sheep disease and management problems

SHEEP - DISEASE AND MANAGEMENT PROBLEMS

FLY STRIKE

Fly 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.

KED

Sheep 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.

SEEDS

The 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.

WIGGING

Wigging is the removal of wool from around the eyes. This prevents wool blindness and helps to prevent seeds entering the eyes.
OTHER CONTAMINANTS

When 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.

Offenders 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 process!

FOOTROT

Footrot 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.

FLUKE

The 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 water.

WORMS

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 times.

PREGNANCY TOXAEMIA
Pregnancy 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 carrying twins.

ENTERO TOXAEMIA

When 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 FEEDING

During 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.
LABOUR

Sheep 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.