Managing the shedding of eggs from ewes in spring can be one way of minimising the worm larvae uptake by lambs later in the grazing season and thus reduce the need for subsequent treatments.
The rationale behind treating ewes is that it reduces the number of worm eggs a ewe puts onto pasture when her immune system relaxes around lambing – a term known as the spring rise.
The risk period is from around 2 weeks before lambing until around 6 weeks post lambing. The period of increased egg shedding leads to pasture contamination and is a risk to lambs.
Targeting Ewes to Treat
Challenged ‘at risk’ ewes tend to be the ones that produce the most eggs - this can be ewes that are under nutritional stress e.g. in lower body condition, younger ewes and triplet-bearing ewes.
Along with larvae that have overwintered, this will be the source of the worms that will challenge lambs later in the season. If you can differentiate between the ewes that put out the most eggs from those that shed the least, treatment can be selective.
It is vital when worming ewes at lambing that you target your treatment to these most ‘at risk’ ewes leaving at least 10%, but preferably more, of the ewes untreated. It is also important to note that these ewes need to be spread between different grazing mobs. This is to help reduce the risk of anthelmintic resistance.
Product Choice
The only product that is proven to suppress the spring rise is long-acting moxidectin i.e. CYDECTIN® 2% Long Acting injection for sheep. This can help reduce the risk of pasture contamination and in conjunction with FEC monitoring can reduce the number of treatments required for lambs, saving time and money.
However, when opting to use a persistent product, it must be used with care. We have been working with the Sustainable Control of Parasites in Sheep (SCOPs) and have agreed the priority must be to preserve moxidectin both as an anthelmintic for worms and treatment for sheep scab. This means it must not be used year on year in flocks or more than once within the same season.
For example, if you have used the product in the ewes at lambing, you should think about using an alternative product to control scab, something you should discuss with your animal health care provider. You can read more on the recommended dos and don’ts Here.
Using a long-acting product can form a useful part of a flock parasite programme in order to minimise the use of other anthelmintic treatments in that breeding year, and by reducing pasture contamination for those sheep that will graze the pasture in the next year.
However, it is vital all worm treatments should be discussed with your animal health care provider who will be able to advise and support you with the most appropriate worming strategy for your farm.
