a cow lying in a pen a cow lying in a pen


How to stop nuisance flies reducing your herd’s milk yield this summer

24th June 2015

Treating cows now with an ectoparasiticide will help to reduce the fly population on your farm for the remainder of the summer and autumn. Research1, 2 has shown that nuisance flies affect dairy cow productivity during warm weather, according to Fergal Morris, Ruminant Business Unit Manager at MSD Animal Health.  Fergal said June, July and August are key months when it comes to fly control and if it turns warm and damp farmers need to prepare for the worst – flies breeding rapidly with hundreds of flies becoming thousands and even millions within days.

“The weather is changing from warm and dry to warm and damp, both farmers and cows will be irritated with an increase in nuisance flies over the coming weeks and months. “

Flies multiply fast and efficiently when conditions are favourable. One fly can lay thousands of eggs, so a single fly today, which lays a thousand eggs, gives rise to approximately 500 breeding females from this. These 500 females potentially create a further population of a thousand eggs each within 10 days.  At this stage the problem is very visible and treatment is less likely to have a significant impact on the fly population.

Cows coming out of parlour

Flies are not just an irritant for cows and farmers, they also affect cow productivity – reducing the intake of grazing cows and therefore reducing yields. They can also spread disease, for example summer mastitis. ‘‘The preventative treatment approach is best when it comes to dealing with flies and this is why farmers need to take action now. It’s also important that farmers apply the treatment properly. Pour on’s need to be poured down the whole length of the back.”

Butox Pour On provides up to 2 months cover against a broadrange of flies that emerge throughout the summer and autumn months.

Butox Pour-On Suspension 0.75 % w/v contains 7.5 mg Deltamethrin per ml for topical use.

Use Medicines Responsibly.
For further information, please consult the product SPC, your veterinary practitioner or MSD Animal Health, Red Oak North, South County Business Park, Leopardstown, Dublin 18, Ireland. Tel: +353(0)1 2970220 E-Mail: vet-support.ie@merck.com Web: www.msd-animal-health.ie
Legal category: LM
  1. Bruce, W. N., and G. C. Decker. 1958. The relationship of stable fly (Stomoxys calcitrans) abundance to milk production in dairy cattle. J. Econ. Entomology. 51: 269 -274.
  2. Stork, 1979. The epidemiological and economic importance of fly infestation of meat and milk producing animals in Europe. The Veterinary Record. 105: 341-343.
  3. Haematobia irritans, Hippobosca equina, Stomoxys calcitrans, Musca autumnalis and Musca domestica

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