Plants Poisonous to Stock

New Zealand Journal of Agriculture, Volume 71, Issue 3, 15 September 1945, Page 229

Plants Poisonous to Stock

By

D. H. LeSOUEF,

B.V.Sc., Veterinarian, Wellington.

ANY general lessening of greenfeed during cold spells when growth is at a low ebb entails the possibility of stock being poisoned by the consumption of plants not normally eaten. In general animals that are likely to be affected are those more than normally hungry, such as travelling stock, those placed in unaccustomed fields with sparse herbage, or the odd horse or cow that is a forager with a tendency to break through fences or get into the garden. : Trees and other plants that are known to have caused trouble or deaths are set out below, but symptoms cannot always be observed or treatment given, as in many cases the animals are found dead or “in extremis.”

THERE may be other poisonous or suspected plants in New Zealand, but the list which follows covers the main ones.

Bracken Fern

Bracken fern (Pteridium esculentum) is a common fern throughout the country, and consists of a starchy underground stem or rhizome with rootlets attached and fronds springing up at intervals, being soft and tender at first but soon hardening off. Cattle are often put on to country after a burn when the fern is young, to help trample it underfoot and break down the growth, and it is at this stage that trouble usually occurs. Poisoning may take place in about a month on country which is growing little else, and the symptoms shown are emaciation and anaemia, indicated by the pallor of the mouth and eye membranes; then blood is passed and in the final stages coma occurs, with death supervening after 12 to 72 hours after ' onset. of the symptoms. The poison seems to be cumulative and small quantities may be taken for some time before the symptoms appear; 61b. per day has killed in about a month. (1).

Satisfactory treatment is not readily given, as the stock usually affected are young or run stock, but a purgative followed by a complete change to good pasture with supplementary food may save beasts in the early stages.

Strathmore Weed

Strathmore weed (Pimelea prostrata) is a common plant in the North Island, and belongs to the same family as the garden daphne, having wiry, straggling, much-branched stems, short leaves, and terminal clusters of whitish flowers. Horses are reported to have been poisoned by this plant, the symptoms in severe cases being narcotic effects or convulsions. The bark and berries especially are acrid and poisonous (1).

Hemlock

Hemlock (Conium maculata), sometimes called carrot fern, is a biennial plant having fern-like leaves of a dull green, blotched with brownish-purple, as are the hollow stems. The flowers occur as white umbels and may shoot up 5 or 6ft. in height. The plant has a strong foetid smell and contains a poison (conine) which is a narcotic alkaloid. Stock rarely take the plant, but have been known to do so when shut in a small enclosure in which the rank plants were growing. Symptoms noted have been sluggishness, difficulty in walking, and paralysis; coma and death follow. A heifer suffering from hemlock poisoning some years ago is known to have recovered after a purgative drench of Epsom salts and ginger in the early stage of the disorder.

Juniper The juniper (Juniperus sabina) comes under the heading of garden clippings, as do the laurel (Prunus, several species), privet (Ligustrum vulgare), yew (Taxus baccata) and rhododendron. Particular care must be taken when cleaning up old-established gardens that stock are kept away from the rubbish heap until, it is completely destroyed by burning. Valuable dairy cows have been lost by eating such clippings. Symptoms in cases of poisoning through eating the above-mentioned clippings have been rather similar. Constipation, slimy foetid faeces, staggering,. and distress, and sometimes bloating have been evident. Death occurs within a few hours.

Karaka

Karaka (Corynocarpus laevigata), a handsome native tree with shiny darkgreen leaves, is grown in gardens in many parts. The fruit is soft and yellow with a strong pleasant smell and a very hard woody centre containing a whitish seed. This seed has sometimes been eaten by dogs which have been chewing the stone, and its poisonous properties have caused

sudden death. These properties are destroyed by heat and the cooked seeds were -used by the Maoris for making a flour. Macro car pa. Abortion has been caused in cows after eating shoots of macrocarpa (Cupressus macrocarpa), as was reported in the “Journal” of October, 1943, by Messrs. Gilder and Alexander. All the animals affected were cows close to calving (about ‘ 8 months pregnant) and they had been placed in paddocks containing fallen limbs of this tree. Ngaio Ngaio (Myoporum laetum) is a native and common throughout New Zealand, chiefly by the sea coast, being hardy and quick growing. Cases of poisoning have been reported in cattle, sheep, and pigs that have eaten ngaio foliage. The writer has seen several cases where up to six cows on one property have been lost, the owner suspecting malicious poisoning by his neighbours. The symptoms noted in cattle were pain and distress followed by bloating and dullness; death occurred within less than a day in most cases, although some beasts lingered for a few days. Sheep and pigs have been poisoned with the leaves, but usually a whole tree . or large branch that has been blown down has been the cause of the trouble with cattle. Feeding experiments have recently been carried out at the Animal Research Station, Wai-

laceville, by Drs. I. J. Cunningham and C. S. M. Hopkirk, and full details have been published (2). The Tasmanian variety of ngaio (Myoporum serratus) has also been proved poisonous to sheep. The writer has not been able to give treatment in time, nor have others reported any success, so that stock owners are advised to take precautions after a wind storm by seeing that no stock have access to broken ngaio branches. Nightshade The black nightshade (Solanum nigrum) is a ' very common weed of cultivated land and odd corners of domestic gardens. It has even been cultivated and used for jam making. It is often misnamed the deadly nightshade, which is a very poisonous member of the same family rarely, if ever, found in New Zealand. Poisoning by the black nightshade has been reported only in one or two instances, symptoms being stupefaction and staggering. Sheep penned in a small paddock with no other herbage in it have died through eating it. Stock eating sprouted potatoes (Solanum tuberosum) have shown similar symptoms, and horses have died when fed sprouted potatoes mixed with grass (3). Ragwort Ragwort (Senecio jacobaea) is a (2) A. J. Healy, ' N.Z. Journal of Science and Technology, Vol. XXVI. (3) W. A. Dickinson, Vet. Record., Vol. IX, No. 42. '

well-known weed and the bane of many a property owner’s life. Its consumption by stock causes Winton disease. It is distinguished by its fern-like leaves and brilliant yellow flower heads, which in summer time may be seen covering large areas in some districts. Poisoning occurs in horses, cattle, and sheep, and symptoms may appear in a month and up to six months after the stock first graze on the . plant. A falling away in condition, capricious appetite, and brain symptoms such as paddling with the feet and walking into things as though unconscious of the surroundings are noted, especially in horses. There may be constipation or diarrhoea, with evil-smelling faeces. Death may supervene in a few days or more after the first symptoms, and a postmortem examination reveals a pale, hard, fibrous liver with inflammation and oedema of . the bowel. These symptoms are shown in both horses and cattle and often appear after the animals have been moved off the ragwort country to good pastures. Sheep can be affected but are slow to show the symptoms and, as with cattle, they will start dying a short time after being moved off the ragwort. There is no successful treatment generally known once the symptoms have appeared, although success has been claimed in some cases. Poisoning may be caused by eating the plant in the young rosette stage, the flowering stage, or when the weed has been cut

with the pasture and fed dry in the form of hay. Stock will not eat the growing plant if there is sufficient other feed about, hence eating usually takes place in the autumn and winter, though the symptoms do not show up until spring. t Prevention by destroying the plant - with sodium chlorate, pulling or cutting and burning is the best cure.

Rangiora Rangiora (Br achy glottis repanda) , a well-known . native shrub with' large green leaves, having a soft white under surface and clusters of a tiny whitish flower, has caused poisoning at' times, but apparently only when in flower (1). The honey gathered from it is also poisonous. Symptoms noted in horses and cattle are staggering, as though tipsy, and then lying down. Death occurs without a struggle. Recovery may take place after ' the first symptoms have appeared, and although no proved treatment is known, sharp exercise and a good purgative are to be recommended.

Buttercup The celery-leafed variety of buttercup (Ranunculus sceleratus) is an annual found in damp pastures and ditches, and has a tap root with a stem up to a foot high, the stem and leaves being somewhat like those of celery. The leaves are bright green, three-lobed, and shiny, with flowers a quarter of an inch in diameter and yellow in colour. The plant is decidedly poisonous, causing vesicles by burning the mouth parts and stomach. Fortunately the acrid taste causes stock to avoid it in most cases, but some cattle will develop a craving for it and eat sufficient to cause death. The plant has caused losses in the Wellington and Nelson Provinces within recent years.

Cape Tulip The one-leafed cape tulip (Homeria collina) has recently been found in New Zealand (2) as a garden escape, although it has been known in South Africa and Australia for many years as a dangerous plant. It belongs to the same family as Watsonias, etc., and has a single leaf 1 to 2ft. long and i to Jin. wide, and a single stem shorter than the leaf, bearing 2 to 4 clusters of flowers of from orangescarlet to salmon pink in colour. The plant is very poisonous, and the symptoms are described by Clarke in Australia (1939) as intense gastrointestinal irritation and bloating. Death usually occurs in 12 hours, though some cases linger a few days.

Tutu Tutu (Coriaria arborea), found on the margins of forests and on rookyfaces throughout New Zealand, has young shoots which are soft and fleshy and more likely to be eaten than the adult plant which forms a tree, with hard woody stems. This plant again is one that is eaten only when stock are very hungry, say after droving in the summer time in the back country. The onset of symptoms is rapid, with violent struggling and running followed by bloating. Treatment is of little avail, but bleeding by cutting the ear or tail is often resorted to with dubious success.

(1) B. C. Aston, Journal of Agriculture, Vol. XXVI.