A closed flock policy offers the advantage of knowing the background breeding of replacements entering the flock. However, with the breakdown of the national flock including greater than 50% of flocks with less than 50 ewes, for many, a breeding policy of producing terminally-bred lambs for slaughter and purchasing replacements is a more straightforward approach.
This poses challenges in sourcing sheep with good maternal credentials and reducing the risk of disease entering the flock, but, on the other hand, it also provides opportunities for producers in progressing down a specialised system of marketing replacements with a proven track record and high health status.
Even with flocks operating a closed flock policy, there are very few farms that have a 100% closed flock, with a ram purchased from time to time.
Therefore, having a good quarantine protocol in place is a critical component. This will differ between farms, but there are a number of variables that should be constant across each.
Purchase in adequate time
When it comes to the length of the quarantine period, the longer the better. As a general rule of thumb, animals should be quarantined for a minimum of 21 days before joining the rest of the flock.
For ram lambs in particular, it is advisable to purchase well in advance of the breeding season, especially if rams have to change from a cereal-based diet to grass only or grass diet with low levels of concentrate supplementation until mating.
Safeguard against resistant worms
Anthelmintic resistance is becoming a growing problem for sheep flocks, with resistance rising to varying degrees to benzimidazole, levamisole and avermectin, all active ingredients in commonly used products.
To combat this risk, there are two approaches recommended. The more traditional approach used in recent years is to treat animals with a product containing levamisole (yellow drench) and avermectin, with a moxidectin-based product the drug of choice due to lower levels of resistance.
A more modern approach that is now regarded as the safest approach is to treat animals with a moxidectin product and one of the new-generation wormers – Zolvix, which contains the active ingredient monepantel, or Startect, which contains the new active ingredient derquantel and abamectin.
Sheep should be treated on arrival and kept off pasture for 24 to 48 hours, so that worm eggs present in the gut will not pass on to pasture.
Following treatment, sheep should be turned on to pasture that is referred to as dirty; that is, ground that has been previously grazed by sheep.
Investigate presence of liver fluke
Getting as much background information as possible from the owner of the sheep will help in strengthening the quarantine protocol.
Where previous liver fluke treatments are unknown, animals should be treated as potentially having liver fluke and treated accordingly. The advice is to use a product containing trichlabendazole and another product with an active ingredient such as closantel to safeguard against resistance to trichlabendazole.
External parasites
Dipping is the optimum method in controlling external parasite risks such as sheep scab, lice, ticks, etc. For complete control, sheep should be immersed for 60 seconds, with their head plunged under the solution two to three times.
If dipping is not an option, an alternative is to treat sheep scab with the use of an avermectin product. However, be wary as there are no injectable products that cover all external parasites.
In this scenario, treatment will need to be doubled up with suitable pour-ons that cover sucking and biting lice and other target external parasites.
It is also important to read manufacturers’ product guidelines closely, as some products need repeat treatment seven to 14 days later to target parasites that have hatched from eggs.
Early intervention critical with lameness
Sheep should also be footbathed on arrival. The commonly used products are copper and zinc sulphate (10% solution) and formalin (3%), although other products are available on the market. Sheep should be monitored closely throughout the quarantine period and run through the footbath at any stage of handling.
Particular caution should be paid to footrot or CODD (contagious ovine digital dermatitis) which can spread rapidly through a flock.
What should be considered in
vaccination?
While vaccinations often contribute to the greatest cost of a quarantine health programme, they have an important role in reducing the risk of disease.
Their use can be reduced in some cases by purchasing from known high-health status flocks. The three main ones to consider are clostridial disease, enzootic abortion and toxoplasmosis.
The clostridial disease vaccine should be administered shortly after arrival, with a booster administered four to six weeks later to build full immunity.
Decisions will need to be taken on selecting a vaccine that covers the full range of clostridial diseases or one that also provides protection for pasteurella pneumonia.
Enzootic abortion or chylamdia abortus is a highly contagious disease of sheep that hits in late pregnancy.
The only vaccine available is Enzovax, which is administered at least four weeks before the start of the breeding season. It can be administered at the same time as Toxovax, which prevents toxoplasmosis, and must be administered at least three weeks before the start of the breeding season.
Purchased-in sheep can be especially at risk to toxoplasmosis, as they may not yet have developed an immunity resulting in high levels of barrenness, abortion and the birth of weak lambs.
Read the full focus section on sheep breeding here
A closed flock policy offers the advantage of knowing the background breeding of replacements entering the flock. However, with the breakdown of the national flock including greater than 50% of flocks with less than 50 ewes, for many, a breeding policy of producing terminally-bred lambs for slaughter and purchasing replacements is a more straightforward approach.
This poses challenges in sourcing sheep with good maternal credentials and reducing the risk of disease entering the flock, but, on the other hand, it also provides opportunities for producers in progressing down a specialised system of marketing replacements with a proven track record and high health status.
Even with flocks operating a closed flock policy, there are very few farms that have a 100% closed flock, with a ram purchased from time to time.
Therefore, having a good quarantine protocol in place is a critical component. This will differ between farms, but there are a number of variables that should be constant across each.
Purchase in adequate time
When it comes to the length of the quarantine period, the longer the better. As a general rule of thumb, animals should be quarantined for a minimum of 21 days before joining the rest of the flock.
For ram lambs in particular, it is advisable to purchase well in advance of the breeding season, especially if rams have to change from a cereal-based diet to grass only or grass diet with low levels of concentrate supplementation until mating.
Safeguard against resistant worms
Anthelmintic resistance is becoming a growing problem for sheep flocks, with resistance rising to varying degrees to benzimidazole, levamisole and avermectin, all active ingredients in commonly used products.
To combat this risk, there are two approaches recommended. The more traditional approach used in recent years is to treat animals with a product containing levamisole (yellow drench) and avermectin, with a moxidectin-based product the drug of choice due to lower levels of resistance.
A more modern approach that is now regarded as the safest approach is to treat animals with a moxidectin product and one of the new-generation wormers – Zolvix, which contains the active ingredient monepantel, or Startect, which contains the new active ingredient derquantel and abamectin.
Sheep should be treated on arrival and kept off pasture for 24 to 48 hours, so that worm eggs present in the gut will not pass on to pasture.
Following treatment, sheep should be turned on to pasture that is referred to as dirty; that is, ground that has been previously grazed by sheep.
Investigate presence of liver fluke
Getting as much background information as possible from the owner of the sheep will help in strengthening the quarantine protocol.
Where previous liver fluke treatments are unknown, animals should be treated as potentially having liver fluke and treated accordingly. The advice is to use a product containing trichlabendazole and another product with an active ingredient such as closantel to safeguard against resistance to trichlabendazole.
External parasites
Dipping is the optimum method in controlling external parasite risks such as sheep scab, lice, ticks, etc. For complete control, sheep should be immersed for 60 seconds, with their head plunged under the solution two to three times.
If dipping is not an option, an alternative is to treat sheep scab with the use of an avermectin product. However, be wary as there are no injectable products that cover all external parasites.
In this scenario, treatment will need to be doubled up with suitable pour-ons that cover sucking and biting lice and other target external parasites.
It is also important to read manufacturers’ product guidelines closely, as some products need repeat treatment seven to 14 days later to target parasites that have hatched from eggs.
Early intervention critical with lameness
Sheep should also be footbathed on arrival. The commonly used products are copper and zinc sulphate (10% solution) and formalin (3%), although other products are available on the market. Sheep should be monitored closely throughout the quarantine period and run through the footbath at any stage of handling.
Particular caution should be paid to footrot or CODD (contagious ovine digital dermatitis) which can spread rapidly through a flock.
What should be considered in
vaccination?
While vaccinations often contribute to the greatest cost of a quarantine health programme, they have an important role in reducing the risk of disease.
Their use can be reduced in some cases by purchasing from known high-health status flocks. The three main ones to consider are clostridial disease, enzootic abortion and toxoplasmosis.
The clostridial disease vaccine should be administered shortly after arrival, with a booster administered four to six weeks later to build full immunity.
Decisions will need to be taken on selecting a vaccine that covers the full range of clostridial diseases or one that also provides protection for pasteurella pneumonia.
Enzootic abortion or chylamdia abortus is a highly contagious disease of sheep that hits in late pregnancy.
The only vaccine available is Enzovax, which is administered at least four weeks before the start of the breeding season. It can be administered at the same time as Toxovax, which prevents toxoplasmosis, and must be administered at least three weeks before the start of the breeding season.
Purchased-in sheep can be especially at risk to toxoplasmosis, as they may not yet have developed an immunity resulting in high levels of barrenness, abortion and the birth of weak lambs.
Read the full focus section on sheep breeding here
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