A mob of sheep in a farm pen

Fly Control

Euan Tait

Written by Euan Tait

Euan is Vetlife veterinarian who
works across Central Otago.

While I am sure everyone is fast awaiting summer’s arrival and hoping for some consistent grass-growing weather, we must not lose sight of those issues that arrive with the improved climate.  

Flystrike will soon begin to rear its ugly head and, as ever, prevention is far better than cure. Maggots cause extensive damage leading to poor-conditioned ewes and, ultimately, death if not treated. On average, 80% of ewes that have been struck will be dry if kept until the next scanning.  

Good management will keep flystrike at bay, allowing your flock to thrive. Considerations to minimize the effects of flystrike include: 

  1. Dag reduction – chemical treatments and preventions will not be effective if applied to dags. Minimizing dags through crutching is a great way to reduce fly challenges on farm. Along with crutching, ensuring good nutrition, keeping animals on clean pasture, and having an effective drench plan will also decrease dag production. 
  2. Long-lasting preventative treatment – applying the right product at the right time is a vital step in prevention of flystrike. Tailing time allows a good chance for lambs to be treated with long-acting products such as CLiK™Extra, which will provide 14-26 weeks of protection. Shorter acting products (e.g. CLiKZiN™) with shorter meat withholds (seven days) are also available and will still provide up to two months of protection, meaning fast-finishing lambs can be away without the worry of withholds or being struck. 
  3. Correct application of chemicals – as well as applying the right product, we also have to be careful about how it is applied. Poor application can often be to blame for failure of chemical preventions. As mentioned before, no chemicals will work in dag-covered skin areas. For saturation dips to be effective, the sheep must be wet down to the skin in three key areas – along the back, over the rump, and at crutch level. Time must be taken to ensure adequate coverage. Monitor the sheep coming through as you go and check those key areas to make sure they are fully saturated. 
  4. Reduce the fly challenge on farm – as with any parasite, reducing the challenge can be key to minimizing the eventual harm. Any carcasses should be put in the offal hole as soon as possible. Monitoring the fly challenge is good to allow targeted application of preventative products. Moving sheep to more exposed areas with more wind can help reduce the effects of flies which prefer more sheltered environments. 

If you do have sheep that are struck, quick treatment allows for a much more successful outcome. An example treatment protocol is: 

  • Shear fly-struck wool and surrounding area.  
  • Remove as many maggots as possible and apply Maggo or Cyrex™.  
  • Monitor closely and provide affected animal with food/water/shade. 
  • If severely affected, treat with antibiotics (e.g. Intracillin®) +/- anti-inflammatory. 

If you are concerned about fly challenge on your farm or want to further discuss the best options for management and control, please do not hesitate to get in touch with your local Vetlife clinic.