If the bush telegraph is correct, it seems there are a fair few pre-lamb drench capsules going back out onto farms in some parts of the country this winter. Wormwise programme Manager and vet Ginny Dodunski outlines some management factors to consider before using capsules this winter.
Most capsule re-sellers are hopefully advising farmers to use these in a limited way. For both sustainability and cost benefit reasons, it makes sense to limit their use to the ewes that are most likely to come under pressure from worms over lambing.
While parasites are rarely the primary cause of low condition and low ewe performance, underfed light ewes will certainly suffer more under a parasite challenge. Ewes carrying multiples have higher energy demands and are more vulnerable than singles.
If we accept that light multiple ewes require priority treatment, we need to think about two things:
- How to best manage and feed them
- If they’re given a long-acting pre-lamb product, what to do with the areas they’ve been grazing to avoid amplifying resistant worms that may be accumulating in their paddocks.
Simply treating light ewes with a capsule and throwing them back into the main ewe mob is an easy way to dilute out the resistant worms (provide refugia), but this is probably expecting a bit much of the product. These ewes have become light for a reason, and if left to compete in a big mob, are unlikely to do well.
The most vulnerable sheep are best managed together in the safest paddocks at lambing. So, if we have whole paddocks of capsule treated ewes, we need to set some rules about what grazes those paddocks later.
Feeding and management
All multiple ewes need to be fed well in the weeks leading up to lambing. Light multiples would ideally be in their own, smaller mob, to reduce competition. It can be logistically difficult to have lots of mobs at this time of the year, so mixing and matching can be one solution, for example, running light MA twins and two-tooth twins together as a smaller mob.
Light multiple ewes don’t have the body reserves to ‘milk off their backs’, so they need to be set stocked in a situation where pasture covers and/or pasture growth rates can easily meet their energy demands. Light stocking rates can facilitate this. Pasture quality issues after docking/tailing can be addressed with cattle or by getting a rotation going.
Nitrogen (N) may still be an option to lift feed during lactation. A recently published Agresearch study at Woodlands applied 40kgN/ha to treated paddocks after lambing – they got a 28:1 pasture response and an extra 2.3kg/head of lamb weaning weight. This emphasises the impact of having easily harvestable green feed for lambs in the second half of lactation. Ewes were 3.8kg heavier; a real advantage for flexible summer management. Average cover on the N treated areas was just over 1800kgDM/ha – not exactly a quality blow-out!
There really is no substitute for good feeding.
Dealing with ‘resistance hotspots’
On most farms, ewes treated with a long-acting pre-lamb product will continue to harbour some worms.
It’s good practice to monitor with faecal egg counts after treatment to understand how many worms are surviving and contaminating lambing areas. The loss of immunity in light, underfed ewes will see more of the eggs they shed hatch and develop into infective larvae, than would happen in a well-fed ewe in good condition.
Docking/tailing is a convenient time to sample these sheep. Depending on the results, you can then have a discussion with your animal health advisor about whether or not to use an exit drench. It’s vital that the product you choose for this job is highly effective. On most farms this is no longer a triple combination.
Finally, you need to make a plan for what happens to your ‘capsule’ paddocks after lambing. Having small numbers of untreated ewes in amongst treated ones right from the get-go is a smart move, but it will still be wise to treat these paddocks as ‘red zones’ and look for ways to clean them up. Ideas include dropping them out of sheep rounds for a while and grazing with cattle, shutting up for hay or deferred grazing. At the very least, try to avoid weaning lambs back into these paddocks. Grazing these paddocks with undrenched ewes over summer will help deposit small numbers of ‘good’ worms back into the mix.