SUMMER mastitis is defined as intramammary infection of the non-lactating udder, and is a common problem in the UK in both dairy and beef herds especially if they are dry in the summer months. Heifers can often be affected as well.

During the acute phase of the disease, a cow will typically show an enlarged udder often producing putrid material. The cow is often lame due to pain and swelling. In these cases the animal may be depressed and can die due to the presence of endotoxins. Animals that recover will inevitability lose that quarter.

In less severe cases, the first indication of a problem may be the udder has a blind quarter with a hard central core of fibrous scar tissue.

The disease is generally involves a variety of bacteria most of which have a widespread presence in the herd.

Transmission of infection is mainly due to the vector activity of the sheep head fly, Hydrotaea irritans, which is commonly found around livestock in the summer months. Other factors include trauma and irritation of the udder and teat sucking can be a factor.

Treating summer mastitis

Unfortunately, no treatment will ‘save’ the quarter but a vet will normally prescribe antibiotics and anti-inflammatory to help the animal recover as quickly as possible.


Management of dry cows and heifers plays a pivotal role in the reduction of summer mastitis incidence. Some farms may have a particularly high incidence – most likely due to ideal conditions for flies being present on that farm.

Avoiding particular problem pastures, especially sheltered areas near woodland, can be very useful. Exposed areas, particularly on windy ridges, generally have a lower fly population.

Good pasture management also has a role to play. Poor pasture with a lot of thistles and nettles will cause scratching and udder irritation. Using a topper and herbicide sprays should help reduce the udder trauma and so the incidence of mastitis.

Pour-on fly preparations, generally those containing permethrin, are recommended for vulnerable groups. During times of heavy fly challenge – usually July to August – reapplication of insecticide may be indicated, typically on a four-weekly basis. You get better results if product is applied early in the season.

More traditional topical products, such as Stockholm tar, may be helpful in deterring flies, but need weekly application to be of use. External teat sealing preparations, supplied as a dip that dries into a flexible coating, are of limited use unless repeated frequently which may not be an easy option with dry cows.

Intramammary products for summer mastitis prevention are very useful but with the pressure to decrease antibiotic use – and with prevention achievable via non-antibiotic measures – it is difficult to justify this use.

Internal teat sealants have been proven to be beneficial in the reduction of infections in the non-lactating udder, which is also true of the summer mastitis. Prevention does, of course, depend on the formation of a proper plug in the infused teat so speak to your vet about the best product options for you.

In short, every year summer mastitis causes severe economic loss in both dairy and beef herds in the UK. Both grazing management, using the correct treatment protocols and veterinary intervention have a role to play in reducing these losses.