ON THE LAND

Taranaki Daily News, 13 October 1934, Page 24 (Supplement)

ON THE LAND

LIVESTOCK POISONING JTHE CAUSES DISCUSSED POISON FROM PLANTS. The recent death of four young heifers, two of them pedigrees, on the New Plymouth Boys’ High School farm through poisoning has again drawn attention to the danger to stock that arises from leaving about old tins that have contained, paint. In this case the authorities were not in any way to blame as the tins which the cattle picked up had been thrown into the paddock gome years ago, before the school secured the property. That, however, only further emphasises the need for care as owing to its oily nature paint will remain a potent source of danger for ■. years. , ' . kt In the September issue of the NewZealand Journal of Agriculture appears a paper read before the New Zealand Veterinary Association by Professor B. C. Aston, chief chemist of the Department of Agriculture, embodying the result of over 30 years’ experience in investigating suspicious mortality in livestock with a view to the detection of . poison in the animal or the food upon which it had fed. It may be accepted that domestic stock, including animals of all kinds, poultry, fishes and invertebrates, such as bees may be the subject of inquiry, and these may have eaten or otherwise absorbed * poison which caused their deaths, and that these phenomena may be conveniently classified under four headings, chosen for the sake of convenience rather than on any strictly scientific ground: (1) Inorganic or mineral poisons or preparations used for destroying unwanted forms of life,’’ (2) indigenous poisonous plants, (3) wild exotic poisonous plants, and (4) cultivated exotic poisonous plants. ~ , . Under the first heading should be included all poisonous metallic compounds such as those of arsenic, lead, antimony, phosphorus, mercury, as well as of organic compounds such as the cyanides end dydrocyanic acid, strychnine, etc., frequently used in agriculture as animal poison, plant fumigant, or weed-killer. Arsenic compounds are largely used as weed-killers. Lead compounds, as paint, are most deadly in the shape of old paint tins containing some of the moist paint, also recently painted fences, gates or even houses. Recent paint is especially attractive to cattle on account of the linseed oil with whith the paints are mixed. Phosphorus is largely used for rabbit poison, and the cyanides for fumigating greenhouses, while strychnine is more and more used in certain seasons for killing, rabbits. Caustic preparations are used in cleaning dairy apparatus; and it appears almost certain that the effluents running in open drains in dry weather may be consumed by stock, and if containing sodium hydrate or carbonate are injurious in proportion to the amount consumed. Excessive doses of salt such as may be found in kitchen refuse may ba fatal to pigs and poultry if fed to those animate. INDIGENOUS POISON PLANTS. ■ The poisonous native plants of New ' Zealand, although comparatively few in number, are a most decided menace to stock-owners where there is any rough or virgin or partially broken-in land, or where the animate are driven through such area. Poisoning by several New Zealand plants is more insidious, as some of them are, in limited amounts, beneficial in so much as they are undoubtedly highly relished and are good grazing material. It is only when the animate are driven or starved or are ravenous for a change of diet that they consume such large quantities that poisoning occurs.

An endeavour is made to place these New Zealand native plants in the relative order of importance: (1) Coriaria (3 and 4 species), tutu or tupakihi; (2) Pteridium aquilinum, bracken or fern; (3) Myoporum laetum, ngaio; (4) Pimelia (several species), Strathmore weed; (5) Brachyglottis rangiora, rangiora; (6) Urtica ferox. onga onga or tree nettle; (7) Wintera (Drimys) axillaris, horopito or pepper tree; (8) Hydrocotyle asiatica, pennywort; (9) Edwardsia (Sophora) tetraptera (several species), kowhai; (10) Ranunculus rivularis (swamp buttercup), waoriki; (11) Dianella intermedia, turutu; (12) Euphorbia glauca, waiuatua; (13) Parsonsia (2 species), kaiku; (14) Cdrynocarpus laevigata, karaka. The first four plants are undoubtedly responsible for stock poisoning from time to time, mainly the result of an abnormally low natural food supply or a too restricted diet of an artificial kind. There is no doubt as to the poisonous nature of all four in New Zealand, and this is supported by what might be called their family history—that is, the known effects of closely allied plants in other countries. In the - case of fern, stock are often crowded on to young grass country where the young fem is coming through in order to stamp and eat it out and no doubt experience poisonous effects in addition to starvation. , The tutu (Coriaria sp.) is the most historic poisoning plant of New Zealand, as Captain Cook lost the first animals he introduced by “toot” poisoning, as it is called by the settler. Dr. Lauder Lindsay states that in the early days those colonists were fortunate who had not lost 25 per cent, of their stock through tutu poisoning at the time of his visit (1861). Like another poisonous plant, sagwort, tutu in one of its forms is greatly relished by sheep, at times forming no inconsiderable part of their diet on rough hilly country. Cattle may also eat it in moderation, but when driven or when hungering for a change of diet, such as after being on a turnip paddock, they quickly succumb to large quantities of tutu ingested. This appears to be the case with all kinds of herbivores which 'will eat it, but it must be noted that no case in horses has ever been reported, and presumably it is distasteful to that animal. BRACKEN FERN POISONING. The next most common source of poisoning from plants is that occasioned by the New Zealand bracken fem (Pteridium aquilinum), variety esculenta, the roots of which were the staple farinaceous food of the primitive Maori. The above-ground parts are undoubtedly poisonous, and one American investigator of the bracken there showed that a drug habit was acquired by horses eating the fem, so that when stall-fed they ate their own bedding of bracken in preference to good hay. Exact feeding experiments have also been carried out in Great Britain and the poisonous nature of the English bracken fully demonstrated.

Myoporum laetum (the ngaio). the well-known coastal tree, undoubtedly causes a large number of deaths in cattle every year, especially in the stormy winter season, where large limbs or trees are blown down into the paddocks and enable leaves, fruit, and branchlets to be reached by the cattle, which, possibly owing to shortness of feed at that time, greedily devour sufficient of the plant to cause poisonous symptoms.

This is the time of the year when the fruit is ripe. . There are several species of Pimeha in New Zealand. Cheeseman in the Manual of New Zealand Flora records as many as fifteen species, but there may be several more, as the genus. has not been critically studied. It is known jn New Zealand generally as Strathmore weed, from the name of a Taranaki town where poisoning of horses was first recorded. The genus is confined to Australia and New Zealand. In Queensland several species are suspected of poisoning sheep. The genus Pimelia is closely allied to Daphne, a species of which are so much grown in gardens for the ornamental scented flowers produced. Dapime supplied a vesicant to medicine under the name mezereon bark, and the Pimelias have a similar action in causing blisters and burning sensation in the mouth when chewed. This sensation persists for some time, and is a common symptom resulting from every species the writer has tasted. New Zealand cases of poisoning recorded relate largely to horses. A dry resinous mass which was extracted by volatile solvents from Pimelia bark by the writer was poisonous to guinea-pigs. Some cases are recorded by Mr. Webster, in the Wairarapa. A case of mortality in calves which occurred at Te Kuiti in October, 1928, wps probably due to leaving travelling stock (calves) in a starving condition in a paddock in which there was little else but Pimelia. In any case where veterinarians find as a symptom blisters in the mouths of stock they would do well to seek the evidence of the ingestion of one of the species of Pimelia, all of which are found on stony or sandy waste land and often by roadsides where driven hungry stock are allowed to pasture. The rangiora (Brachyglottjte rangiora) belongs to the largest botanical family of flowering plants, the Compositae, which contains all those plants producing “daisy” flowers. Although a common plant, the rangiora te but rarely suspected of poisoning stock. Baber (1886) states that this shrub is seldom eaten by cattle or sheep, but that horses are very fond of it. The effect on animate is said to be a staggering of the legs and falling. Skey (1881) failed to recognise any poisonous principle from Brachyglottis. The poisonous nature of some wild honey has been attributed to nectar from rangiora. The drunken condition of horses after eating rangiora leaves is stated by farmers to be curable by briskly exercising them. Etedon Best reported that horses are supposed to be “wharangied” when poisoned by the rangiora, “wharangi” being another Native for the shrub. Blood-letting and violent exercise are the Native cures. His own horse had been “wharangied,” and had to be taken for a three-mile sharp canter to cure it. The ■ stimulating nature of the rangiora poison te interesting in view of the fact that the imported ragwort belongs to the same family, and te highly poisonous to cattle and horses but less so to sheep, for which it is, in moderation, a useful fodder. In connection with the prominent symptom in horses—staggering— it te of interest to note that one of the English trivial names te “staggerwort" Apparently, from the observation of farmers, cattle and sheep are seldom poisoned by rangiora, although they are known to eat large quantities of the leaves. Urtica ferox (onga onga or tree nettle) carp*: were reported where this unpleasant looking plant had cause the death of horses and dogs.