Flies cause significant welfare problems for cattle during summer months, acting as both direct irritants and as vectors of disease. Effective fly control is a welfare obligation and economic priority in cattle management.
Key Fly Species and Welfare Impacts
Stable fly (Stomoxys calcitrans): Biting fly causing intense pain and agitation; cattle cluster and stamp to avoid them; blood-sucking causes anaemia and stress in heavy infestations; disrupts grazing behaviour and reduces feed intake.
Horn fly (Haematobia irritans): Remains on cattle almost permanently; each female bites 20–40 times per day; more common in America than the UK but present; stress from constant biting reduces productivity.
Face fly (Musca autumnalis): Non-biting but feeds on eye secretions; transmits IBK (Moraxella bovis) causing infectious bovine keratoconjunctivitis (pink eye); significant welfare impact through eye pain and vision loss if untreated.
Headfly (Hydrotaea irritans): Clusters around head and wounds; vectors summer mastitis (Trueperella pyogenes) transmitted to dry cows — causes severe welfare harm, loss of quarter, and sometimes systemic illness.
Summer Mastitis Prevention
Summer mastitis is a particular welfare priority in dry cows and heifers grazing in areas with high headfly pressure:
- Stockholm tar or udder salve applied to teat ends creates a physical barrier to headfly feeding
- Fly repellent ear tags (deltamethrin, cypermethrin) reduce headfly landing time on cattle
- Housing dry cows and heifers during peak fly activity periods (July–September) in high-risk areas
- Dry cow antibiotic therapy (DCT) provides some protection but is not a substitute for fly control
Control Methods
- Pour-on insecticides: Synthetic pyrethroids (deltamethrin, permethrin) applied along the dorsal midline; effective for 6–8 weeks but resistance development requires rotation
- Ear tags: Impregnated with insecticide (pyrethroid or organophosphate); provide extended season protection; both tags in each cow for maximum efficacy
- Fly traps and sticky strips: In housed cattle; reduce stable fly burden in buildings
- Environmental management: Removing slurry and soiled bedding reduces stable fly breeding sites; muck heaps sited away from cattle housing
Pink Eye Management
Infectious bovine keratoconjunctivitis causes significant pain and should be treated promptly with antibiotic eye preparations. Affected animals should be moved out of bright sunlight, examined for ulceration, and treated with oxytetracycline eye ointment or spray. Severe or worsening cases require veterinary assessment — corneal perforation can occur in untreated cases.