Breeding sales of ewes and rams have kicked off, with a busy calendar of sales taking place over the next six to eight weeks. It is not the purchase of breeding sheep that presents a risk of introducing disease onto a farm, any animal coming onto the farm from an outside source presents a risk. Even where farms are operating a closed flock policy, there are very few operating a 100% closed flock policy, with rams purchased occasionally.
Therefore, having a good quarantine protocol in place is a critical component of your farm’s flock health programme. 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 and preferably 28 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 an intensive, cereal-based diet to a grass-only diet or a grass diet with low levels of concentrate supplementation until mating.
Purchased sheep should be quarantined on arrival to the farm and remain in quarantine until you are happy there are no risks of introducing disease to the rest of the flock.
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 a new-generation wormer. There have been two new additions to this list in recent years – Zolvix, which contains the active ingredient monepantel, and Startect, which contains the new active ingredient derquantel and abamectin. Startect is experiencing supply issues, so it is likely that Zolvix will be the only option available. It is also worth noting that these products are prescription-only medicines, meaning they have to be provided by a veterinary practice.
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 out to pasture that is referred to as dirty; that is ground that has been previously grazed by sheep.
Anthelmintic resistance is becoming a growing concern and as such sheep should receive a double treatment on arrival to the farm.
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 dealt with 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.
Dipping is the optimum method for 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 and have not been covered by the initial treatment.
Administering a clostridial disease vaccine boils down to personal preference and the history of disease on the farm, but is a small cost to safeguarding your investment.
Early intervention critical with lameness
Introducing serous lameness-causing ailments, such as CODD (contagious ovine digital dermatitis), is becoming a rising concern – with the disease growing in frequency in recent years. All sheep should be examined for any signs of the disease or for any other ailments causing lameness.
Sheep should be footbathed as a precautionary measure and a treatment plan should be put in place for any lame sheep. 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.
Dipping sheep is the ultimate treatment for addressing all forms of external parasites at the one time.
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 animals to 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.
Where replacements are concerned 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.
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