March 2008 Update
Sustainable control of worms in sheep revolves around
· appropriate grazing management to minimise the risk of challenge
· appropriate choice of product used in the appropriate way
· appropriate timing of worming
· appropriate selection of stock to be dosed
Decisions on who to treat, with what and when must be reached after:
1. Considering the risk of challenge,
2. The grazing management (past, present and future)
3. The likely susceptibility to challenge of different ages of stock at different times of year.
It is impossible to provide a worming blue print that would be applicable to all farms, to all stock and to all circumstances. A few seasonal pointers to the decision making are as follows.
· A key time in the annual worm control program is the treatment of the ewe at lambing. The worming of the ewe as close to lambing and/or turnout is critical and in most cases non-negotiable.
· Where ewes and lambs are turned onto ‘safe’ pasture (not grazed by sheep in the previous 12 months) immediately after lambing then a conventional short acting wormer can be used.
· Where ewes and lambs are turned onto dirty pasture (grazed by sheep in previous 12 months) a long acting wormer drench (Moxidectin-Cydectin) must be used.
On dirty pasture there will always be more over-wintered worm larvae on the pasture than worms in the ewes. Ewes are highly susceptible to worm challenge at the time of lambing and for the first 6 weeks of lactation - during which time the ewe ingests overwintered infective larvae which develop into egg laying adults which pump out more larvae onto the pasture. It is this loading of the pasture, driven by adult ewes with inadequate worming that creates the problems of poor growth rates and high levels of worm associated diseases in the lambs. Therefore worming ewes with a conventional or even long acting wormer pre-lambing at the time of Clostridial vaccination will kill larvae in the ewe but will provide no protection in that critical first 6 weeks of lactation when the ewes are worm egg factories.
A ewe that receives Cydectin drench at lambing when turned onto dirty pasture will ingest the overwintered pasture larvae and kill them so cleaning up the pasture and reduce the future threat to the lambs.
Ewes that received a short acting wormer at lambing should be re-dosed 4 weeks post lambing. This is a critical treatment and will help keep pasture levels of worms low and help protect the lambs.
Worming strategies are moving away from annual wormer rotation with dose and move practices to targeted drenching of targeted stock with targeted product. Throughout the season we will try to drip feed the relevant information at the appropriate time.
Nematodirus
Target Drench - White drench (Benzimadazoles, try to avoid Mebendazole, old product not as effective)
Target Time - Late May, Early June when there have been reports of local risk and challenge
Target Stock- 4-8 week old lambs grazing paddocks that were grazed by lambs the previous spring.
Last year some farms did not need to treat for Nematodirus because with the mild spring the Nematodirus mass hatch on pasture occurred before lambs were grazing and the dry conditions killed them off. Conversely if you treat too early before the mass hatch then you will have to treat again. Nematodirus requires temperatures consistently above 10 degrees to facilitate hatching.
Worm Advice
Feb/March born lambs creep fed at grass are most at risk from Nematodirus due to their age relative to the risk period and due to their high stocking rate which increases the risk of concurrent Coccidiosis. The risk of Ostertagia (bowel worms) in these lambs is reduced as most will be finished without treatment before risk period of challenge in July – but only if you keep pasture levels low by strategic worming of the ewes. Group tightly according to age/control of Coccidia and pay attention to warnings of Nematodirus and dose with white drench if high risk forecast announced.
Always remember that on dirty pasture there will always be more infective larvae on the pasture than in the sheep, that these larvae cause disease and lost production as soon as they are ingested. Our efforts must be to minimise the size of the worm population on the pasture and in so doing reduce the challenge and improve productivity in the lamb.
This article was written by David Taylor from our Galashiels centre. David has been involved in further learning and research involving all aspects of sheep medicine and surgery. This Continual Professional Development is necessary to keep us up to date with current issues and enables us to keep you informed of the threats and solutions facing the livestock industries.
· appropriate grazing management to minimise the risk of challenge
· appropriate choice of product used in the appropriate way
· appropriate timing of worming
· appropriate selection of stock to be dosed
Decisions on who to treat, with what and when must be reached after:
1. Considering the risk of challenge,
2. The grazing management (past, present and future)
3. The likely susceptibility to challenge of different ages of stock at different times of year.
It is impossible to provide a worming blue print that would be applicable to all farms, to all stock and to all circumstances. A few seasonal pointers to the decision making are as follows.
· A key time in the annual worm control program is the treatment of the ewe at lambing. The worming of the ewe as close to lambing and/or turnout is critical and in most cases non-negotiable.
· Where ewes and lambs are turned onto ‘safe’ pasture (not grazed by sheep in the previous 12 months) immediately after lambing then a conventional short acting wormer can be used.
· Where ewes and lambs are turned onto dirty pasture (grazed by sheep in previous 12 months) a long acting wormer drench (Moxidectin-Cydectin) must be used.
On dirty pasture there will always be more over-wintered worm larvae on the pasture than worms in the ewes. Ewes are highly susceptible to worm challenge at the time of lambing and for the first 6 weeks of lactation - during which time the ewe ingests overwintered infective larvae which develop into egg laying adults which pump out more larvae onto the pasture. It is this loading of the pasture, driven by adult ewes with inadequate worming that creates the problems of poor growth rates and high levels of worm associated diseases in the lambs. Therefore worming ewes with a conventional or even long acting wormer pre-lambing at the time of Clostridial vaccination will kill larvae in the ewe but will provide no protection in that critical first 6 weeks of lactation when the ewes are worm egg factories.
A ewe that receives Cydectin drench at lambing when turned onto dirty pasture will ingest the overwintered pasture larvae and kill them so cleaning up the pasture and reduce the future threat to the lambs.
Ewes that received a short acting wormer at lambing should be re-dosed 4 weeks post lambing. This is a critical treatment and will help keep pasture levels of worms low and help protect the lambs.
Worming strategies are moving away from annual wormer rotation with dose and move practices to targeted drenching of targeted stock with targeted product. Throughout the season we will try to drip feed the relevant information at the appropriate time.
Nematodirus
Target Drench - White drench (Benzimadazoles, try to avoid Mebendazole, old product not as effective)
Target Time - Late May, Early June when there have been reports of local risk and challenge
Target Stock- 4-8 week old lambs grazing paddocks that were grazed by lambs the previous spring.
Last year some farms did not need to treat for Nematodirus because with the mild spring the Nematodirus mass hatch on pasture occurred before lambs were grazing and the dry conditions killed them off. Conversely if you treat too early before the mass hatch then you will have to treat again. Nematodirus requires temperatures consistently above 10 degrees to facilitate hatching.
Worm Advice
Feb/March born lambs creep fed at grass are most at risk from Nematodirus due to their age relative to the risk period and due to their high stocking rate which increases the risk of concurrent Coccidiosis. The risk of Ostertagia (bowel worms) in these lambs is reduced as most will be finished without treatment before risk period of challenge in July – but only if you keep pasture levels low by strategic worming of the ewes. Group tightly according to age/control of Coccidia and pay attention to warnings of Nematodirus and dose with white drench if high risk forecast announced.
Always remember that on dirty pasture there will always be more infective larvae on the pasture than in the sheep, that these larvae cause disease and lost production as soon as they are ingested. Our efforts must be to minimise the size of the worm population on the pasture and in so doing reduce the challenge and improve productivity in the lamb.
This article was written by David Taylor from our Galashiels centre. David has been involved in further learning and research involving all aspects of sheep medicine and surgery. This Continual Professional Development is necessary to keep us up to date with current issues and enables us to keep you informed of the threats and solutions facing the livestock industries.