Ragwort poisoning

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Ragwort
poisoning

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horses here


Introduction

There are a large number of poisonous plants to be found,
although their abundance will vary greatly from place to
place. Horses and ponies at pasture are often at risk,
especially when grass is in short supply. Perhaps one of
the more common plants and unfortunately one of the more
deadly is Ragwort. Ragwort (Senecio Jacobaea L.)
poisoning is the most common cause of liver damage in
horses. Ragwort is a hardy biennial. It flourishes in waste
ground and roadside verges from where it invades nearby
fields. The growing plant is not palatable to grazing
animals and is usually ignored by horses, except when the
grass is extremely poor. It thus has a competitive
advantage over the other plants (including grass) and
fields quickly become heavily contaminated.



Ragwort

How does
ragwort affect animals?


Ragwort contains pyrrolizidine alkaloids which are
poisonous to horses, other farm animals such as sheep and
cattle and also to wild animals such as hare and deer. It
is important for horse owners and horse pasture owners to
recognise and control this potentially fatal plant.
Unfortunately, some horse-keepers do not control ragwort
growth and spread as they do not expect their horses to eat
the plant and probably don’t appreciate the reality of the
suffering their animals could be caused. It is true that
ragwort does have a bitter taste which often deters horses
from eating it. However, if grass becomes sparse (e.g.
following a period of hot dry weather) horses may resort to
eating plants they wouldn’t normally eat, including ragwort
if it is present. Some horses develop a liking for the
bitter taste and may choose to eat it even when there is
sufficient palatable grass available to graze on. If eaten,
as little as 2lb of fresh ragwort can be sufficient to
cause fatal damage. Uncontrolled ragwort left growing in
and around horse pastures exposes horses and ponies to
poisoning and possibly death, and the infestation will
increase each year as plants set seed.

Equines and bovines are more susceptible to ragwort
posoning than other livestock. Young animals are more
susceptible than mature animals. Ragwort poisoning can
occur at any time of the year. The toxins in ragwort are
cumulative and result in irreversible liver damage and
digestive disorders. A small intake of ragwort over a long
period can be just as damaging as a large intake on a
single occasion. Ragwort remains toxic but becomes more
palatable when dried and is particularly dangerous in hay
and haylage. Little can be done dor an animal once the
clinical symptoms appear.

Clinical
symptoms


Loss of condition (weight loss, dull coat, depression),
poor appetite and constipation, pain from gut area,
swelling under the abdomen (oedema), photosensitation
(sunburn, which is restricted to the white areas) and
sometimes jaundice (yellow color to mouth and eye).

Terminal signs: nervous signs develop (yawning, head
pressing and ataxia), restlessness and aimless
uncoordinated movement. Animals may appear blind, pressing
heads against solid objects, abnormal gait and stance. Most
affected animals die after a period of illness varying from
a week to several months.

Diagnosis

The disease can be confirmed by your vet in two ways. A
blood test for specific liver enzymes (GGT and ALP) is the
most usual, in cases where doubt arises a liver biopsy can
be performed.

Treatment
Once actual symptoms have developed, especially
any neurological symptoms, the prognosis is poor, however
in the early stages careful dietary control and vitamin
supplementation can be helpful.

Sources of
Ragwort poisoning


• Livestock tend to avoid eating ragwort on good pastures.

• Where there is over-stocking and grass is scarce the weed
will thrive and is unavoidably eaten.

• The poisons in ragwort are not destroyed by drying. Dried
grass, hay and silage are common sources of ragwort
poisoning, it can be undetectable and consumed readily.

• Ragwort becomes much more palatable when cut or wilted,
as it loses its bitter taste.

How to
recognise ragwort


Seedlings can be found from autumn onwards – the first
leaves have a characteristic spade shaped blade, notched at
the apex (10-15mm length).

The first true leaf is hairless, 10-12mm in length and oval
shaped with a smooth edge. As the plant grows the leaves
produced show a gradual increase in the degree of lobbing
and waviness typical of the older ragwort plants. Leaves
also become hairier as the plant gets older.

Rosettes can be found from early spring onwards – circular
cluster of leaves, usually deep green on top and underneath
covered in a cottony down, the leaves have a ragged
appearance. The rootstock, basal leafstalks and lower parts
of the stem may have a purplish/ red colour. (If biennial
will over winter as a rosette and during the second year
send up a single leafy stem, which will produce numerous
flower heads.)

Mature plant reaches between 1-2m in height, the stems are
tough and often tinged purplish/red near the base, but
brighter green and branched above the middle. Flowering
occurs May to late October. The bright yellow flowers are
daisy-like. Most plants die after flowering, creating a gap
suitable for immediate colonization by seedlings.

The seeds have a downy appendage making them readily
dispersible by the prevailing wind, but can also be
dispersed via water or spread by people and livestock.

How do you
control ragwort in your pasture?


Control of ragwort is the only way to avoid ragwort
poisoning. Over and under grazing create open patches where
ragwort can readily establish itself.

Ragwort will not establish where there is a dense vigorous
sward. Such a pasture can be best achieved though
controlled grazing and/or regular fertiliser applications.
This encourages root development of grasses and makes a
valuable contribution to preventing re-infestation.

• It is important to remove all potential.

• To remove the danger to your animals a control strategy
must be employed.

• The chosen method of control should be the one least
damaging to the environment and human health, whilst still
being an effective method of control.

Short Term Methods/ Small
Ragwort Infestations


Digging/Pulling:

• Always wear gloves

• Needs to be done before flowering has completed

• Ragwort is more easily removed in the spring when the
plant is immature or after heavy rainfall when the ground
is soft

• Need to be carried out for at least 2 years as ragwort is
a biennial, or if the pasture has a history of ragwort
infestation this will have to be carried out annually due
to the remaining seeds in the soil

• It is important to remove as much of the root as
possible; ragwort can regenerate like docks from its root
fragments

Cutting

• At the early flowering stage reduces seed production

• Acceptable in an emergency situation, but generally is
not recommended since it encourages more vigorous growth

Never leave cut plants within reach of horses.

Long Term Methods/ Large
Ragwort Infestation


Weed-killers

Ragwort can be spot sprayed with a selective weedkiller.
This can be done all the year around but is best to spot
spray when ragwort is at the rosette state – in winter
months through to the end of July.



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