ARCHIVE FILE
This article was published in 1946
See the original document
INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
An Unusual Type of Mortality in Cattle
(ATTRIBUTED TO ROCK FERN)
T. R. JONES, B.V.Sc., Inspector of Stock, Forbes.
About 20th March, 1946, the writer was informed of a mortality in cattle. The owner stated that he had some 80 head of cattle running on some mountain country for from six to twelve months; and as they appeared to be doing well he decided to bring them to his home country to finish them off for market. The country where the cattle were running was fairly rough and only 68 head were mustered, left in a gully for a day or so and then brought in about 20 miles to the home farm. When they were collected from this gully one vealer was seen to have a black scour and died before they left; while another vealer died within five hours of arrival on the home country. It had taken sick on the road and was said to have been passing blood. Seven animals died in as many days after arrival home; all with the same history. The animal would appear to be sick for a day or so—develop a black scour—and die with very little struggling. The owner was informed that the mortality probably was due to Rock fern poisoning, and that mortalities probably would cease within a few days. No suggestion was made as to treatment.
Losses continued spasmodically among vealers and cows and in ten days about 10 had died; after which the matter was investigated with the D.V.O. On arrival at the property two dead cows were found; one being still warm and suitable for post-mortem.
The following covers the examination made by the D.V.O.:—"A post-mortem examination was made of an old cow, in fair condition, which had died during the night; the carcase being still slightly warm. The following abnormalities were noted: Subcutaneous petechiae in places. A little blood-stained fluid in peritoneal and thoracic cavities. Extensive ecchymoses on both surfaces of the diaphragm and thoracic wall. These in places appeared to be more in the nature of sub-serous splashes. The lungs showed ecchymoses, both on the surface and in the tissue. The same were noted on both surfaces of the heart; these being more extensive externally. The liver appeared to be slightly brownish, with distinct patches of deep ecchymosis, and the gall bladder was enlarged. The bile appeared normal. Kidneys were normal in appearance though a bit tougher than usual. Urine appeared normal but there were odd petechiae on the bladder wall. The spleen was normal in size but the contents were somewhat pulpy. The rumen, omasum and reticulum appeared normal and the contents were fresh. The abomasum showed marked changes throughout; the anterior end being of a uniform dull red colour, with the lesions becoming more marked towards the pylorus. The stomach wall was thickened, there was extensive haemorrhagic ulceration and the contents were practically nil. Similar lesions occurred throughout the small intestine to a lesser extent, the contents being mainly blood-stained fluid. The caecum contained a mass of clotted blood, but was otherwise normal. There did not appear to be any lesions in the large intestine. All the thoracic and mesenteric lymph glands appeared congested and watery."
The owner stated that these post-mortem appearances were typical of those in other animals he had opened. Various specimens were sent to Glenfield Research Station for detailed examination and these confirmed the first diagnosis in the field; no organisms capable of causing the trouble being recovered.
By 3rd April fifteen (15) cattle had died, all apparently from the same trouble, in a period of about 16 days; although by now the sickness was prolonged to from three to four days. By 15th April, 18 bad died; the last case occurring on that day, when a cow and vealer were being driven to market. After being chased for about half a mile, this vealer refused to travel, appeared to be exhausted, passed a black scour and died in about 12 hours. On 24th April the property was revisited and the balance of the cattle appeared to be healthy.
Comment: Mortalities of this nature are encountered not infrequently in similar circumstances. Stock—both sheep and cattle— graze on hill pastures contaminated with Rock Fern with apparent impunity unless they are stirred up. This is quite easy to do as stock run under such conditions are inspected infrequently and so become fairly wild. Usually there is little feed in such country in the late summer and early autumn, and so the intake of Rock Fern under semi-arid conditions is probably greater than it is in times of plenty. Losses occur when the seasonal conditions are as stated and stock are raced about. Deaths may follow within 24 hours after excitement occurs, for example, after mustering—and may continue for 10 or 14 days after removal from the country or after being excited. If they are undisturbed nothing happens. In this particular case losses occurred for about one month after the preliminary excitement. Among the cattle left in the hills-12 in number—the only loss was one cow which was found dead a few days after a fox shooting party had been through the country where these cattle were running. This beast could have been shot, but the cause of death was not determined. The mortality described above is attributed to poisoning by Rock Fern (Cheilanthes tenuifolia).