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This article was published in 1971
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Congenital Aplasia Of Bile Ducts In Lambs
J. B. BARKER, B.V.Sc., Veterinary Inspector, Yass.
The properly concerned comprises 2000 acres situated on Burrinjuck Weir. At certain times of the year the water level of the weir drops considerably and this allows the property up to 300 acres extra grazing land from which the water has receded. 1700 XB ewes had access to this country from the middle of December, 1963 to the end of April, 1964, when the weir filled again. First lamb marking was carried out on 20th May, 1964 and the owners that 15% of 400 lambs showed marked jaundice, all of which subsequently died. The clinical appearance was extreme dejection, jaundice in whites of eyes and membranes, yellowish white diarrhoea. P.M. findings were jaundice throughout all tissues including bone and cartilage, liver enlarged and orange coloured, short lengths of small and large bowel showing haemorrhagic enteritis, contents of large bowel pale and fatty. A number of lambs were forwarded to D.V.R. and his findings in brief were "that this condition is due to congenital aplasia of the bile ducts resulting in a clinical picture of obstructive jaundice. The liver sections examined showed, (i) complete absence of normal bile ducts; and (ii) absence of normal bile ducts with early attempts to replace them together with marked portal tract fibrosis".
Blood samples taken from affected lambs, their mothers and the rams showed no evidence of any haemolytic factor operating. The possibility of a hereditary factor being involved was investigated with no positive results. Bacteriology yielded nothing of consequence.
Two further markings were carried out at monthly intervals. In the second marking 5% of lambs were affected and some of these recovered and in the final marking there were odd lambs affected only to a slight degree.
At the time of investigation, the pasture concerned was under water so no suitable plant samples were available. Usually this type of country grows water couch, clovers, heliotrope and large quantities of various weeds including "Trailing Knotweed" und "Sneezeweed".
As the ewes were not affected at any time it appears that during the gestation period they were transmitting some toxin to the foetus.
The incidence appeared to be related to the time of the gestation period spent on the marine type of pasture. The ewes lambing in April had been grazing on it for four months and the incidence was 15% jaundiced lambs. Ewes lambing a month later produced only 5% and in the final marking the percentage was negligible.
All this country was available to stock during the dry years of 1965-6-7-8, but there was no recurrence of this condition, but in 1968, thirteen hundred ewes running on this pasture were drenched with carbon tetrachloride and incurred a 10% mortality in the following seven days.