- DISEASE AND MANAGEMENT PROBLEMS
strike in sheep is a major problem in Australia. It can cause
serious loss in sheep numbers and in some districts is the worst
single problem. There are two types: primary and secondary strikes.
Blowflies will not lay their eggs in dry situations therefore, 85% of
all trikes occur around the tail in the breech region. Sometimes
rain causes strike on the shoulder and along the back. Sheep bred
from plain bodied rams for sheep with plain non wrinkled bodies are
less liable to fly strike. To reduce strike tails should be docked,
crutching and mulesing carried out once a year. Jetting with a liquid
insecticide is a further control but it will only protect the sheep
for several weeks.
tick and similar parasites live on the skin of the sheep. They bite
causing intense itching and can destroy the fleece. Sheep with open
‘woolly fleeces are more liable to attack than merinos. Most keds
are removed during shearing and sheep should be dipped about 6 weeks
after shearing. By law all affected sheep must be dipped.
worst seeds affecting the wool clip are spear grasses, noogoora burr,
barley grass, burr trefoil and the corkscrew grasses. They have
spines or hooks which cling to the wool and thus reducing its value.
Seeds also get into the eyes of sheep, causing irritation and loss of
condition. Some seeds even penetrate the skin and enter the body.
With good pasture management stockowners can lessen the problem. For
example, lambing can be timed to avoid the period when seeds are
known to be a problem.
is the removal of wool from around the eyes. This prevents wool
blindness and helps to prevent seeds entering the eyes.
wool enters the mill it is “scoured” to remove dirt, sweat and
grease, and then “carded”. It is during this process that the
wool fibres are drawn apart. The first setp is to produce “top”.
If a contaminant such as a bale fastener or a hook get caught up, the
result can be thousands of dollars worth of damage to machinery.
While metal and plastic can cause problems in scouring, more serious
and expensive problems occur when the contaminated wool leaves this
stage of production.
include cigarette butts, clothing and hessian bags that have the same
fibrous properties as wool. In the carding machine these canbe broken
up and separated into strands which then pass into the semi processed
stage known as “top”. However, the worst contaminant is
polypropylene (hay bale twine, super phosphate bags and feedbags) as
it breaks down into small fibres like wool. The mills imploy a team
of people to handpick each strand of “poly”, an expensive
is caused by certain bacteria which are transferred onto the ground
from the feet of affected sheep. Healthy sheep pick up the bacteria
which will cause decay of the soft tissues inside the hoof. Footrot
spreads rapidly in wet weather and it is expensive to control. The
hooves of affected sheep must be pared away and dressings applied.
The spread of footrot may be halted by walking sheep through a foot
bath of copper sulphate solution but will require a number of
treatments before the disease is brought under control. Romney marsh
sheep are almost immune to this disease as they originated in wet and
boggy marshlands of England.
liver fluke of sheep spends part of its life inside the bodies of
fresh water snails. It then becomes attached to vegetation alongside
the stream so that grazing sheep will swallow the fluke. It then
travels from the intestine up the bile duct to the liver. As the
fluke grows the sheep loses condition and may die. Fluky sheep may be
treated by drenching but it is essential to kill all snails in the
streams and swamps. This is done by spreading copper sulphate in the
main worm infestation suffered by sheep is the barbers pole or
stomach worm. The worm causes loss of blood which weakens the sheep
causing anaemia. It is more of a problem after spring and summer
rains. Worms are controlled by drenching. Another worm is the black
scour worm. This worm causes a of loss condition. It is controlled
with a drench of phenothiazine. Nodule worm also causes a loss
condition and the sheep will develop a humped back condition. Sheep
will never fully recover and it is necessary to drench a number of
toxaemia or twin lamb disease occurs in ewes just before they are
due to lamb. It often occurs with ewes which were in prime condition
but suffer a feed shortage later on. It is more likely in ewes
sheep are on lush pasture bacteria may multiply rapidly producing a
poison which kills the sheep. This is called entero toxaemia
and is controlled with a series of injections of a vaccine.
drought periods sheep will require hand feeding. Weight changes in
the sheep can be estimated by regular inspections but weighing is
better. When sheep begin to lose more than 450 grams per week it
becomes critical. Sheep can lose up to 25% of body weight.
farming is much more labour intensive than cattle raising. Pastoralists
in the Western Division work in a high risk situation
and may only muster sheep 3 times a year. In the marginal areas
sheep may only be crutched, shorn, dipped, ewes mated and lambs
marked. Sheep running in the hottest parts of Australia are usually
shorn in summer before the fly strike becomes worst.