July 2026 – Contain the Contagion

It has reached that time of year when Irish dairy cows have entered into the second half of their lactation cycle and with it comes the heightened risk of contagious mastitis rearing its head.

The reasoning is quite clear – contagious mastitis causing pathogens (such as Staphylococcus aureus) spread from infected cows to non-infected cows in the milking parlour. The longer animals spend time here the increased likelihood they become exposed to these troublesome microorganisms. Trying to put this genie back into its bottle can be incredibly difficult so don’t be shy in using these top tips from Animal Health Ireland. They are focused on the 3 S’s of milk quality:

Contagious pathogens like Staphylococcus aureus come from infected cows, or high SCC cows. This cannot be left to chance. You need to confidently diagnose these animals. The most objective way of knowing which cows fall into this category is through regular milk recording. It’s a laboratory technique so it takes the guess work out of finding problem cows, and without risking spreading the issue further within your herd.

If you are in a constant balancing act with your bulk milk tank SCC then you most likely have a high number of cows with persistent infections (i.e., long term >200,000 cells/ml). Persistent infection rates above 8% are usually a tell-tale sign contagious pathogens are latching onto your cows. Infection prevalence is often >15% in problem herds. You can find your herd’s persistent infection rate and infection prevalence on your ‘CellCheck Farm Summary Report’.

You should then evaluate the ‘Milk Recording and Lifetime Summary Report’ to identify the cow’s driving this milk quality conundrum. They are denoted as having a RED SCC, indicating a long-term infection, a characteristic of cow-adapted contagious pathogens. In respect to Staphylococcus aureus milk recording data is the best way to corner this bugger.

The biggest obstacle to tempering contagious pathogens comes down to mastitis detection. In many cases contagious problems present as subclinical mastitis, or to speak plainly, ‘invisible mastitis’. However, once you have identified your RED cows via milk recording you have taken the first critical step in stopping high SCC issues spreading to your healthy GREEN cows. Inspect the milk from each quarter of these RED cows using a California Milk Test (CMT) to find their problematic quarters. These are the source of your bulk milk tank woes (and are a potential reservoir of infection risking your healthy cows) and should be dealt with accordingly.

Stamping out contagious mastitis spread in your milking parlour and escaping mastitis red zones can be a difficult task but remember don’t allow yourself to get pulled in multiple directions when addressing this. There is one core concept: there has to be contact between infected cows and non-infected cows. So what is it?

• Milker’s Hands

During these hot temperatures milking pits can act as saunas without the joyous relaxation benefits. Despite this heat, every milker needs to wear gloves at all times to reduce the chances of contagious pathogens coming from them. And trust me, they’re there!

• Foremilk Stripping

A fantastic means of inspecting milk and finding evidence of clinical mastitis. However, it must be done with the utmost hygiene to ensure potentially infectious milk doesn’t get on your hands. Pay particular attention around the high SCC cows found on milk recording. Only wash strippings off the milking platform when cows have left the row.

• Communal Tissues

Wiping teats may be a common approach to cleaning teats and promoting milk let-down in your herd. But again, this can act as a conduit between high SCC and low SCC cows so avoid wiping multiple cows with the same tissue.

• Milking Liners

The only part of the milking machine in direct contact with your cow’s teats, and that could be for some 50-70 hours per lactation! In combatting SCC, they are often the first avenue people explore. Rubber liners should be changed every 2000 milkings. Use AHI’s new LinerLife Calculator to establish the optimum change dates for your herd.

• Flies

These guys love the humid environment inside milking parlours. They also love teat end damage and target leaking cows. Keep cows clean and apply fly repellents.

• Milking Machine Matters

Vacuum fluctuations are an efficient means of spreading contagious mastitis so there should be minimal liner slips and air admission into clusters. In the second half of lactation teat end damage starts to rear its head so stay alert on this. Staphylococcus aureus loves to find refuge in these cracked teats.

• Post-Milking Teat Disinfection

The cornerstone of contagious mastitis prevention. If properly applied to every teat it can reduce this issue by 50%! One of the most important things every dairy farmer does in Ireland to keep mastitis at bay. Use AHI’s Teat Disinfectant Calculator to work out how your farm is performing.

If your approaches are effective you will see Recent Infection rates in your ‘CellCheck Farm Summary Report’ fall below 7%.

·       Once you have identified the problem cows (via milk recording) and their infected quarters (via CMT) consult your milk quality advisory team made up of your private veterinary practitioner, milk quality advisor, and milking machine technician as to how to best deal with them (treatment, drying off quarter, drying off cow, culling cow, segregate group, milk last etc).

·       Get a fresh pair of eyes from this team on the milking process in your herd to evaluate the contagious mastitis red zones mentioned above. Stopping the spread of mastitis is often the missing piece on many farms experiencing problems.

·       Monitor trends in your milk recording to track how you are progressing. You want to see the number of RED and ORANGE cows going down and the number of BLUE and GREEN cows going up. Frequent milk recording can also be used to detect these invisible mastitis cases sooner, which reduces the likelihood of cows becoming chronically infected.