Johnes monitoring in suckler herds

[Whitepeak]

Did you get any that tested positive on blood and negative on dung?

Yes, a couple. I think the official advice was to retest, of course the cows have been out since then so we'll get them retested now they are back in.

 

[AftonShepherd]

Did you get any that tested positive on blood and negative on dung?

I had one in February that tested massively positive on blood but came back negative on dung. I've put her away fat anyway as I don't totally believe in smoke without fire. Likewise I had one cow that has been close to the threshold two years running and went away on the same wagon.

 

[M-J-G]

Keep in mind that dung tests are really only of use if an animal is further along the line of being infected.

Blood tests are to looking for the animals reaction to infection, so can be used to detect infection at earlier stages.

Without a negative blood result from further tests, I'd never keep a blood positive animal simply because it was negative on a dung culture.

 

[Northeastfarmer]

I’m sure my vet said blood testing isn’t that accurate...

 

[Hilly]

I’m sure my vet said blood testing isn’t that accurate...

False negatives but not false positives.

 

[M-J-G]

I’m sure my vet said blood testing isn’t that accurate...

True, a lot of tests aren't very accurate, but Johnes is at the poorer end.

False negatives but not false positives.

There are plenty of apparent false positives.

Apart from testing again soon after getting a negative or an animal breaks down soon after a negative result, I'm not sure how else to identify a false negative.

 

[Hilly]

How di

True, a lot of tests aren't very accurate, but Johnes is at the poorer end.

There are plenty of apparent false positives.

Apart from testing again soon after getting a negative or an animal breaks down soon after a negative result, I'm not sure how else to identify a false negative.

How do you know it’s a false positive ?

 

[M-J-G]

How di

How do you know it’s a false positive ?

When you get a positive and then test it again and get a negative, so don't cull it and it tests negative every year for the rest of its life.

 

[Northeastfarmer]

When you get a positive and then test it again and get a negative, so don't cull it and it tests negative every year for the rest of its life.

Sounds very inaccurate

 

[M-J-G]

Sounds very inaccurate

To be fair my post wasn't really an indicator of the level of inaccuracy, it's just an example of how you know you have had a false positive.

It's quite alarming how many different tests that are often taken for granted are not totally accurate and how what is deemed to be positive or negative are (to a point) open to interpretation.

 

[Johngee]

Keep in mind that dung tests are really only of use if an animal is further along the line of being infected.

Blood tests are to looking for the animals reaction to infection, so can be used to detect infection at earlier stages.

Without a negative blood result from further tests, I'd never keep a blood positive animal simply because it was negative on a dung culture.

I'm sure my vet said they only shed the germ in the dung about one day in three. I think it's a wise decision to sell anything that's blood positive, even though the scheme accepts a dung negative result as a clear test.

 

[andybk]

anyone know if the cattle johnes affects sheep , just wondering about winter keep we rent ?

 

[Gulli]

I'm sure my vet said they only shed the germ in the dung about one day in three. I think it's a wise decision to sell anything that's blood positive, even though the scheme accepts a dung negative result as a clear test.

My general thought would be that animals which have been exposed and have antibodies but not disease should be kept or you are breeding naivety into your herd. Johnes isnt a simple disease though in terms of clinical signs etc.

 

[M-J-G]

I'm sure my vet said they only shed the germ in the dung about one day in three. I think it's a wise decision to sell anything that's blood positive, even though the scheme accepts a dung negative result as a clear test.

Levels of shedding tends to be sporadic, but is very rarely at zero levels for long, the vast majority of animals that at the stage of shedding will be shedding to some degree.

 

[M-J-G]

My general thought would be that animals which have been exposed and have antibodies but not disease should be kept or you are breeding naivety into your herd. Johnes isnt a simple disease though in terms of clinical signs etc.

If you were talking about something like BVD I would agree.

But, with Johnes, how do you tell if an animal has antibody but not disease?

Particularly when you consider that by the time there are clinical signs the animal has shed billions upon billions of MAP bacteria onto the farm. Asymptomatic animals have been shown to shead disease for up to 4 years before showing any signs.

Antibody positive animals are infected and are almost certainly going to shed disease.

 

[Northeastfarmer]

anyone know if the cattle johnes affects sheep , just wondering about winter keep we rent ?

I believe it does

 

[Happy]

I had one in February that tested massively positive on blood but came back negative on dung. I've put her away fat anyway as I don't totally believe in smoke without fire. Likewise I had one cow that has been close to the threshold two years running and went away on the same wagon.

Would say you are doing the right thing.
Been testing 15+ years here. Anything massive on blood always went but did do dung on a few borderline positives for blood that then tested clear on dung only for them to show up as big positive on bloods 2-3 tests later.

Been clear for 5 years now. First years were the worst. Especially when OTMS cows were just £300 on the scheme.
At least these days you get £8-900 for a decent suckler on the fat.

 

[Gulli]

If you were talking about something like BVD I would agree.

But, with Johnes, how do you tell if an animal has antibody but not disease?

Particularly when you consider that by the time there are clinical signs the animal has shed billions upon billions of MAP bacteria onto the farm. Asymptomatic animals have been shown to shead disease for up to 4 years before showing any signs.

Antibody positive animals are infected and are almost certainly going to shed disease.

Well yes that was sort of my point.
We are stuck with a test that throws a lot of false positives and false negatives which means it takes a long time to get on top of it in a herd.
Plenty of dairy farmers now test because they have to but then dont cull animals unless they are showing clinical signs which kind of defeats the point of it but at least theres more awareness of it now I guess

 

[Chae1]

They shed more when there stressed according to our vet. We test in autumn when they come home from grass, pding cows and weaning.

 

[M-J-G]

They shed more when there stressed according to our vet. We test in autumn when they come home from grass, pding cows and weaning.

I've not seen evidence to suggest they will shed more when stressed, but it is recognised that they are a lot more likely to break down with symptoms when stressed.