ARCHIVE FILE
This article was published in 1957
See the original document
INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Urinary Calculi of Wethers
Some Field Observations in the West Darling Area of N.S.W.
K. F. OPFERKUCH, B.V.Sc., Veterinary Inspector, Broken Hill
ECONOMIC IMPORTANCE
(a) Losses by Death
These are considerable: being 5-10% of the wether population of the West Darling area. As deaths occur in good seasons, when sheep usually are fat and carrying good fleeces, the economic loss is high.
(b) Losses Due to Selling Wethers Before Losses Commence
In good seasons the practice of selling wethers before they die of Urinary Calculi leads to serious depletion of the wool clip.
INCIDENCE
(a) Type of Sheep
All sheep run in this area are South Australian-type Merinos. Calculi occurs in wethers from six months old onwards, but losses in sheep under four-tooth usually are small in number. In old wethers the losses are more extensive. In one mob of 1200 aged wethers a loss of 400 occurred over a period of 12 months in 1956.
(b) Type of Country
The type of country on which losses occur varies from open limestone country carrying predominantly saltbush to sandy soils timbered with Gidgee and Mulga and growing speargrass and copperburr. Losses have not as yet been seen on the flooded plain of the Darling River, although they do occur on adjoining red, sandy soils. Heavier sandy loam country with Mitchell grass is country in which the trouble often occurs.
(c) Type of Feed Available at Times from Autumn to Summer
1. Saltbush, Bluebush and Copperburr.
2. Speargrass, Mitchell and Neverfail grasses.
3. Wild Spinach, Wild Hops, Daisies, herbage of various kinds.
Water: Ground tanks, bores. During outbreaks and in the period immediately preceding, sheep live on clay-pan water and on succulent green feed; and do not drink stored water.
SEASONAL CONDITION
Calculi usually occur in good seasons, when sheep have been on good green feed for a long period. During 1956 heavy rains fell during the late summer, autumn and winter; resulting in heavy growth of herbage in the autumn, winter and spring.
Losses were heaviest in the late spring some losses investigated being as follows:
| Property | No. Dead | Date |
|---|---|---|
| A | 6 | 26/5/56 |
| B | 80 | 16/2/56 |
| C | 20 | 4/7/56 |
| D | 400 | 3/9/56 |
| E | 80 | 17/9/56 |
| F | 120 | 19/9/56 |
| G | 80 | 31/9/56 |
All outbreaks investigated in 1956 occurred from May to the end of September; with heaviest losses in September. As soon as feed dried off in November the mortality stopped, except for occasional cases. Losses can be expected to cease as soon as sheep begin to water at tanks and bores; i.e., when lush green feed has dried off.
SYMPTOMS
Away from mob, stagger on driving, humped back, very unwilling to move; with sometimes vision impaired, swollen abdomen (if bladder ruptured). Dribble of urine, which is usually bloodstained, and discoloured belly wool. Show extreme pain on pressing abdomen; lie down and die. Symptoms may last days or sheep may die suddenly. Sometimes swelling of abdomen and legs due to urine in the subcutaneous tissue.
POST-MORTEM
Calculi varying in size up to that of a pea block the urethra; usually at the pelvic flexure, but may be formed elsewhere. The neck of the bladder may be blocked with many small Calculi like sand.
After blockage of urethra three different things may happen: (1) bladder ruptures; abdomen full of urine, up to 2 gallons in volume; sterile peritonitis with fibrinous deposits on all organs; the abdomen is grossly enlarged; (2) urethra ruptures; giving necrosis of wall of urethra and surrounding portion of penis, with sometimes secondary infection; subcutaneous tissue of abdomen, thighs and legs grossly distended with urine; kidney enlarged; urethras enlarged; (3) death due to uraemia occurs suddenly if the sick sheep is driven or caught and handled. Bladder is tightly distended and may measure eight inches in diameter, Blood vessels of wall grossly distended, with haemorrhages throughout; urethras enlarged to diameter of one inch; kidney twice normal size and sometimes hilus full of blood, and greatly distended; contents of bladder consists of bloodstained urine; the mucous membrane being necrosed and haemorrhagic.
Bladder and urethra may contain hundreds of calculi, ranging in size from 1cm in diameter down to a fine sand. These calculi are brownish in colour. Sometimes smooth, round and shining; but usually with a rough surface. All calculi analysed have consisted of Ca and Mg Carbonate.
CONTROL MEASURES
1. Sell off young wethers. This is the usual method and causes the greatest economic loss.
2. Starvation of sheep by confining in yards or small paddocks. This has been tried in two cases in this area. For instance:
Property 1: 400 out of 1200 had died. Sheep were shorn and kept in yards three days, then put in small paddocks with little feed for six weeks. Mortality stopped after one week of starvation.
Property 2: 2000 wethers; losses 60. Shorn and starved for four days. Losses ceased for 14 days following, but a few losses occurred after that period.
DISCUSSION
Urinary Calculi occur in wethers after very good seasons, usually winter and spring with abundant green herbage. The cause of the condition is obscure but may be due to high protein diet, kidney irritation due to high oxalate content of some plants (e.g. wildhops (rumex spp.), buckbush, wild spinach) or to faulty mineral metabolism. The condition never has been observed in rams running in this country, but may occur.
The most important of these observations is that calculi do not occur in wethers running on hot, dry country with limited water intake or mineralised bore water. Rather, calculi occur in wethers on a lush diet of herbage and grasses; following a very wet year. The aetiology of the condition appears to be associated with this diet, which contains high protein, and possibly is due to mineral imbalance. It is interesting to note that one outbreak of oxalate poisoning was investigrted during the same period. The only sheep affected were wethers, but calculi did not cause trouble on this property.
Control measures such as starving or putting on to poor feed may stop mortality, especially if feed dries off in late spring and the wethers then can be put back on to their original pastures. This method causes loss of condition and probably loss of fleece weight, and, as a result, is not popular except in cases where mortality is high.