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This article was published in 1989
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Neonatal Jaundice in Lambs and Calves
D.B. UNGER, Veterinary Inspector, YASS
In June 1988 I received a call to investigate white scours affecting three to four week old merino X poll dorset lambs on 'ME', a property adjoining Burrinjuck dam.
The observed problem of white scours, weight loss and failure to thrive, and death in lambs whose mothers had plenty of milk was noted over the previous two weeks. Approximately 30 lambs had died and 15 were sick at this time.
All affected lambs were bright and active but weaker than normal lambs, had greasy yellow/grey soiling down the breach and hocks to the hooves, their mucus membranes were jaundiced, they looked lighter than unaffected peers, and were 'hollow' or 'tucked-up' in the abdomen. Faeces were thick, white and voluminous.
Faeces and lithium heparin blood was taken from five cases and two animals were autopsied.
In addition to the white scours and greasy dags, both lambs were jaundiced. One, a female, had an enlarged head due to subcutaneous yellow fluid which also extended down the neck to include the brisket. All subcutaneous areas and tissues were jaundiced. The liver was enlarged, yellow and apparently fibrosed as it was hard to cut; the kidneys were an olive green colour; the gastrointestinal tract was full of greasy, white, foamy contents with a little blood on the mucosal surface. The overall appearance of the gut being similar to chicken gut. Other organs appeared grossly normal.
A male lamb was also autopsied. It had no subcutaneous oedema, but like the female all tissues were jaundiced. The liver was smaller, not yellow or fibrosed, and again the intestinal tract was full of white contents.
A sample of urine from this animal tested +++ for blood and reacted strongly for bilirubin.
My differential diagnosis at this stage included colibacillosis, mycotoxicosis and a congenital liver dysfunction.
A further six lambs were submitted live to Glenfield. Findings were similar to those described above. It was also noted that most livers showed shrunken, empty gall bladders with thickened, fibrotic walls. The cystic ducts in all cases were fibrotic and in some lambs were non-patent.
HISTOPATHOLOGY:
There was moderate variation in the findings from the various lambs, but generally they may be summarised as a deficiency in the biliary tree with diffuse absence of intrahepatic bile ducts, distension of biliary canaliculi with bile forming 'lakes' and fibroplasia.
When speaking to John Plant, he drew my attention to an almost identical account recorded by Hungerford from 24 years previously which I quote under the heading:
'JAUNDICE OF NEW-BORN LAMBS'
In 1964 at Yass on the Murrumbidgee River, a condition of congenital aplasia of the bile ducts, producing a clinical picture of obstructive jaundice, was reported. The condition apparently was associated with grazing herbage on land from which the river had receded during the dry autumn. This was noted in crossbred ewes mated to Dorset Horn rams. Sixteen lambs died and 40 more were affected from breeding ewes. (Hungerford Diseases of Livestock, 8th Ed., p. 162)
The property referred to in 1964, 'Bloomfield', adjoins the one affected in 1988.
In this case, genetic disease appeared to be eliminated by the fact that the owner had never seen the problem before, even though the sires and dams were the same as used in previous years.
A common factor in both 1964 and 1988 was the grazing by pregnant ewes on silt flats which are exposed when the water level in Burrinjuck Dam falls below capacity.
The 'ME' property is undulating, with 1000 hectares of improved clover/grass pastures. There are approximately 200 hectares of flats on the foreshores of the Burrinjuck Dam which are normally under water. At certain times of the year, the flats are exposed and there is a prolific growth of weeds on the exposed areas. The weeds that predominated in 1988 were Centipeda cunninghamii, and Dysphania glomulifera spp glomulifera.
In 1988, sheep management was changed such that the flats were fenced off and some sheep were restricted to the area during pregnancy and lambing. In previous years, the sheep always had access to adjacent country that was distant from the flats.
The grazing and lambing history of the two affected flocks from which a total of approximately 300 lambs died in 1988 was:
(i) 70 Border Leicester-Merino cross ewes joined to Dorset rams from 15 November 1987, for an extended period. These sheep were grazing on the flats for the joining period and commenced lambing on the same paddock in April. Only two lambs survived. Most lambs died between two and four weeks of age. There were no ewe losses and the owner considered that most of the ewes did in fact lamb.
(ii) 350 Merino ewes joined to Dorset rams from 20 December 1987, and put onto the flats during joining. A total of 128 lambs were marked, with more affected lambs born later in the landing period. These ewes were taken off the flats prior to lambing. In addition, 900 Merino ewes were joined to Merino rams, and 80 Merino ewes were joined to Dorset rams. These sheep were never on the flats and no cases were seen. No abortions were observed in the ewe flocks, there was no apparent increase in the proportion of non-pregnant ewes and there were no ewe losses. Weaner sheep grazed on the flats with no losses or ill-effect. Cattle on the property did not graze on the exposed flats. They calved in July-August with no cases observed.
It was speculated from this, that grazing of the weeds in early pregnancy exposed the foetus to some toxin which caused developmental abnormalities of the biliary tree.
The symptoms of 'white scours' and wasting can be related to these abnormalities and failure of bile secretion. Bile is an important aid in digestion and absorption, being involved in the activity of pancreatic lipase, and amylase, fat emulsification, fatty acid absorption and fat-soluble vitamin absorption.
When bile does not enter the intestine, fat absorption is diminished and the other food constituents become coated with fat or fatty acids.
Voluminous, fatty faeces and wasting of the subject, due effectively to malnutrition, result.
Three months later in early September 1988, a case of 'white scours' affecting Hereford claves was reported on 'FV' Wee Jasper, a property which also adjoined the Burrinjuck Dam in the upper reaches on the course of the Goodaradigbee River. Calves were generally about two weeks old when sickness was noticed and the course of the sickness until death was one to two weeks. Scouring calves became dopey, recumbent and, like the lambs, were strikingly jaundiced. There was a greasy, grey soiling of the hind legs, the liver was enlarged and fibrosed, gall bladders were small in some and grossly enlarged in others. Kidneys were olive green.
A total of nine out of 47 calves died from this condition.
Histopathology of the calves was similar to the lambs with an absence of mature, patent bile ducts and abundant fibrosis throughout the liver.
It is significant that only calves whose dams grazed exposed flats during early pregnancy were affected on this property. 30 Santa Gertrudis cows joined at approximately the same time, but not grazed on waterfront land, had 16 normal calves with no losses observed.
Breeding ewes on the property did not have any access to the flats and no losses were observed.
Two mares on the property which would have had access to the exposed flats, foaled in October and November 1988 with no problems noted.
A number of possible aetiological agents were considered in this outbreak. The occurrence of the disease in both sheep and cattle of mixed breeds eliminated the possibility of an inherited defect.
Similarly, there was no evidence of an infectious agent being involved. In addition, there was no evidence of any disease in the ewes, cows or other stock grazing on the affected properties. On the epidemiological information available, the most likely cause was considered to be a toxic insult to the foetal biliary system in the early stage of pregnancy. The toxic insult could have been due to a toxin that passed directly through the placenta, or a toxic metabolite produced in the liver or foetal biliary system. Such a toxin apparently had no clinical effect on the dam.
Investigations are continuing to identify the various plants growing on the flats during summer and subsequently to identify the particular plant by means of feeding trials.
I wish to acknowledge the specific collaboration of Peter Harper and John Plant of Glenfield in this investigation.