Animal Health

Questions and compromises

By Rod Dyson

It is now several years since we had been to John’s* farm. Back then he was milking 600 cows in a rotary dairy and had a significant problem with clinical cases of mastitis, mostly caused by Strep uberis.

Some key changes to milking setup, dry-off management and calving management made the difference he had been looking for.

However, John recently called to say he was again having trouble with an increased number of clinical cases of mastitis, and also a steadily rising Bulk Milk Cell Count over the last couple of months.

He is now milking well over 1000 cows, has extended the dairy yard, built a shade shed, a large feed pad and loafing area, and naturally has more staff working on the farm.

It is now a really big operation and I was keen to see the changes, so when John said “How soon can you get here?”, it was very tempting to head off fairly quickly.

But that is not how things work!

The first question I asked was whether John had any recent milk culture results.

I was not at all surprised to hear that no milk cultures had been taken, and nor was I surprised when John said “I’m sure it is all environmental — it’s just like before!”

However I insisted, and somewhat reluctantly, John agreed to get some milk cultures done. It wouldn’t take long to take a reasonable number of samples and get results as clinical cases were now occurring very regularly.

A little over a week later, we were looking at the results — four samples were reported as E.coli, two were Strep uberis, four were No Growth, and two samples were contaminated.

Now this was really interesting.

While it is still a low number of samples from which to draw firm conclusions, there is a base from which to start working.

These samples had all been frozen after collection. For most mastitis bacteria in Australia, freezing is not a problem, however freezing can significantly affect the recovery rate of E.coli from milk samples.

If some of John’s “No Growth” samples were actually E.coli cases which had been affected by freezing, this would be a highly significant outcome.

Knowing we needed more samples anyway, we decided to collect samples for a few days, refrigerate them without freezing, and then submit them as fresh samples to confirm the early results.

John’s attention now turned to how he should deal with an E.coli problem.

Prevention will begin by reducing the contamination of teats with mud and faecal material.

We will need to review the management and drainage of the feed pad, shade shed and loafing areas, especially in times of wet weather which will greatly exacerbate the risk of teat contamination.

For example, will daily scarifying of these areas help the situation, or make it worse?

Then we will need to look at milking practices required to deal with E.coli contamination and risk — this will largely be about teat preparation prior to cups on.

Will John need to “wash and dry” teats? Would this be done by staff using an udder hose and paper towels, or mechanically with a teat scrubbing device? When and how often will he need to do this preparation?

Will he need to use pre-milking teat disinfection?

And, just as importantly, how would this affect staffing levels and therefore cost?

John has been on a dairy study tour to the United States and is well aware of what full teat preparation looks like!

He will also need to consider his approach to treatment, and get the best advice from his veterinary advisers.

A number of the recent clinical cases had been very severe, and a few cows had actually died.

John has also heard that some farms don’t treat E.coli infections with antibiotics because in many cases, by the time treatment begins, the bacteria have already gone and it is the toxin they have produced which is doing the damage and causing inflammation of the udder.

If he is going to treat E.coli infections differently, how will he know which cases are actually E.coli? Could he use an on-farm test or culture kit to get the answer really quickly?

And finally, John will need to ensure that he has optimal milking performance, milking routines and teat condition in the milking herd because damaged teat ends are going to greatly increase the risk from contamination and bacteria around the teat orifice.

Clearly John has a lot to consider in the near future!

He will need to work through this process with his advisery team to get the best outcome in terms of cost and results.

Almost certainly, compromises will need to be made, but hopefully it will result in a risk management strategy that is both do-able and viable for John and his farm team.

■ Rod Dyson is a veterinary surgeon and mastitis adviser at