Traditionally ewes are given a drench pre-lambing, to help control the “periparturient rise”. This is when, around lambing time, a ewe’s natural immune defences are reduced and their normal capacity to remove worms from pasture is lost. We drench at this time to help maintain ewe condition in late pregnancy and early lactation and reduce the pasture challenge for young lambs.
Long acting drenches e.g. Exodus LA and capsules e.g. Bionic, have frequently been used for this, and are still indicated in some classes of stock. However as this is a time of year when there is generally low larval challenge, there are other options available that are more in keeping with modern Worm-wise principles.
Fluke treatment: If you routinely use a fluke drench e.g. Flukecare in the winter, this is a good opportunity to give this drench; the timing is usually good for a fluke drench and treating pre-lambing is appropriate and effective.
No Drenching: If MA ewes are in good condition (BCS>2.5) then they can be left undrenched pre-lambing, and given a drench e.g. Switch, at docking. At docking, drenching can be targeted to ewes that need it, and if they are still in good condition can be left undrenched. Some farmers, using this method, can move gradually to less and less drenching of MA ewes, and sometimes leave MA ewes undrenched year-round. Sufficient nutrition is vital if ewes are to be left without drenching. The immune response necessary to fight worm challenge requires ewes to have good body reserves.
Short acting drenches: e.g. Arrest, Switch, Matrix, are also frequently sufficient to give ewes a boost pre-lambing, and if some ewes, particularly singles are in good body condition, they can safely be left undrenched.
Targeted long acting drenching: Younger sheep i.e. hoggets and 2T, have fewer reserves, lower immunity and take longer to recover than MA ewes. It is generally these sheep that we would advise have a capsule or long acting drench, especially if they are carrying twins. It has been well documented that it is very cost effective to use these products in young sheep. As long as they are not used as ‘whole flock’ treatments their use is justifiable and safe.