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This article was published in 1946
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Carbon Tetrachloride Poisoning
FURTHER OBSERVATIONS WITH PARTICULAR REFERENCE TO THE NUTRITIONAL PLANE.
D. J. WALKER, B.V.Sc., Inspector of Stock, Cooma.
In the 1945 Year Book of the Institute the role of the nutritional plane in mortality following drenching with Carbon tetrachloride was discussed briefly and three consecutive case histories recorded.
Since these mortalities were observed five others have occurred and additional information has come to hand. Of these, four support the suggestion that a rising plane of nutrition may be related to toxicity. The fifth does not appear to support it.
Case 1.—On the 17th August, 1945, 120 wethers were mustered from an 1800 acre poor, rough lease, all slate country, and yarded overnight in a small, fairly well eaten out lucerne paddock. They were drenched on the 18th and driven 200 yards to be turned back into the lease. Weather was reasonably warm, slightly rainy; and the sheep in strong store condition. At least 25 head died.
On the 20th August between 60 and 70 wethers were mustered from a thousand acres of lease similar to the above, drenched and driven about 300 yards to be turned back into the lease. At least five or six died.
In both these leases there was a definite early spring growth; similar country being carefully inspected after visiting the property. "Monkey Tussocks," a very coarse tussocky grass which was the principal feed, were showing marked new growth which the sheep were eating. Doubtless there was other feed in the leases because from about the 9th-16th August, and possibly earlier, wattle had been coming into bloom and willows greening. In addition, the leases being fairly well timbered carried feed which was sheltered from the frosts.
Five other mobs were drenched; 200 wethers on the 22nd, 250 ewes on the 29th, 250 two-tooth on the 28th, and 250 weaners on the 7th August. Out of all these only one sheep was known to have died. In each case the sheep were running on country which had been improved by ringbarking and carried much better feed; a high proportion of this being dry.
Case 2.—A mob of 250 ewes. mostly full-mouthed, had been running on a hill paddock of granite formation where there was a fair sheep pick. Feed was improving after February rain. The mob was moved for a few days into a paddock, light basalt in type, which during the previous winter was under oats. This paddock carried a fresh growth of feed, principally barley grass. It had not recently been stocked.
Before drenching, the sheep were moved into yards, allowed to spell and, after drenching, moved a short distance to a similar cultivation paddock. The loss was about 20 head.
Case 3.—A mob of 490 five-year-old ewes and 330 six-year-old ewes were drenched. Approximately 75 died; with one exception being five year old ewes.
On about, 8th March, 1946, the six-year-old ewes were very poor and were moved from sparse dry feed on to ample oat stubble, carrying in addition a good body of fresh, young feed; mainly barley grass.
On 8th March the five-year-old ewes were running on poor feed; the owner describing the paddock as very bare. They remained in this paddock till delivery. All country on which the sheep had been running was basaltic.
On 29th March the sheep were delivered to a new owner and driven a total distance of 16 miles on that and the next day over roads which were relatively bare. On arrival at the new owner's holding they were placed for twenty-four hours on an alluvial carrying fresh lucerne, barley grass and corkscrew in fair bulk. On the 2nd April approximately half the mob was removed from the paddock and drenched. Next day the other half was drenched and the sheep commenced travelling by road. Losses started within 24 hours and continued for ten days.
90 sheep which were running continuously on the holding were drenched without ill effect.
Case 4.—It was not possible to investigate this mortality thoroughly. Briefly, a small mob of some two or three hundred sheep were drenched, some of the sheep at the time being affected with photosensitisation.
From personal knowledge of the locality it was known that trefoil, barley grass, native grasses and herbages were growing very rapidly at the time, and feed was improving fast on the alluvial flats of basaltic origin on which the sheep were running.
Case 5.—About four months after a loss following drenching, the owner supplied the following information: 340 grown wethers had been running in open, rung, granite country for six months prior to drenching. They were taken from the paddock, drenched, shedded overnight on account of threatening weather and let out for about two hours into a smaller paddock, which carried the same type of feed as that from which they were moved. 40 head died, losses commencing within twenty-four hours.
This case would appear to discount the suggestion put forward. However, the time elapsing between the information being made available and the mortality would allow ample scope for inaccuracies.
Discussion: With the exception of Case 5, in each of the mortalities reported in this present Journal and in the 1945 issue there had been a rising plant of nutrition. What may be of more significance is the fact that in each case there had been a recent increase in the amount of green feed available.
Mortality had occurred on the richest and the poorest country.
An attempt was made at the Glenfield Veterinary Research Station to induce tetrachloride poisoning. The official report of the experiment circulated to each Inspector in his District by the District Veterinary Officer, South East, at whose suggestion the trial was made, showed that the suggested relationship of improved nutrition was not confirmed.
Though this does not support the theory advanced, neither does it disprove it. Though insufficient data is available at present to draw the conclusion that mortality following drenching only occurs in this District when sheep are on a rising plane of nutrition, there appears to be some promise of being able to point out to graziers how they may avoid the main risk in this area.