Post-dip

Post-milking teat disinfection

Dipping or spraying the teats immediately after milking has been practised for many years. The aim of post-milking dipping is to remove any contagious mastitis-causing pathogens that may have been deposited on the teat surface - including any present just inside the opened teat canal - that are transferred during milking from infected milk residues from inside the liner and clawpiece, before they have chance to colonise and infect the teat. Dip chemicals also kill bacteria present on any sores on the teats, promoting quicker healing.

For the best possible effect, it is important to dip or spray immediately after cluster unit removal, before the teat canal sphincter begins to close and before any bacteria have the opportunity to colonise and multiply.

Chemicals often irritate and dry-out teat skin so both pre- and post-milking treatments have chemicals known as emollients and humectants added to counter these effects and also to soften and improve teat skin condition after milking. Teat treatment products may be available in ready-to-use form or may require dilution with water and their storage, mixing and usage instructions should be followed to achieve the best results. There are several chemical types used for both pre- and post-milking treatments:

  • Iodine-based treatments (iodophors); these are the most common products used. The iodine present in them acts like a reservoir to provide a slow release of disinfectant. They have an acidic base so require emollients to condition teat skin and avoid dryness and cracking of the skin.
  • Chlorhexidine-based treatments; these products are very effective against most bacterial species and are not as affected by organic contaminants as other types available. Chlorhexidine is an irritant to teat skin so these products contain added emollients.
  • Hypochlorite-based treatments; these are less-expensive than other chemical types but can be irritating to milking staff, can dry out teats if not used properly and their effectiveness is quickly compromised when contaminated with organic matter. They are unstable when mixed and must be stored correctly or will degrade. Sodium hydroxide is added for stabilisation but this can increase the irritant effects and emollients can only be added immediately before use.
  • Quarternary Ammonium Compounds; these products have added emollients and wetting agents to make them more effective. They are inherently less irritating to teat skin but their effectiveness against certain forms of minor mastitis-causing pathogen is uncertain.
  • Dodecyl Benzene Sulphonic Acid; these products are non-irritant, and are active against most bacteria but not bacterial spores. They continue to work well even with a high level of organic contamination.
  • Barrier dips are also used for post-milking only; they are a gel-like substance that dries to create a plasticised barrier that covers the teat and requires removal immediately before the next milking. This barrier stops bacteria from colonising on the teat surface or invading the teat orifice.

Dipping teats tends to achieve better coverage and uses less chemical than spraying, although spraying can be quicker but requires more care to be as thorough as dipping, and installing spray equipment adds extra cost. Dip pots must be cleaned out between milkings as they can become contaminated with bedding materials and faecal matter from the cows which can affect the product's efficiency. This practise is often overlooked.

There have been various attempts to automate the application of post-milking treatments to dairy cattle, where an automatic teat sprayer is mounted in a location where cows exiting the parlour are sprayed as they walk over a sensor. The advantage of this is that it can speed up the milking process but the process can have several drawbacks:

  • Depending upon how fast the cow passes through, teat coverage may be inconsistent.
  • There is an inevitable lag between cluster removal and the cow being sprayed, which is certainly less than ideal.
  • There is the potential for any muck that is deposited on the sprayer head to be sprayed onto the following cows' teats.
  • Draughts or wind flow may affect the direction of spray, depending upon where the unit is installed.

More recently, there have been developments in in-parlour automated teat dipping, where a specially designed cluster unit and teatcup/liner automatically applies teat dip as the unit is removed and then automatically flushes and disinfects itself.