Worm burdens in animals at pasture are an inevitable fact of farming in Ireland.

As temperatures increase, the time for worm eggs to develop into infective larvae shortens and when we move into June and July, there is an abundance of larvae on pasture.

Worming is essential to break the life cycle of gutworms where cattle are grazing infected pastures.

Treatments should aim to limit disease and minimise pasture contamination.

Hoose (lungworm) is an added complication in cattle. The best on-farm test for lungworm are the farmers' own ears.

Affected cattle should be treated as early as possible, because severely affected animals may either not respond or symptoms may be exacerbated, as dead or dying larvae block the lower airways and alveoli.

The low infection threshold for disease and the potential for rapid increase of infective larvae on pastures means that outbreaks are unpredictable.

Consequently, the use of clean grazing strategies is less reliable than for other roundworm species.

Clean grazing strategies include:

  • Work on the principle of keeping the cleanest grazing such as forage crops, reseeded ground or hay/silage aftermath for the most naïve animals. For example, turn out first grazing season cattle, such as dairy, dairy-cross-beef calves and autumn-born weaned suckled calves, on to low-risk pasture, eg not grazed by cattle last year. If using pasture grazed by young stock last year, implement a control plan to protect against gut worms.

  • Graze calves ahead of older animals in a leader-follower system.
  • Spring-born suckler calves that are still suckling are not likely to need any treatment for worms until later in the season. Most larvae on the pasture will be consumed by their mothers, which will be mostly immune.
  • If possible, alternate or co-graze with sheep, as most worms that infect cattle don’t infect sheep and vice versa, which can potentially benefit both types of stock through both worm control and improved pasture utilisation.

    • Strategies to reduce the risk of anthelmintic resistance include:

  • Implement the ‘test’ and ‘weigh’ approach - eg use wormers only when necessary based on performance indicators such as daily liveweight gain (DLWG) and faecal egg counts (FEC). If grazing calves have FECs >200 eggs per gramme or DLWG drops below 0.7kg to 1kg (dependent on cattle type), treatment is probably justified.
  • Monitor anthelmintic resistance: a faecal egg count reduction test (FECRT) can help to determine whether the anthelmintic use is effective. A reduction in FEC of less than 95% of the pre-treatment egg count is suggestive of a lack of wormer efficacy if the correct dosing procedure has been carried out.
  • Avoid under-dosing - eg treat the group based on the weight of the heaviest animal in the batch and calibrate dosing equipment.
  • Rotate anthelmintic classes - ie use white doses, yellow doses/injections and clear pour-ons/injections throughout the season and not just one class.
  • Implement a quarantine dosing strategy for purchased livestock – ie dose cattle on arrival and hold purchased stock off pasture for 48 hours before turning them out to contaminated pasture.

    • Parasite control plans

    To identify which parasite control plan suits their system, farmers should consider the following:

    Is help available to gather stock multiple times throughout the grazing season?

    Using products with licensed persistency (prolonged activity after treatment) can provide for labour-saving solutions by increasing the dosing interval. For example, Cydectin 1% injection and pour-on and Dectomax injection and pour-on all have five weeks persistency for gutworm and up to sis weeks persistency for lungworm. This means dosing interval can be increased to every eight weeks (versus five weeks for ivermectin-based products). Cydectin 10% long-acting injection protects cattle against re-infection with gut and lungworm for up to 120 days, meaning one treatment is generally sufficient until four to five weeks pre-housing.

    Is wormer resistance a concern?

  • Refer to strategies as outlined above.

    • Will the cattle be set stocked throughout the grazing season?

  • Will cattle be turned out on to clean pasture not grazed by other cattle in the same season?
  • Will any animals be added to the treated group during the grazing season?
  • Will cattle graze on the same pasture throughout the grazing season?

    • Answering these questions can help farmers identify an effective parasite control programme with their adviser.

    Click on the image above to view a pdf of the planner.

    Once the most appropriate option has been identified, farmers can be guided to a suitable protocol in the dosing chart and treatment dates, which will depend on turnout and housing dates, can be filled in on the chart.

    The dosing chart can be downloaded from the following link on the Zoetis website.

    With the start of the grazing season under way, now is the time for farmers speak to their prescriber and plan their grazing and worming strategies for the season.

    All Cydectin® products contain moxidectin. All Dectomax® products contain doramectin.

    Duration of persistency: Cydectin 1% injection, Cydectin Pour-On and Dectomax Pour-On: Ostertagia five weeks, Dictyocaulus six weeks; Dectomax 10mg/ml injection Ostertagia & Dictyocaulus: five weeks; Cydectin 10% Long acting injection Ostertagia & Dictyocaulus: 120 days.

    For further information, please check the SPC or contact Zoetis on 01-256 9800 or at www.zoetis.ie. Legal category LM. Use medicines responsibly. www.apha.ie.