Practical biosecurity for sheep producers

By far the greatest risk for disease introduction on farm is the purchase of livestock. Buying sheep especially brings risks of introducing a number of conditions that can cause ongoing production losses and incur significant eradication costs.

A good biosecurity strategy will go a long way towards minimising the disease risk from purchased sheep. It doesn't have to be expensive or elaborate, and is best thought of in three components:

• pre-farmgate
• farmgate
• post-farmgate.

Pre-farmgate biosecurity

Pre-farmgate biosecurity is all about the background and physical checks you do before you decide to buy. The Sheep Health Statement (SHS) contains most of the history you need for an initial risk assessment, so ask for it from the vendor, read it and understand it. If the sheep don't come with an SHS, don't buy them.

Try to buy from reputable vendors, and limit the number of lots you buy, because the more sources you buy from, the greater the risk. If you bought from the same vendor last year and were happy with the sheep, buy from the same producer again  —  better still, buy direct.

Get in the pen and check the sheep for footrot and lice. Pick out 20 sheep, targeting any that look proppy or have pulled wool, then perform 20 fleece partings per sheep to look for lice. Check the feet of the lame ones  —  if you find any evidence of footrot, don't buy them.

When buying rams, make sure they come from brucellosis-free accredited flocks. Never buy rams from the saleyards, and still do your own checks as a matter of habit.

Farmgate biosecurity

When you get the newly purchased sheep home, you need to do a few things as they come off the truck. A footbath in zinc sulphate should remove any footrot bacteria acquired in the saleyards or on the truck. However, if the sheep already have footrot, this footbath is unlikely to eradicate it.

The sheep will also need a quarantine drench to remove multiple-resistant worms. This must contain a mixture of four different active ingredients, including one of the new drenches:

• Zolvix® (monepantel) and a triple drench—abamectin or moxidectin with levamisole (clear) and benzimadazole (white)
• Startect® (derquantel and abamectin) and a combination drench—levamisole (clear) and benzimadazole (white).

If the sheep come from fluke country, a flukicide should also be given. After the drench, keep the sheep in the yards for 48 to 72 hours to allow them to empty out any worm eggs  —  then check their parasite burden with a faecal egg count 10 to 14 days later to make sure the drench has worked.

You can treat new sheep for lice by dipping them, but only if the sheep are less than 4 to 6 weeks off shears. If they have more than 6 weeks wool or if you want to use a backliner, you'll have to shear them first, which might be difficult to justify economically when the sheep are in short wool.

Post-farmgate (on-farm)

Even when you have done all your checks and induction treatments, new sheep still pose a disease risk, so you must keep them isolated from other sheep until you are sure they don't have footrot or lice. For footrot, you need to keep them isolated until after a good spread period of warm, wet weather, which is usually at the end of normal spring in Victoria. To be sure the sheep don't have lice, keep them separate for at least 6 months or until after the next shearing. (Sheep need 6 months of wool on them to enable detection of lice, but more certainty is provided if you wait until the next shearing.)

Sheep in quarantine can be moved through yards and can be drenched. The golden rule is that other sheep can't cross their path for 7 days. So if you have to yard the sheep in quarantine, do them last, followed by spelling the laneways and yards for 7 days. If you need to move them, other sheep can safely enter the old quarantine paddock after 7 days.

Rams joined to a recently purchased, quarantined flock are then also under quarantine—they should be kept separate from your other flock rams until the quarantine period is over, and they are confirmed free from lice and footrot. Alternatively, consider using the cull rams to mate with your recently purchased ewes.

At the end of the quarantine period, conduct another inspection to ensure that the sheep are free from the condition in question by parting the fleece of 20 sheep and examining the feet of any lame sheep.

The beauty of on-farm quarantine is that, if you have inadvertently brought footrot or lice onto the farm, you will limit the condition to a small proportion of your flock  —  as a result, it will be much cheaper and easier to deal with. Minimising the disease risk with introduced sheep requires a little effort and some planning, but costs very little and provides immediate, ongoing and cumulative returns.

Biosecurity checklist when purchasing sheep (lambs, ewes, wethers or rams)

Pre-farmgate

• examine Sheep Health Statement
• undertake background checks
• examine sheep for footrot and lice, and rams for brucellosis.

Farmgate treatments

• quarantine drench (4-way drench)
• footbath (10% zinc sulphate)

Post-farmgate quarantine paddock

• undertake worm egg count after 10 to 14 days
• quarantine for footrot until the end of spring
• quarantine for lice for at least 6 months or until the next shearing.

Dr Pat Kluver, Livestock Biosecurity Network, Melbourne