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Parasite Control – Growing Cattle at Grass


Parasitic gastroenteritis (PGE) is caused by gutworms and represents a threat to the health, welfare and production of livestock. It leads to a loss of productivity in both the beef and the dairy industry: impacting weight gain, carcass quality and milk production.1 Cattle can be monitored closely through the grazing season for any signs of worm burdens. Ideally, young cattle should be regularly weighed and benchmarked against target growth rates typically 0.7 to 0.75kg/day for young stock from grass.

There are many products available to help with parasite control and it is important to discuss the best option for your farm with your animal health adviser.


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Ideal for the treatment of cattle during the spring and summer, ZERMEX® Pour-On has the longest dosing interval of 8 to 10 weeks. The extended periods between worming result in lower labour costs, reduced stress on cattle and ultimately can lead to improved growth.

ZERMEX® contains moxidectin, providing persistency for up to 6 weeks with a meat withdrawal period of only 14 days. A treatment at turnout and a midseason repeat treatment should cover your cattle until housing. ZERMEX® Pour-On is formulated in an oily solution which is weatherproof: clinical trials have shown that efficacy is not affected by rainfall before or after treatment

Residues of endectocides in livestock dung have been studied extensively in the UK and across the world to assess the impact they may have on dung-dwelling insects. These insects are important as they help remove dung from the pasture, limiting the spread of gastrointestinal parasites2 and improving soil permeability. Manure is also the breeding ground for some species of fly, so by allowing the dung beetles to remove the manure swiftly, this will decrease the fly challenge that is seen on farm.


Zermex- Cattle

How does Zermex compare and how is it different?

  • Less toxic to dung-dwelling insects – residues in dung following treatment with moxidectin are less toxic to dung-dwelling insects than residues following treatment with other group 3 wormers. This has been demonstrated in several studies in both cattle and sheep. Based on the number of insect species affected and the duration of suppression, the macrocyclic lactones can be ranked in descending order of adverse events3

  • Less frequent dosing – due to their persistence, Zermex products have a longer dosing interval against stomach worms, which means as well as being less toxic to dung-dwelling insects, fewer doses are required

When controlling cattle parasites, it is important to follow the COWS best practice principles ( to get the most effective use of cattle wormers. Target the animals that are at risk, ensure they receive the correct dose by weighing each animal check dosing equipment.

Whatever options you have in mind, advanced planning is the way to maintain good animal health and maximise productivity from grassland. This time of year is ideal for a chat with your vet, SQP or ideally both of them together, and then draw up a summer health protection plan for responsible and effective use of medicines integrated with other management techniques.


  1. Charlier et al. (2009) Veterinary parasitology 164, 70-79
  2. Sands B, Wall R. Dung beetles reduce livestock gastrointestinal parasite availability on pasture. J Appl Ecol. 2016
  3. Floate, KD et al (2002) Bulletin of Entomological Research 92, 471-481


ZERMEX® 0.5% w/v Pour-On for Cattle contains moxidectin, POM-VPS. May be prescribed by any Registered Qualified Person (RQP – a veterinarian, a pharmacist or an appropriately qualified SQP). For further information see the SPC, farmers should contact their animal medicines supplier SQP, veterinary surgeon or Downland Marketing Ltd, 15 Victoria Place, Carlisle, CA1 1EW. Use medicines responsibly: MM-08345.

4th July 2022

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