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This article was published in 1949
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
INFANT LAMB MORTALITIES
G. CHARLES, B.V. Sc., Inspector of Stock, Carcoar.
Over the past two years the opportunity has been taken to investigate a number of mortalities in infant lambs on various properties throughout the District. So far the investigations have proved inconclusive, but certain observations have been made; and the whole matter is recorded as being of interest.
The lambs implicated in these outbreaks generally die within the first 72 hours of life, although a small percentage may be born dead. As this is mainly a fat lamb area, crossbreds predominate, but two cases have been encountered in Merinos. The mortality rate is variable and ranges from five to 80 per cent,: the avenge being of the order of 15 to 25 per cent.
With one exception the pastures all have been improved, and containing subterranean clover. The ewes all appeared quite healthy, were in good condition, had ample milk and were varying from eight to nine months' wool.
The post-mortem picture shows certain features which are present almost invariably. In a high percentage of cases, on opening the abdominal cavity a very obvious feature is the greatly distended urinary bladder with an inflamed wall, and containing up to 50 mls. of clear urine. The urethral opening is patent in all cases, as moderate pressure on the bladder results in the flow of urine. The kidneys show no gross changes but the kidney fat is red in colour and in some cases slightly gelatinous. The ureters show inflammation of the distal end, probably spreading from the bladder wall. The omentum is haemorrhagic, and the small fat deposits resemble blood clots. The mesenteric lymph glands are enlarged to about bean size, and are somewhat oedematous. The spleen in usually normal in appearance, but occasionally shows pinpoint haemorrhages along the free margin. The gastro-intestinal tract is always empty, save for the meconium.
The thoracic cavity usually contains about 10 mls. of slightly blood-stained fluid. The lungs may be aerated or not, but are otherwise normal. The pericardium contains at least 5 mls. of clear fluid while the heart is flabby and engorged, with a few subrepicardial petechiae. The thymus and thyroids appear normal.
Complete sets of specimens, from a number of lambs have been submitted to Glenfield for examination, but with the exception of two cases—from different properties—nothing could be found. In the two eases mentioned, Bact. coscoroba and Bact. neapolitanum were isolated; but blood sera from the ewe concerned showed no appreciable level of agglutinin titre for these organisms.
Regarding the above organisms, the D.V.R. advised: "These two organisms are strain types of the coliform group. They may be regarded as specific variants of the classical Bacterium coli. As such they occur primarily as normal flora of the intestinal tract and occur wherever faecal contamination has taken place. They are not normally soil saprophytes, although they frequently may be isolated from soil. Occasionally strains of enhanced virulence in either cause infections on their own count or appear as agonal invaders in various animals."
During the lambing season just completed, certain observations were made regarding the husbandry of the ewes, and this led to a theory which it is hoped to prove or disprove next lambing. Firstly, it was noted in all flocks in which the trouble occurred that the ewes were carrying large quantity of wool along the lower edge of the flanks, and this, in many cases, hung down to within six inches of the ground. This rendered it almost impossible for a newborn lamb to reach the udder, as it could not lift the weight of the wool high enough. Following on this, lambs were seen to suck the "sweat dags" inside the ewes' thighs, apparently in an effort to satisfy their hunger, and it is thought that this is where the bacterin, isolated from the two cases, gained access to the gastro-intestinal tract. Once there, they multiplied rapidly, invaded the blood-stream and so reached the various organs from which they were cultured. Thus, while the bacterial infection may play some part in the death, it is considered that most cases result from actual starvation, and that the constant feature of an empty gastro-intentinal tract tends to substantiate this. On two properties arrangements have been made for the wool to be removed from the lower edge of the flanks at the pre-lambing crutching of the ewes, leaving some untreated for comparison in order to check this theory.
ACKNOWLEDGEMENT
The unfailing co-operation, cheerfully given, of Mr. Jack Rowlands, "Werribee," Waugoola, and Mr. Bert. Witheford, “The Pines," Neville, is gratefully acknowledged. Thanks are due also to Mr. J. N. Henry (D.V.O. West) for permission to quote from official files.