Following the winter rains of June, July and August, 1938, which fell in the Tamworth district, when lush grazing conditions resulted over a large area of that district, there appeared a considerable number of cases of sickness amongst heavy-in-lamb and wet ewes.
The complaint appeared on many holdings where grazing conditions can only be described as luscious. It appeared in ewes grazing on young wheat and oat crops, as well as when grazing on a mixture of herbage common to the rich country of this district, comprising amongst others, Lamium amplexicaule, clovers, trefoils, chenopodium atriplicium. etc., and in many instances the diet was confined wholly to the latter plant. Consequently, many owners were satisfied that the cause of the trouble was "Lamb Tongue Poisoning," when the losses were actually due to hypocalcaemia.
All cases recorded occurred in breeding ewes within from six weeks to lambing and in wet ewes in full milk with lambs to six weeks old. Out of the cases investigated, 75% were apparently due to or inspired by driving or some movement, even a short distance. For instance, in a mob of 600 forward-in-lamb ewes that were grazing on a young wheat crop for some days, portion of the mob were sold and placed on the road. By the end of the second day on the road, 40 cases appeared, with an 80% mortality of the number affected: treatment was not attempted. In another case of 740 cross-bred ewes with lambs up to six weeks old grazing on river frontage black herbage country, were removed from that paddock, put on the road to travel to the home station for shearing. Three miles were travelled that day, and next morning 150 ewes were affected. Eleven died before treatment. The remainder recovered after treatment was applied.
Many similar cases such as these were investigated, but space will not permit of a full description of all. Affected sheep presented a few more or less characteristic symptoms which may develop in a few hours and death may occur relatively quickly (4 to 6 hours), although it was not uncommon for animals to linger for two or even three days. and about 2% of the number affected would recover after perhaps the third day following the attack; others were seen to spontaneously recover much quicker.
Symptoms exhibited were shivering, a stilted poppy gait, involving the hind or all four legs, back arched, disinclination to move, and little or no faecal evacuations; lying down on sternum, head outstretched along the ground with chin on ground, and in many instances the hind legs straddled out behind the victim. If the animal were lifted and forced to move, it would shiver and tremble whilst in motion; walk a few yards and collapse in its tracks and lie in this position until recovery or death. Usually there was a discharge of fluid ingesta and mucous from the nostrils, most noticeable when death was near. Pneumonia was frequently a secondary complication, particularly if affected animals were exposed to inclement weather.
Post-mortem findings are more or less characteristic—in most instances the omasun was contracted into a firm lump about half its usual size. The rumen and reticulum were found filled to capacity with unmasticated sour-smelling ingesta; when grazing on young wheat crops, leaves of this cereal up to three inches in length being retrieved. On other feed, the ingesta would be broken up and frothy. The contents of the abomasum are liquid and no apparent lesions involving the organ. The caecum and large intestine distended to full capacity with gas, and in some instances as large as a football; it may also contain a little, almost solid ingesta, similar distension of the colon was frequently noticed, the ingesta in the solid lump interspersed with quantities of clear jelly-like exudate. The mesenteric lymph glands are frequently oedematous and the mesenteric vessels engorged. The liver and kidneys are congested. The gall and urinary bladder distended, some petechiae are frequently present about the heart.
The symptoms and history of affected sheep so closely resemble Grass Tetany of cattle that experimental treatment was attempted. Such treatment consisted of intravenous injection of equal quantities of a 15% aqueous suspension of calcium gluconate and 5% soution of Mag. sulph., and the results were little less than astounding. The dose varied from 20 to 40 c.cs. in advanced and severe cases. It was later found that the calcium gluconate would effect a cure without the addition of Mag. sulph., but the latter would cause a collapse if given alone.
Less seriously affected ewes would respond to treatment and be on their feet in a few minutes. Those more seriously involved, at the point of death, comatose and in extremis, would generally respond more slowly, but would usually be on their feet within an hour. As soon as the animal regained its feet, it would urinate and defecate although still affected with the shivers and trembles that would gradually disappear.
Up to 30% of ewes have been involved, 2% may recover spontaneously without treatment. The balance will die unless treated. In the case of wet ewes, inflation of the udder was carried out which, no doubt, assisted in the recovery of these cases.
Chemical analyses were undertaken at the Veterinary Research Station, Glenfield, in respect to certain cases, when fairly marked hypocalcaemia and slight hypermagnesaemia were found. A slight weak bowel toxin was also found.
It was found that the making available to the sheep a di-calcic phosphate lick or roughage of any kind (sic).
To prepare the calcium gluconate solution, take 5 ozs boric acid, 20 ozs. calcium gluconate, 100 ozs. water. Boil until clear.