Parasite Watch, Sheep farming

Flies: annoying your herd, your flock and you!

By the time you notice cattle or sheep being troubled by flies, a population explosion is already taking place

Flies not only annoy your herd and flock, they can cause major economic production losses through reduced feed intake which impacts productivity. Studies in cattle have shown, the production loss caused by flies can be up to 0.3kg a day Growth Rate loss and up to 0.5l a day milk loss1. In sheep studies have shown that fly worry has caused weight loss of up to 5.5 kg over four to six days and reduced wool production has by up to 26 per cent2

They attack, irritate and feed on cattle and other animals. Flies can be involved in the transmission of diseases such as pink eye and summer mastitis. Midges also spread viruses such as Bluetongue and Schmallenberg. Blowflies are important due to the damage caused by their maggot stages.

When considering treatment, it is important to consider all species of flies that can cause disease in your animals. Ensure you treat early enough to control the rapid population growth before they start to affect your stock and treat regularly throughout the season.

Monitor fly levels

As part of Parasite Watch, farmers involved in the scheme will be using fly traps to monitor fly populations on the farm.  Fly traps will give an indication of the fly challenge.

As soon as you start seeing flies in the trap, then you know they are going to be bothering stock and you may want to take appropriate action

Farmers can share their fly problems online by tweeting a picture of their fly traps to @sheep_farmers and by using the hashtag #parasitewatch or on Facebook at SheepfarmersUK

Fly traps are available to buy or farmers can simply make their own.


How to make a fly trap

1. Take a two-litre plastic bottle and cut the top third of the bottle off.

2. Make some small holes in the end of the plastic bottle in order to allow rain water to escape

3. Invert the top of the bottle into the remainder of the two-litre bottle and seal it with clips/paper clamps to fasten it in place.

4. Place the bait, which can be made up of dog food, or an offal based product in the bottom of the bottle.

5. Hang the bottle on a fence or gate post by fixing string to the paper clamps attached to the bottle.


Treatment options

  • Fly & Lice Spot OnTM controls biting and nuisance flies for up to 8 weeks in cattle, with a zero day milk withdrawal, in sheep it will treat blowfly strike. The active ingredient has proven activity against midges.
  • DYSECT® comes in cattle and sheep formulations and gives up to 8 weeks protection in cattle, with a zero day milk withdrawal and prevents blowfly strike for up to 10 weeks in sheep.
  • FlectronTM is a season long fly control tag for cattle, offering labour savings throughout the grazing season, it has a zero day meat and milk withdrawal

Fly & Lice Spot On™ contains deltamethrin, POM-VPS. All Dysect™ brands contain alphacypermethrin, POM-VPS. Flectron Fly TagsTM contains cypermethrin (cis 50:trans 50). POM-VPS. For further information, please see the product’s SPC or contact Zoetis UK Limited, Walton Oaks, Dorking Road, Tadworth, Surrey KT20 7NS. Customer Support: 0845 300 8034. Use medicines responsibly ( Date of preparation: April 2017 AH334/17

1. Jonsson et al (1999). Med. Vet. Entomology 13, p372-376
2. Australian sheep animal welfare senate meeting 1985