Summer mastitis usually occurs between July and September, affecting dry cows and maiden heifers. Trueperella pyogenes is the primary causative agent, but infections are often mixed. It is transmitted by biting flies so conditions that promote their existence are risk factors for disease – humid and damp weather, just what we’re experiencing.

How does it present?

Typically, animals will be off their feed, appear dull and have a high rectal temperature. This will be coupled with a hard, hot, swollen quarter/s and foul-smelling yellow secretions. Less frequently, disease will not be apparent in heifers until after calving when the previously infected quarter is then identified as ‘blind’.

What is the cost of disease?

It is not likely that the affected quarter/s will recover even after treatment. Costs include loss of future milk production by around 10%, a reduction in cow value, treatment costs and an increased risk of culling. If appropriate treatment measures aren’t instigated early enough, disease can also result in abortion or death.
Depending on how many animals are affected, disease costs can be substantial. Therefore, it is important to mitigate key risk factors.

What can I do to prevent it?

Fly control

Regardless of summer mastitis, fly irritation can cause significant production losses. It is important to start fly control measures early enough in the season. When choosing a product consider how long it is expected to last and therefore when application will need to be repeated. It is also important to dose animals correctly in accordance with their weight. If animals are underdosed this will massively reduce efficacy of the product and contribute to future resistance issues. Biological control though the use of parasitic wasps is also an effective means of control. If you would like more information on this specifically, please speak to your vet or vet tech.

The environment

Over the summer months cows will choose to reside in the shaded areas of the field to get out of the sun. Unfortunately, flies also congregate in these areas, near trees, bushes, and water. Therefore, more exposed pastures are preferable during high-risk periods.

Teat sealant

Teat sealant provides a physical barrier to the entrance of bacteria into the udder. This is a very effective means of controlling both summer mastitis and mastitis caused by environmental bacteria. All milking cows should receive teat sealant +/- an antibiotic tube at drying off. This practice is less commonly used in maiden heifers due to the concern of introducing bacteria in the process. However, if summer mastitis or mastitis in recently calved heifers is a known problem in your herd, it may be worth considering. Please consult your vet to discuss this first as it may not be appropriate.