NITRITE POISONING IN CATTLE AND PIGS

Putaruru Press, Volume XXI, Issue 1239, 17 July 1947, Page 2

NITRITE POISONING IN CATTLE AND PIGS

SYMPTOMS DESCRIBED Thistle Infected. Pastures During the past 12 years sudden deaths of cattle and pigs after eating raw mangolds have been reported occasionally, writes A. D. M. G. Laing, veterinarian, Hastings, and I. G. Mclntosh, toxicologist, Animal Research Station, Wallaceville; in ths New Zealand Journal of Agriculture. If any symptoms have /been noted at all, they have been staggering, rapid breathing, and sometimes convulsions, with collapse and death within an hour. Usually, however, the animals have /been found dead by the owner, death having occurred- so suddenly that -no symptoms have been observed. 'This- type of poisoning, associated with the use of mangolds, has not bean frequent, but d-uring the autumn cf .1946, when the drought broke, and in -the winter and early spring, a substantial number of cattle was lost in Hawke’s Bay. When symptoms were observed- they Were as described together with occasional bloating, abdominal pain, and diarrhoea. Abortion occurred in some of the animals which recovered. The only abnormalities noted in post-mortem examination were an engorgement of the surface blood vessels, visible whan the carcases were skinned, and- an unusually-dark red or even chocolate-brown colour of the blood. Danger of Thistles In a number of these cases no man-golds had been fed- out, but the animals, usually hungry run cattle, had been turned on to land where either winged- thistle (Carduus tenuiflorus) or variegated thistle (Silylbum Mari.anum) had grown so vigorously that the pasture was seriously reduced and thistles were the only feed- available. This article emphasises the dan gars of allowing, a further spread of thistles through the country and- indicates measures to prevent loss of stock turned on to thistle-infested pastures- or given a supplementary diet of mangolds-. No similar trouble -with either sheep or horses has been reported. The disease is not restricted to New Zealand, very heavy losses having occurred in New South Wales when hungry cattle were allowed to -gorge themselves- withthistles. In America heavy losses have followed the feedin/g out of oat hay. To date only one such case of oat-hay poisoning has /been reported in this country. Usually mangolds and oat hay can be fed out and thistles can be grazed with safety, hut occasionally circumstances arise which may lead to poisoning and l loss of stock. Nitrate Content’ Trouble occurs when the plant has- developed a high concentration of potassium nitrate, a salt which is present in varying amounts in all -plants, the amount being governed'by the species of plant, the fertility of the soil, the stage of growth, and

the climate. ’Generally, high fertility, rain after a drought, and young growth favour a high nitrate content. The salt is very -like sodium nitrate (the Chile saltpetre of commerce) in its chctmical properties and is used medicinally. Normally its toxicity is low, and in the animal most of it is changed into, harmless products- or excreted- unchanged in theurine; an insignificant a-mount is usually converted to poisonous -material. Where it occurs in plants it is usually accompanied iby a corresponding amount of a sub-stance called an , enzyme*, which can convert the relativelyh armless nitrate into a poisonous material known at nitrite. Furthermore, certain soil bacteria and some which are normal inhabitants of the digestive system of an animal also hava to a limited extent the power of converting nitrate into nitrite. Hence, when an animal eats a large a-mount of a plant with a high nitrate content together with sufficient associated einzyme, conditions are favourable for the formation of large and- possibly dangerous amounts of the poisonous nitrite.

Effects of Poison a The effects of the nitrate are palpitation—dilation of the -blood vessels- throughout -the body, necessitating an in-crease in the; rate of heart -beats; and an action on the red blood corpuscles which prevents -them from carrying out their function of absorbing oxygen in the lungs and carrying it fer us: throughout the -body. When that action has reached a certain point the animal dies from lack of oxygen —suffocation; if that point is not reached, the animal recovers in a few hours. However, in a pregnant animal -the foetus is likely to be killed, with consequent abortion of a dead calf in two to three days. Fortunately no chronic poisoning occurs, and an animal can receive a nearly-poisonous amount daily without suffering any harmful effects. Should the margin be exceeded at any time the animal will react in the same way as one receiving a single poisonous dose. There is- no method* by which a farmer can tell whether any of the foods mentioned are dangerous, and even in thei laboratory toxicity can foe cnlyv partially appraised.

Precautions Against Poisoning Symptoms of poisoning after the consumption of thistles or mangolds have usually been connected- with hungry stock having free access to such, food, or with stock unaccustomed to them being allowed overlarge quantities. Therefore poisoning should usually be preventable by taking care that such foodstuffs are not fed out too freely to hungry stock. Cattle should be allowed access to good mature grazing, or meadow or lucerne hay, before going on to mangolds. The same applies to country where thistles are the predominant grazing. If th® measures advisod are not possible because of a shortage of supplementary feeds, the* farmer must resign himself to a policy of severely curtailing the intake of now feed, mangolds or thistles, gradually increasing it over a .period of five to seven days. In that way

the risks of stock gorging them** selves, with consequent danger op " nitrate poisoning, seem to be gr«at« ly lessened, though not nacessarilj eliminated. ,* When -groups of cattle or pigs are being fed on mangolds for the first time and a number refuse te eat, as is 2iot infrequent, the .remainder will have mere than their allowance, possibly with disastrous results. The “pitting” of mangolds does not seem to prevent them from* causing nitrite poisoning. Treatment of Affected Stock f If symptoms of poisoning are observed, both healthy and affected stock should- immediately be takenoff the feed causing tha trouble.. Mature grass, if available, or plenty of good meadow or lucerne hay should- be fed as required. If possible a veterinary surgeon should be called in at once/ If called in time, ha can give injections which wiljl ■save fairly-advanced- cases. If runcattle are affected, however, cattle yards must be at hand to allow of' handling them.