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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
A NOTE ON "GOITRE" IN LAMBS
D. J. WALKER. B.V.Sc., Inspector of Stock, Cooma.
During November, 1939, a mortality in lambs on the western side of the Narrabri Pastures Protection District was investigated; the sheep involved having been pastured on heavy black-plain country lightly timbered with Coolibah.
The owner of the holding, a careful grazier who kept accurate records, supplied the following information concerning the mating and the lambing:—
Mating commenced on 23rd May, 201 ewes were joined; 105 to one ram and 29 to another, both lots being hand-served, while 67 were joined to a third ram by paddock mating. Some losses occurred in the ewes from pregnancy toxaemia, but none from hypocalcaemia, over a period of about a fortnight approximately one month before lambing, when the feed which had been green was drying off very rapidly. Lambing commenced on 25th October, 79 and 22 Lambe were dropped by the hand-served ewes, and of these 61 and 16 respectively were living one month later; the majority of the deaths having occurred from "goitre." From the 67 paddock mated ewes there were about 50 lambs, of which 31 were living one month later.
The lambs generally were weedy, with knock-knees and uncertain gait. All were considered to be abnormal in some degree. Some showed little inclination to suck, while almost all had enlarged thyroid glands, which the owner stated had been sufficiently large in some cases to cause suffocation. The lambs with the more marked abnormalities were affected at birth, although odd lambs not noticeably abnormal when dropped developed "goitre" within a few days.
Two of the rams involved had been used at previous matings, and were used subsequently. The third ram still is in use (1944 mating), and although his use has resulted in a considerable amount of inbreeding no ill effects of a nature similar to that recorded have been observed since 1939.
12 gr. of sodium iodide daily for two days and then 12 gr. every second day for six days was administered prior to inspection, but without apparent effect. The Director of Veterinary Research, Glenfield, reported as follows on examination of thyroid glands forwarded from a lamb a few days old, and from a lamb born dead:— "In the case of the gland from the lamb which was a few days old it was seen to be greatly enlarged, anaemic and containing a cyst. Histologically it showed marked hyperplasia and generally showed poor production of colloid.
In the case of the glands from the lamb born dead there was evidence of autolysis, and very early hyperplastic changes. It would seem that these glands were affected by post-mortem changes and clear definition not so apparent as in the gland from the lamb which was a few days old.
Histological appearances of this tissue are of distinct interest and are similar to those encountered in sporadic goitre. This disease has been described in animals whose food intake includes an adequate supply of iodine, but on account of some factor so far undetermined the metabolism of the element is incomplete."
In the Stock Inspector's office at Narrabri there was no record of similar losses in the district. The owner of the holding, however, stated the some fifteen to twenty years earlier losses from an apparently identical condition had occurred in the same area.
Louis L. Madsen, of the Animal Nutrition Division, Bureau of Animal Imdustry, in the 1942 American Year Book of Agriculture suggests that diets high in calcium may be antagonistic to iodine absorption. This may be the underlying casual factor in this small outbreak, and although no definite conclusions are drawn the occurrence is considered to be of sufficient interest to record.