Reducing the risk of environmental mastitis in dairy cows during milking

Environmental mastitis is usually the result of infections picked up outside the milking parlour, but environmental infections can be spread during milking. Good routines and effective action during milking will help reduce the risk of environmental mastitis.

If there are bacteria from the environment on the teat ends, milking time is an ideal opportunity to get into the udder through the teat canal. Infected cows can contaminate the cluster, and infection can spread to other cows during milking.

Actions taken to prevent cow-to-cow spread during milking will not eliminate environmental mastitis, but good routines and effective action during milking will help reduce the risk.

A good milking routine is key to both the hygienic harvesting of milk and minimising the risk of infections acquired during the milking process from environmental bacteria on the teat skin. You can reduce the risk of mastitis from bacteria in the environment by:

• Cleaning the teats to remove dirt
• Using a pre-milking teat disinfectant (PreMTD) as you cannot see bacteria
• Leaving PreMTD on the teat long enough for it to kill bacteria (at least 30 seconds)
• Drying the teat to prevent a drip full of bacteria collecting at the teat end

Preparing teats for milking – washing, pre-milking teat disinfection and drying – will reduce new infections with environmental pathogens and help reduce Total Bacterial Count (TBC) and Bactoscan.

However, if cows are arriving in the parlour heavily contaminated with bacteria from the housing or the pasture, it can be very difficult to reduce the risk to manageable levels.

Why is a milking routine important?

The aim during milking is to harvest milk hygienically from the udder to produce a top-quality product and to minimise the risk of mastitis. For more details, see the Control of contagious mastitis guide.

If the udder and teats are very dirty, washing with clean water will remove dirt and allow more effective disinfection prior to milking – but this should not be necessary if the environment is well managed.

When properly carried out, PreMTD (‘pre-dipping’ or spraying) achieves a rapid reduction in the number of bacteria that are present on the skin of the teats. It greatly reduces the likelihood of intramammary infection from environmental bacteria during the milking process.

Pre-milking teat disinfection must be carried out with a product approved for use pre-milking that has a rapid ‘kill’ and should be applied for at least 30 seconds before teats are dried. Dipping is more effective than spraying.

It is important that the pre-milking teat disinfectant used is fit for purpose. It must kill the bacteria but not leave any risk of contaminating the milk. The active ingredients include chlorine dioxide, lactic acid, hydrogen peroxide and sodium dichloroisocyanurate.

The aim in cleaning is to remove bacteria from the teats. Dirt usually contains a lot of bacteria. Dry dirt and sand may be more easily removed using a dry wipe first. Wash grossly soiled teats – if teats are washed, they must be dried.

Hands and old pairs of non-disposable gloves also carry bacteria and can easily spread bacteria between cows. Clean gloves are cleaner than clean hands. A new pair of clean disposable gloves should be worn every milking.

Mechanical teat scrubbers can clean teats well, but:

• Are not proven to reduce mastitis infections
• Can be expensive to install
• Water quality must be excellent
• Need to check brushes regularly for dirt and damage, and deal with any problems immediately
• Ideally, should dry teats after scrubbing

Disposable disinfectant wipes are a popular means of cleaning and disinfecting teats before milking. The teats dry quickly through evaporation, and using one per cow will limit cross-contamination from cow to cow – but the contact time between the disinfectant and the teat skin is short and does not allow much time for the disinfectant to work.

Wiping teats dry

Where teats are washed and disinfected, they must be dried to avoid bacterial contamination entering the teat canal and the possibility of liner slip.

All wet areas must be dried with clean paper/laundered towel, with one clean/ fresh part used per teat. Disposable paper towels can be used but a good system for handling paper waste is needed.

Should I consider machine-washable udder cloths?

Using machine-washable udder cloths avoids paper towel waste and can be an effective way to clean teats and remove disinfectant. But the cloths can become heavily contaminated and cause new infections, both with contagious pathogens and with bacteria from the environment.

It’s important to consider:

• Washing machine – service contract
• Washing towels at 90°C
• Water quality
• Adding disinfectant to the wash
• Drying cloths before use
• Storage in a clean container
• Checking the cleanliness of the cloths by sending a clean cloth to a laboratory every few months for microbiological analysis

The water used to clean the parlour standings and clusters, and, of course, to wash the plant, must be human drinking water quality. Ideally, there should be no or very few bacteria in the water. Water quality is vitally important, to reduce the risk of new environmental infections from water and aerosols of water around milking time.

It is very common for bore hole water, harvested rainwater, or spring water to be contaminated with environmental bacteria. Header tanks and water storage are often overlooked – check that tanks are clean and covered, and check water pipelines for leaks and dirt.

It’s important to consider:

Methods of disinfecting water – e.g. UV treatment

• Storage of water – header tanks
• Avoid recycling water from the plate cooler back into storage

• Use a pre-milking teat disinfectant on the teats before the clusters are attached and ensure 30 seconds contact time
• Dry all teats with a clean paper or laundered towel, using one clean/fresh part per teat
• Foremilk/strip to find all new cases of mastitis as soon as practical – ideally, all cows, but especially cows in the first 30 days after calving
• Only use water of human drinking quality in the parlour – no matter how it is used, e.g. cleaning down, washing cows, etc.
• If not using mains water, the drinking water should be tested at least once a year for freedom from pathogenic bacteria

If you would like a hard copy of the Control of contagious mastitis guide or Control of environmental mastitis guide please contact publications@ahdb.org.uk or call 0247 799 0069.