Leeches are close relatives of the earthworm, though most species of leech are considered parasites as they feed on blood. Leeches are found all over the world, mostly in freshwater environments, though some species are found in marine ecosystems or on land, usually in damp areas. A full grown leech can be anywhere between 1 cm and 30 cm long, depending on species. Best known for their historical use in medicine to draw blood from patients, leeches attach themselves to their host and inject an anticoagulant which prevents the blood from clotting in order to feed. When attached to a host animal’s body, leeches will usually drop off on their own when they are sated, causing little harm to the host. When present in large numbers, however, they can leave the host weakened or cause them to die.
Effective parasite management is all about planning ahead, as management strategies take time to prepare and to show results. With summer nearly here, it’s time for readers in southern Australia to start thinking about “summer drenches” and developing low-risk worm paddocks for your weaners over winter.
It’s no secret that drenching too frequently can be costly, time-consuming and contribute to the development of drench resistance on your property. Grazing management is an effective, non-chemical way to limit the numbers of worm larvae to which your most vulnerable sheep are exposed, by allowing time for worms to die on pasture, breaking the lifecycle.
For those in winter and non-seasonal rainfall areas, smart grazing through summer can reduce worm populations on pasture leading into winter, by making the pasture less suitable for worm larvae and ensure that few worm eggs are deposited in the first place.
For weaners, who are most susceptible to worms in their first winter, this can make a big difference to their worm burdens, allowing you to reduce your reliance on drenching and improving weaners’ growth.
Flystrike is a high priority on the sheep management agenda at the moment, as large parts of Australia are predicted to see a wetter than average summer. Many contributors in our October State Outlooks noted an increase in fly activity through spring and into summer; to borrow from our Tasmanian contributor, Paul Nilon, “warmth and moisture, nothing else is needed”.
Flystrike management is a long-term commitment, as many strategies — such as adjusting the timing of your shearing and crutching, undertaking breech modification or breeding for resistance — require careful planning and ongoing work. If you haven’t already, consider developing a flystrike management plan, or reviewing your existing plan. FlyBoss provides tools to assist you with planning and prevention.
On properties where preventative treatments are not required in the majority of years, a threshold method, where treatment occurs once a set amount of strike is occurring, can be used to decide when to treat. For those looking at a season of high flystrike risk, or who are already dealing with struck sheep, chemical treatments can also be used carefully and strategically in conjunction with other management tools such as those listed above to further reduce the risk of flystrike.
Much like your children coming home with head lice, a new infestation of lice in your sheep flock is most likely to come from contact with lousy sheep. Sheep lice can cost you a small fortune — both in lost value of wool and in the time and money spent applying chemical treatments.
It goes without saying that spending a little time and money now to prevent the introduction of lice will save you plenty in the long run. Good biosecurity is an investment in a healthy and parasite-free flock, and it starts with checking in on your fences.
With lice, it’s safest to assume any sheep not under your management is infested and act accordingly. Maintaining or upgrading fences to be sheep-proof gives you peace of mind that outside sheep aren’t able to mix with your existing flock, and that your sheep aren’t able to get out and become lousy.
Have you found yourself drenching your goat herd too frequently? Did you know that you can breed goats for worm resistance, reducing the worm burden on your herd and ultimately requiring fewer drenches each year?
Goats that are resistant to worms limit the ability of the worm to grow, develop and produce eggs. This results in lower worm burdens overall and fewer eggs deposited onto pasture, slowing down the rate of infection or reinfection. You can breed for resistance by buying bucks from a stud which provides estimated breeding values (EBVs) for worm egg counts (WEC), and selecting a buck that balances lower than average WECs with other positive traits you’re trying to breed for.
Breeding goats that are more resistant to worms can reduce your reliance on drenching and provide you with another option for management of worms in your herd.
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Animal Health Australia