, perforation of the bladder or urethra can ensue, with possible fatal consequences. Any suspect symptoms should be acted upon immediately and veterinary assistance sought. Recognition of the condition and prompt action is paramount. The longer the goat is unable to pass urine, the sicker it becomes. 'Urinary obstruction is a medical emergency' (Orlando 2000). Treatment depends upon the site and size of the obstruction.

Potential Causes
Faulty Diet. Certain diets promote stone formation. Concentrates high in phosphates increase the concentration of the phosphate ione in the urine. Phosphate calculi form more readily in alkaline urine. Too high a ration of concentrates can also produce a cementing factor in the urine which encourages stone formation.

Low fibre diet. Goats on high grain/low fibre diets secrete much lower amounts of saliva than those on high roughage diets which in turn decreases the amount of phosphorous excreted in the faeces.

Concentration of Urine. Precipitation is more likely to occur if urine is not diluted, which makes a good intake of water essential. Feeding concentrates instead of roughage reduces urine volume.

Excess of Ingested Minerals. Excessive mineral in-take increases the urine concentration of these minerals.

pH of the Urine. Phosphate crystals are more likely to form in alkaline urine and silicates in acid urine. The pH of the urine varies according to diet and the length of time since eating, although the urine of goats tends to be generally alkaline rather than acid. Bacteria present in the urine can produce ammonia which makes it much more alkaline. Infections therefore create an alkaline environment and should be dealt with immediately.

Nidus Formation. Calculi form around small amounts of cellular called a nidus and kidney or bladder infections tend to increase the amount of debris that stones form around.

Urethral Size. Castration arrests penile development and therefore the urethra remains narrow. Younger castrated animals are at greatest risk but it should be remembered that the smaller diameter of the urethra of a wether makes the goat more susceptible to blockage but not to stone formation itself. It is doubtful if delayed castration would decrease the incidence of urolithiasis in wethers, although some people recommend that castration should be later rather than sooner to allow the urethra to mature.

Individual Genetic Make-up. Some animals are more prone to stone formation than others and will produce stones whilst others in identical circumstances do not.

Prevention of Calculi Formation.
Prevention is of prime concern both before and after blockage. Urinary obstruction can have fatal consequences and owners can do much to reduce the incidence and to prevent reocurrence.

Identification of Stone Composition. Identification of the stone composition is the first step so that the reduction of those specific substances contained therein can be attempted. Also, incorrect management practices can perhaps be remedied.

Increasing Urine Volume. Make sure that a clean and adequate water supply is always available, especially in the winter. Change twice a day and offer warm water in the winter.

Feeding Alfalfa hay and Lucerne. Alfalfa appears to increase the flow of urine possibly because of its higher protein concentration. It is also high in calcium which could tie up the phosphorus ion, a possible ingredient of a calculi.
Lucerne is also high in calcium. Dried grass products are better fed than a diet high in concentrates.

Considering the Ca:P ratio. As phosphorous is contained in the majority of calculi a calcium/phosphorus
Ratio of 2-2.5:1 will help to keep the phosphorus in solution. Adding ground limestone to the concentrate ration or feeding alfalfa will help achieve this. (Matthews 1999,Orlando 1991).

Adding Sodium Chloride to the Diet. Adding sodium chloride to the diet concentrates - 4% increase will be required to alter water intake - thus discouraging the formation of crystals. (Matthews 1999).

Adding Ammonium Chloride to the Diet. Matthews (1999) suggests that in problem herds ammonium chloride can be given in either of two methods:
(a) 10g dissolved in 40ml water by mouth daily
(b) 40mg/kg daily in feed. It is not very palatable and would need to be disguised in molassed food .
Another suggestion by a goatkeeper in a letter to Dr. Orlando (Memo vol XXll No.3 '97) is to add a teaspoonful per day to the male's concentrates. Dr. Orlando herself suggested in the same edition, 5-10 grams per head per day or 2%-5% of the concentrate ration. Ammonium chloride and citric acid (one chewable tablet daily is a convenient way of administering Vitamin C) both cause the urine to be more acidic and phosphate calculi are therefore less likely to form in such an environment.

Deferred Castration. As has already been stated, castration arrests penile development leaving the urethra narrower but opinions appear to vary on the advantages of deferred castration. Orlando ('91) states that there is no scientific evidence to support deferment But Maas,DVM (B.O.M.'82-'87) suggests; "Castration at an early age (1-4 weeks), slows down growth and development, resulting in a juvenile penis and urethra (narrower lumen and persistent adhesions of the penis to the prepuce)"

Checking Content of Trace Mineral Salt. The amount of phosphorus and magnesium in any mineral/vitamin used in the diet should be checked as there is often a wide variation. Copper levels, too, need checking.

There are many variables involved in the formation of urinary calculi in goats and it is therefore difficult to be specific when it comes to outlining a prevention and treatment programme which applies to all breeders and all goats. Many will never have a problem whilst others could experience many cases even when following best management practices. It is essential to work with your vet. who can take individual circumstances into consideration .If there is perceived to be a problem, NEVER hesitate to seek veterinary assistance.

-- Pat Mercer

N.B. In researching the topic of urinary calculi for the benefit of our readership, I have used only what I considered to be reputable sources. However, not being a vet., I am not in the position to validate any advice or information given. Anyone contemplating a change of management practice or feeding regime as a consequence of reading this article would be strongly advised to confer with his/her vet. beforehand. I cannot be held responsible for any consequent mishaps.
P.M.

Bibliography

J.G.Matthews Diseases Of The Goat Blackwell Science 1999.

P.Dunn The Goatkeeper's Veterinary Book Farming Press 1994

L.Hetherington All About Goats Farming Press 1992 & J.G.Matthews

J.Maas "Urinary Calculi" Pygmy Goats: Best of Memo 1982-1987

Dr.K.H.Orlando "Urinary Stones" Pygmy Goat Memo VOL.XXV No.6 2000

Dr.K.Orlando "Questions For Kay" Pygmy Goat Memo VOL XXII No3 1997