Making sense of mastitis

When bacteria invade, follow these simple rules to keep trouble at bay and still make profit

Peadar O'Scanaill

When an outbreak of mastitis occurs on a farm, very often we resort to fire brigade treatments as we scramble from medicine to medicine until the outbreak settles. This is often the least effective way of dealing with bacterial invasions of the cow. It is far better that we take a step back from an acute outbreak and just follow some simple rules.

Taking a milk sample for analysis is a good starting point. But one sample from one quarter of one infected cow can give a misleading result. What we should do is identify the cows with the high somatic cell count (SCC) levels. High somatic cells mean those cows are fighting an infection that's causing a lowering of the quality of the milk from that quarter.

The high somatic cell cows are losing you money and a lot of our sampling should begin with this group of cows. Ask yourself why that cow is so high in her SCC. Then kill it, cure it or cull it. Don't just hide it by dumping her milk.

The ICBF report gives us our big offenders and using the California Milk Test (CMT) we can identify the problem quarter of each cow. Sampling these cows from these quarters gives a more accurate guide as to what bacteria is causing mastitis on the farm. Correct taking of the sample is vital and is discussed later.

The sampling of the high SCC cows can be greatly enhanced by also sampling any future new cases before any treatment starts. Such samples will arise late on Friday evening or early on Sunday morning when laboratories are closed. These samples can be frozen and when five or more are collected they can be analysed as a group. This helps to keep the cost down, while still keeping a handle on any active infections.

The laboratories use very scientific methods to identify the type of bacteria and also the sensitivity pattern of the bug. Naming or identifying the bacteria can act as a compass to guide us to where the likely problem is in the herd. Some bacteria are commonly associated with parlour spread and others are associated with the sheds and bedding areas. The names can be confusing so I sometimes give them nicknames to help concentrate my attention.


Staphlacoccus aureus is a common find but we must remember that he is very commonly found on skin. Therefore, our own hands or the skin of the cows' teats may be the source and the bug may be inadvertently introduced as a contaminant during sampling. So depending on how many times this crops up in samples, we can either rule it in or out as the main cause.

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The point to note with this guy is that he is the SA in MRSA. I'll explain, Methicillin Resistant Staphacoccus Aureus is MRSA, so I call him the hospital bug and immediately I question how well we took the sample.

His first cousin is the Streptococcus family. Now there's a whole pile of them and they can be quite troublesome to treat.

One of the cousins is Strep.agalactiae and he lurks around in the parlour. In fact, most of the Staphs and the Streps are parlour poachers and use the milking machine to jump from cow to cow.

If present in the first cow up the line, then this parlour poacher can have a field day splashing down from cow to cow as that cluster goes from bag to bag.

So now we see the importance of hygiene in the dairy. Good pit hygiene holds these poachers at bay. What about pre-dipping and post-dipping? What about a communal cloth going from udder to udder? When these parlour poachers get into the system, let's do all in our power to minimise their ability to spread.

How about separating the 'somatic cell' cows into a different group where possible and milking them at the end of the milking session?

Specific advice for particular farms should be gleaned from your farm vet, but extra diligence will always pay off with regard to milking routine hygiene.

Another group of bacteria are the Enterococcus family. Their relations include E.Coli and Enterococcus faecalis. These are a nasty piece of work and are associated with faecal contamination.

They are everywhere in the bedding, the sheds, the yard and the cubicles. Hence I call them the 'cubicle kids' to focus my mind on the housing area.

They cause many cases of acute and very sickening mastitis. None of us like having to treat a case of E.Coli mastitis. Often we lose the quarter and sometimes the cow herself despite the best efforts of farmer and vet.

We see a lot of resistance in our antibiotics with some of these guys and, frankly, they are just not welcome on any farm at any time.

When we find these in our milk samples we concentrate on liming the cubicles, improving the straw bed and getting the yard scraper up to speed. One useful tip is to prevent the cows from lying down for up to 30 minutes after milking. This is to allow the natural teat seal to close fully.

In mastitis we also have that one odd bacterium, Streptococcus uberis. He can be spread in the parlour and be a parlour poacher just like his Staph and Strep cousins. But just as often he can be found bouncing around with the cubicle kids also.

He is increasing in incidence on Irish farms and can be troublesome to prevent or to treat. He can be walled off for long periods in cows with high SCC counts and only show up on occasional samples of that one cow.

Therefore, putting the spotlight on this guy via good and repeated milk samples will allow us to focus our prevention and treatment methods in the correct areas.

I look on this guy as a true transvestite because of his ability to come from the parlour or the environment. He is a real cross dresser and is seen more often these days.

Choice of mastitis tube

Once the bug is identified, the laboratory can also do a sensitivity test for us. But beware of some of these results. What works in the laboratory does not always work on the farm.

We must take into consideration what other factors are affecting the spread of the bacteria, what other infections are already on that farm and what injectable antibiotics are in use in that group of cows.

We must also decide which tube preparation is best to deliver the right active ingredient in the correct amount at the appropriate dose.

Most commercial mastitis tubes have a generic regime that fits all cases, but we sometimes must vary that, depending on what's happening down on the farm.

A simple rule of thumb is that the greater the number of samples including sensitivity, then the more accurate the picture as to what is the best antibiotic to use.

To crack the code use the following basic concepts:

  • Take milk samples from the infected quarters.
  • The more samples analysed the more accurate the result.
  • Concentrate on the milking routine when we see the Staphs and Streps.
  • Focus on the bedding and sheds when we see the E.Colis of this world.
  • Freezing samples for later analysis is a good habit to develop.
  • Allow time for the cow's teat seal to close after each milking.
  • Don't just discard the high SCC cows' milk. Identify the offending quarter via the CMT and then sample it.
  • Pre-dipping and post-dipping. They talk of 10ml of dip per cow, and not just a one-second spray of mist in the general direction of the teats.
  • Once a bacterium is causing us a problem then let's do everything to prevent it spreading. Relying on the limited range of antibiotics available without stopping the spread is entirely futile.
  • Bacterial invasion is a constant threat. They affect the quality of the milk produced and cause endless costs if allowed to spread. Keep them at bay and help make a profit out of dairying.

Irish Independent

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