POISONING OF LIVE-STOCK.

New Zealand Journal of Agriculture, Volume XL, Issue 6, 20 June 1930, Page 386

POISONING OF LIVE-STOCK.

SOME COMMON MINERAL AND PLANT POISONS

C. V. Dayus,

M.R.C.V.S., District . Superintendent, Department of Agriculture,

Dunedin.

It is by no means an easy matter to clearly define a posion. A common dictionary definition of the word is “ that which is noxious to life.” Guy states : "A poison is any substance or matter (solid, liquid, or gaseous) which when applied to the body outwardly, or in any way introduced into it, can destroy life by its own inherent qualities without acting mechanically and irrespective of temperature.”

But there are many poisons that may do considerable harm without necessarily causing death. Lander gives another definition : “A poison is some substance which is acquired by the body in comparatively small amounts with harmful results, sometimes with death as a sequel.” Gould’s definition is : “A substance that being in solution in the blood or acting chemically on the blood either destroys life or impairs seriously the functions of one or more of its organs.”

Strictly speaking, bacterial toxins, snake-venom, &c., are poisons, but it is not intended to attempt to discuss these in this article, which will be confined to the common mineral and plant poisons met with in New Zealand.

The location of the absorption of a poison has a distinct bearing on the degree of its effect. Poisons may be absorbed by any portion of the natural food-tract, by the respiratory tract, or through the skin. The food-tract is the most usual place for absorption to take place, chiefly through the stomach and intestine, on account of the more delicate lining membrane of these parts. As a general rule materials insoluble in water, in dilute acids or dilute alkalis, are not poisonous by the food-tract. This fact is observed in the selection of antidotal treatment, when materials are often given for the reason that they tend to render the specific poison less soluble.

Soluble poisons are easily absorbed by the respiratory tract, which is a very suitable channel: if they acquire contact with it. The intact skin is generally an effective barrier against absorption, but the broken skin, such as small abrasions, wounds, &c., is quite a different matter. The appreciation of this point is an essential one on account of the extensive use in New Zealand of dipping and spraying fluids for lice and ticks. The majority of such fluids are roughly solutions of arsenical preparations or coal-tar derivatives with the addition of an alkali.

The addition of an alkali, while essential for the effective operation of the dip or. spray fluids, also increases the penetrative powers of arsenic and phenols, and this is especially so if the solution is too strong. The reason for this addition is that the alkali saponifies and emulsifies the fatty nature of the normal skin secretion — is, it converts it into a soapy emulsion.

If a poison does not actually destroy tissue, and cause death by shock it does not exercise its effect until it has entered the general •circulation. By this means it has 'to pass the natural barriers the

liver and ■ lungs. The liver arrests most metallic poisons and, many alkaloids. An alkaloid is a nitrogenous compound occurring in plants, and generally the active principle. Many poisons, notably metallic poisons, since they are arrested in the liver are cumulative. But following the absorption of most poisons elimination is more or less rapidly commenced by the excretory channels of the body. The well-known maxim “ What is one man’s food is another man’s poison ” serves to emphasize the rather important question of tolerance. In the case of some poisons an immunity may develop as the result of repeated small doses. Then there is the variation of tolerance in the different species to the same poison. For example, the ox is more sensitive to lead than the horse; but generally speaking the ruminant animal is more resistant to poisoning than the horse, dog, and cat. The action of morphia is well known : it induces stupor. In the cat, however, it has the exact opposite effect —an idiosyncracy not easily explained.

Poisons are roughly divided into the following classes : ' (1) Corrosives, such as the strong mineral acids, caustic soda, perchloride of mercury, carbolic acid in strong solution, &c. They act by actual destruction of the living cell. (2) Irritants, such as arsenious acid (white arsenic), acetate of lead (sugar of lead), subacetate of copper (verdigris), sulphate of copper (blue vitriol, bluestone), silver nitrate (lunar caustic), bichromate of potassium, aloes, croton oil, &c., producing vomiting,. delirium, &c. (3) Narcotics : Drugs producing stupor, mostly drawn from the vegetable kingdom, such as opium, hydrocyanic acid (prussic acid), alcohol, chloroform, ether, chloral, &c. (4) Narcotic irritants, forming a very large class, such as strychnine, foxglove, saffron, deadly nightshade, tobacco, yew, &c. .

The poisoning of animals is generally brought about by their acquiring the poison by means of food and water, and occasionally through the broken skin. Cases of arsenical poisoning have occurred through dipping and spraying in both cattle and sheep. The fluid may have been allowed to drip from the animals and so contaminate foodstuff. Again, the directions on the makers' containers may not have been strictly adhered to. Poisoning of cattle has followed spraying them with some sheep-dips, in spite of the fact that the directions have specifically stated that on no account must the fluid be used for dipping or spraying cattle, horses, or dogs.

It must be borne in mind that sheep-dip solutions are as a rule much stronger than similar solutions used for cattle, horses, or dogs. This is so on account of the necessary penetration of the wool, and is possible with no attendant danger because sheep do not lick themselves. The majority of cases of mortality after dipping are due to defects in the process, including the following: (1) The dip is not made up according to the accepted strength as advised by the makers ; (2) the dip is not stirred properly ; (3) sheep are put through too quickly ; (4) too long immersion ; (5) sheep are driven before dipping or too soon afterwards, or dipped on a full stomach. It is necessary to exercise great caution with dipping-fluids, as they are all poisonous ; the trade designation “ non-poisonous ” applied to

some fluids is a fallacy. Many of the well-known proprietary dips are of standard uniform strength, are in universal use, and every safeguard is taken against any danger attendant upon their use, providing strict attention is paid to the directions, and the method of procedure carried out judiciously and correctly. Lead poisoning is by no means uncommon, due to animals having access to freshly painted structures, and through old paint-tins and white - lead containers not being carefully disposed of. Cattle are notoriously inquisitive, and paint seems to have some added attraction for them. Lead shot from opened cartridge-cases has also been known to be responsible for poisoning. The use of poisons to control vermin, notably those containing strychnine and phosphorus, accounts for some cases of poisoning of domestic animals.. Caustic soda for cleaning dairy utensils has accounted for mortality, notably in pigs.

One of the commonest plant poisons is ragwort, due to continuous ingestion of the plant in districts where the natural pasture is extensively invaded by it. Another is tutu, which is not readily eaten unless the. animal is suffering some degree of starvation—for instance, after being driven. A further instance is buttercup poisoning. . Careless disposal of clippings from garden . shrubs and plants is a source of trouble sometimes ; they should always be regarded as unsafe. Poisoning from this source may be due to laurels, rhododendron, laburnum, yew, &c. . • . The amount of poison acquired naturally regulates the course which follows, and poisoning may be acute or chronic with possible intermediate degrees. In acute poisoning the symptoms are quickly noticeable and intense, with a rapid course and early termination. In chronic poisoning the result is produced by the cumulative effect of repeated doses, as, for example, in ragwort poisoning, though as a general rule cases of chronic poisoning are not common in animals.

Some of the Common Poisons

Lead. — The source of lead has already been indicated. An oxide of lead commonly known as red-lead is used in painting and plumbing. A basic carbonate known as white-lead is used as a pigment. The cases of poisoning met with are commonly in cattle. The main symptoms of acute lead poisoning are gastro - enteritis, derangement of the nervous system, twitchings and convulsions, salivation and nasal discharge, and later blindnessan animal will stumble into any available obstacle ; temperature nearly normal or below normal; coldness of the extremities, followed frequently by collapse, coma, and death. In chronic lead poisoning, called “ plumbism,” in the. human subject, which is of rare occurrence in animals, a characteristic'blue line appears on the gums, with general digestive derangement.' In cattle evidence of paint is frequently found after death in the third stomach, commonly known- as the "book” or '"bible.” In treatment the primary step must be to stop the source of supply. Epsom or Glauber salts should be given ; . these are the sulphate of magnesium and . sodium respectively, and by chemical action either tends to form lead .sulphate,

which is insoluble. Bulk doses of tea or coffee with milk should then be given and the animal kept warm. Arsenic. — dipping-fluids the alkali arsenite employed is generally sodium arsenite, which is easily soluble and the most poisonous of the ordinary arsenical preparations. The general symptoms of arsenical poisoning are salivation, thirst, colic, and a subnormal temperature with trembling, stupor, and convulsions. Death takes place sometimes very rapidly. There is a very marked stiffness in movement almost amounting to paralysis, especially of the, hind limbs. Often portions of the skin assume a characteristic purply - blue colour, especially noticeable round the udder in a cow ; later this area may undergo sloughing. This is comparable to arsenical eruption noted in man.

The chemical antidote is freshly prepared ferric hydroxide (an iron compound). In addition milk, white of egg, and lime-water in large quantities are useful. Phosphorus. Yellow phosphorus is the form met with in verminpoisons. In New Zealand it is used in the manufacture of phosphorized pollard for rabbit-destruction. A peculiarity is that symptoms may be delayed some hours, even days after 'taking, as it is slowly absorbed. The symptoms are those of intense thirst and abdominal pain. Possibly the breath may be luminous in the dark. In pigs I have found free phosphorus in the stomach-contents several hours after death. Bluestone is given as an antidote, it being supposed to remove, the poison in the form of copper phosphide. In phosphorus poisoning any oils, milk, or anything of a fatty nature should be carefully avoided.

Strychnine. Strychnine is one of the two chief alkaloids of the seeds of Strychnos nux vomica, an East Indian tree. The prepared drug is a white crystalline . substance. having an intensely bitter taste. It is extensively used in medicine as a tonic. Employed in New Zealand as a rabbit-poison. • Poisoning cases occur mostly in small animals, particularly dogs, but strychnine is also a source of danger to sheep and the larger animals. It acts on the central nervous system, and produces convulsive seizures followed by a period of relaxation. The symptoms are similar to those of lockjaw. Two or three grains would be sufficient to poison a sheep, and slightly less than half a grain to poison a dog. . .. In the case of a dog an emetic should be given. The best physiological antidote is choral hydrate. Others are tobacco and permanganate of potash. Needless to say, any attempt to antidotal treatment must be carried out rapidly. Ragwort. — This poisoning is due to stock eating the common species of ragwort [Senecio Jacobaeai) found in this country. It is the cause of so-called Winton disease in New Zealand, Pictou disease in Canada, and Molteno disease in South Africa. It is worthy of note that the major portion of the original investigation work into the poisonous effects of ragwort was carried out in New Zealand by Dr. J. A. Gilruth. As is well .-known, many areas of this country are badly overrun with the weed, and losses of stock due to its cause are by no means uncommon in those districts.

Ragwort poisoning has occurred in horses, cattle, and sheep, and roughly that is also the order of susceptibility. The plant contains

one or more poisonous alkaloids, whose chief function is to produce a slow chronic reaction in the liver, rendering that organ what is technically known as cirrhotic. Actually, instead of being friable the liver becomes paler than normal in colour, and hard. This is due to the destruction of true liver-cells and their replacement by coarse white fibrous tissue condition similar to that occurring in man in chronic alcoholic poisoning.

Having regard to the chronic nature of the condition, it will be easily realized that the process of liver-destruction has reached a fairly advanced stage before symptoms are shown by the animal. That the toxic principles are operative long after the ragwort has ceased to be a portion of the diet is frequently evident in many ■cases noted, often where an interval of three or four months must have elapsed before the .first appearance of symptoms. Curative treatment is therefore practically out of the question. Symptoms appear gradually : affected animals become dull and lose condition ; later the gait becomes staggery, , and there is often a tendency to fall into obstaclesa period of intoxication. They gradually drift into a hopeless condition of semi-consciousness, eventually falling down and becoming unable to rise, and so death takes place.

Sheep appear to be more resistant than horses and cattle, but they also cannot be permitted to ingest ragwort indefinitely. They are often used successfully for keeping down the growth, and for this purpose it is most suitable to stock them heavily on ragwortinfested pasture in the spring. If sheep have been on ragwort too long without a change deaths may take place quite suddenly ; these are notably increased if such sheep are .driven distances. A condition of jaundice is often noticed during life, though not always, but there is considerable tendency for the carcass to assume a yellow appearance after death. This is due- to the absorption of bile, and has nothing whatever to do with the fact that ragwort has a yellow flower, as is sometimes popularly supposed.

In consequence of the general hopelessness of individual treatment, work should be concentrated on means of effective control if not complete eradication of the ragwort. This must be an accomplished fact before poisoning from this cause will cease altogether. . Tutu. — This shrub (Coriaria ruscijolia) is commonly' seen in the bush and on hillsides and banks in many parts of this country. As a rule stock do not eat tutu unless there is a shortage of natural feed. Poisoning is often noted after stock have been driven and then eaten the shrub on empty stomachs. The symptoms are those of excitement, with unsteady gait and nervous twitchings, and the animal is frequently blown. If discovered alive treatment is possible by relieving the blown condition by puncturing. Suitable medicinal treatment is the administration of i oz. of carbonate ■of ammonia dissolved in thin oatmeal gruel.

General.

There are a few other causes of poisoning of less importance, but space will ■ not permit a detailed description of them here. Many of the types of symptoms are common to more than one

kind of poison, and it is sometimes difficult to diagnose a case specifically as being due to poisoning or not. But careful consideration of the points touched on should be a helpful means of avoiding errors and provide stimulation to greater powers of observation.

Note. —For detailed information regarding the indigenous plant poisons, a series of articles in the Journal entitled " The Poisonous and Suspected Plants of New Zealand,” by B. C. Aston, may be referred to. The articles appeared in Volumes 16 (p. 324), 17 (p. 6), and 26 (pp. 78, 149, 230). —Ed.