Dexter Cattle For Sale Discussion Board

Posted: **Fri Feb 23, 2007 1:42 pm**

I am interested to see how many Dexter breeders are vaccinating against BVD or have accredited BVD free herds. We have just had our bull tested and he is antibody and antigen negative to BVD, suggesting that he has never been exposed to the virus. Our vet is seriously surprised by the results since we have a relatively poor level of herd biosecurity (we have bought stock from various breeders, have had a heifer to visit and have hired out our bull).

Posted: **Fri Feb 23, 2007 4:34 pm**

I think that the health of Dexter herds tends to be surprisingly good, possibly because of the small herd size for so many, though some which appear to be small herds are in reality part of a much bigger herd of some other breed. We also probably have quite a high rate of movements between herds and to shows, again I think the small herd size saves us a bit.

It can be tempting to assume that because someone vaccinates against a disease they have had a problem with it, but that is not always the case. For instance I vaccinate my own Dexter females because there is quite a lot of BVD in herds not too far away. I do not do the bulls in case I might want to collect semen from them, though if I am showing a bull before selling it on, ie going to a show and bringing him home before going to a sale late, I would vaccinate him before showing.

I do not belong formally to any health scheme, but keep the strictest biosecurity I can. Every year I test my young stock for BVD IBR and lepto, and test the adults for lepto and Johnes, so far with clear results since I began doing this a few years ago. I have not introduced any animals to the herd since 2000, but if I do they will be isolated till tested for these things.

It is as well to remember that a "naive" herd, ie one that has not met a particular disease, is very much at risk if there is infection anywhere near, but it is usually possible to test first to establish absence of disease before vaccinating as an insurance policy.

Duncan

Posted: **Fri Feb 23, 2007 5:47 pm**

Hi Duncan, I have an unvaccinated herd, in relative isolation. I brought in three yearling heifers in November, kept away from the rest. Asked the vet about testing for BVD and IBR, he asked me how long I had had them and said "Oh, if it's been that long and they've been ok you can safely let them in with the rest".
Yet, I keep reading about the wisdom of testing, and dont want to bring anything in to my herd. How reliable are those tests? I think I should vaccinate for Lepto, but not sure about the other diseases, in a healthy isolated group...thanks, marion

Posted: **Fri Feb 23, 2007 8:32 pm**

Hello Marion,

I do not have particular knowledge of the Canadian state of affairs, so would not want to say too much directly related to your situation. Your own Vet will know that best as long as you are both communicating well.

Generally there seems little point to me in worrying about bringing in disease unless you know you are free of it in the first place. It is not always easy to know if a particular infection is present in a herd.

If you are free of BVD, the risk of introducing infection comes from (a) contact with active infection which has been recently acquired by the introduced animals.
(b) contact with a persistently infected animal, which may in the early stages be free of clinical signs
© introduction of a pregnant female carrying a PI (persistently infected) foetus.

A BVD PI is the result of the foetus aquiring infection during pregnancy and as a result not recognising the virus as "foreign". They are in effect virus factories, turning out large amounts of virus all their life. The life is often shorter since they often develop the "mucosal disease" phase and die - see another thread on this board on that subject.

If animals are bought which have acquired the infection recently and are what could be termed "transiently infected", then quarrantining for a few weeks would get rid of the risk, as long as none of them are pregnant. If any are pregnant then there is the risk that the foetus may be carrying the infection and spread it after birth. Or if one of the introduced animals is itself a PI then trouble will follow. Persistently infected animals are best picked out by testing for antibodies, and if that is negative, then test for antigen. The antigen test is looking for evidence of the actual virus itself, not antibodies. PI animals are always antibody negative/antigen postive after enough time has elapsed for any maternal antibody to have gone. Yearling heifers should come into that category - if they are antibody positive they have either been vaccinated or encountered the infection. If they are antibody negative and you want to be absolutely sure they are not carriers then you need to do the antigen test. However if they came from a known source then it may be that the risk is very low.

IBR infection is a different beast altogether from BVD. There are many strains of IBR producing a spectrum of signs from purely respiratory with runny eyes, nose, cough, clogged up trachea etc, to strains where the reproductive signs predominate and abortions result. In my part of Scotland up to date we have really only seen the respiratory form, though this year one farm has had a combination of respiratory signs and abortions in commercial dairy cows. The main difference in the way the infection behaves from BVD however is that once an animal is infected with IBR it remains a carrier. The symptoms subside, but the virus lurks and can be shed again especially after stress. So if a herd has already had IBR infection at any time, there are likely to be individuals present which carry the virus. But if your herd has been free of IBR, and you buy in a carrier, then you may get trouble at some time later and not realise where it has come from. Any animals which test positive for IBR antibodies will carry the virus unless the antibodies come from vaccination. Nowadays there is a vaccine specially designed to produce antibodies a little bit different to the real thing so we can tell the difference, but most of the vaccine used produces antibodies indistinguishable from the real thing. Normally I would not panic at the thought of introducing an IBR positive animal to a herd which already has the virus in it, but if you are genuinely free of it and wish to remain so you have to test for antibodies. If they are produced by the newer vaccine they will be distinguishable from infection, but if you cannot tell if the antibodies are from vaccine or infection then you have to assume they are from infection.

Sorry this all sounds so complicated, but that is the way it is.

Leptospirosis is a much less clear cut infection in terms of getting rid of it by vaccination. Vaccination will reduce shedding, may prevent new infections, but will not necessarily get rid of infection that is already established. It would probably be wise to test the whole herd first to see what the situation is before using any vaccine. There is little doubt that using vaccine reduces the risk of new infections within the herd, and some vaccines have strong claims for reducing the shedding of bacteria from infected animals. Serious attempts at erradication often involve treatment of the whole herd with antibiotic such as streptomycin, it can all get very complicated.

All this vaccination needs careful thought, especially if you are likely to want to collect semen, or export any individuals. Always have an in depth discussion with your vet on the subject, don't just rush into things.

Duncan

Posted: **Fri Feb 23, 2007 8:48 pm**

Duncan,
Thank you for the advice. I hadn't considered the semen possibilities, but if we are to keep our herd closed then we may well chose to sell our bull's semen.

I would still like comments from other Dexter breeders (especially in the S England) about their current BVD status. I am generally interested to see how many people out there are considering or have already vaccinated their animals. Given how often Dexters seem to move between local herds, there must be a potentially high risk of an outbreak of BVD within the Dexter world.

Posted: **Fri Feb 23, 2007 8:57 pm**

I certainly did not want to discourage the original purpose of this thread, ie to find out where people are in relation to BVD. Getting reliable statistics is very difficult, but it would be good to know what is going on. Some will know what their herd status is, some will not. Some will be free, but vaccinated, some will be free and unvaccinated. Some will have some infection and be using vaccine to limit it. some will be doing nothing. I have thought about trying to devise a small questionaire to post, but the results will at best be interesting, certainly not scientific. They will be skewed according to what people are willing to reveal, as everyone will not necessarily feel like being open about the subject. But it would be good to have some discussion on it, and input from lots of folk other than me. So come on folks.

Duncan

Posted: **Fri Feb 23, 2007 9:03 pm**

Thanks Duncan, but Oh Dear!, I will have to digest all that after I have cleaned the freezer ready for this years steer meat

The local vets say "just vaccinate", and dont have much time for explanations. Never had a sick animal or an abortion, but they say Lepto is prevalent (from deer urine in pasture). Have read and been told that PI animals are usually ne'er-do-wells? That was my worry - healthy looking animals that could be PI. I bred them AI the first month here.
The rest of the animals were born here and have had no exposure to other cows. Foundation cow has calved every year, five for me and two since sold, and due again this year, and always appeared very healthy..marion

Posted: **Sat Feb 24, 2007 12:30 pm**

I had our two bulls tested and a bull calf. The two bulls had had contact with BVD in the past because they had antibodies, but tested negative for the virus. The bull calf was negative for both, so we were advised to immunise the bull calf before it was sold to a dairy farm for use on their heifers.

Since the bulls are negative for the BVD virus and they have been with the same cows in the herd for years, I'm guessing that the cows are fine as well.

The bulls have been leased out this season, but on returning, will be keep in a couple of paddocks separate from the herd, for the Winter. I think that, as there will be no contact with the herd for the next 9 months, that any infection they pick up, should be out of their systems by the next mating season in December? Would that be right?

Posted: **Sat Feb 24, 2007 4:25 pm**

Hi Farrant,
Until this morning I did not feel testing was neccessary, but on checking my cows discovered one of my senior cows had in the middle of the night had a calf that was dead when I found it, whether it was born dead I do not know, but she was not due until 19th March. So the vet was called and tests have been done to find probable cause. He is not unduly concerned as the herd was tested for bruselosis only 14 months ago and there is no known disease in our area, and expects results to be negative for the nasties. I have disscussed with him about what we should be doing and we are to arrange a further meeting to discuss how far I would like to go with the testing. He is going to test the samples taken (including the calf) which should give some indication on our health status as all of my cows are from the same foundation cow who is still in the herd. I hope there is nothing in particular wrong with the cow as although she is now in her teens always produces and looks after a very good calf, thw of her daughters are due to calve next month and a further daughter is due to run with the bull in June.
Martin. (Medway Valley Dexters)

PS Although Coopers are closing I was contacted this morning as the slaughter house and cutting room has now been leased by someone and Mick the slaughterman is still going to be there. So I have booked my two steers in for March 20th.

Posted: **Sat Feb 24, 2007 7:56 pm**

My bull must have been exposed to BVD when he was at his first show. I decided to take semen from him and antibodies were found but as it was inactive this did not impede semen being taken. That would have been disasterous if it had been IBR as it would be impossible to take semen from bulls from a herd which has ever had IBR (this for export of course don't know about taking semen at the farm for own use.) Subsequently after his return home, I had a heifer which did not calve so had the young stock was tested and all were negative .. except the heifer which didn't calve. I take it that she was infected when put with the bull. Now I have no active BVD in the herd and most are totally clear but I have been advised to vaccinate the lot by the vet. Last year I vaccinated the animals going to a show only but one has no idea about the health of neighbouring cattle, as Duncan says.
The good thing is that the vaccination does not affect the foetus so it can be done during pregnancy ... hope my vet is correct Duncan!
Jo

Posted: **Sun Feb 25, 2007 12:40 pm**

Martin, got my fingers crossed for you. Good news about the slaughter house. I'm just trying to think of how to make my millions out of all this rain wev'e been having, but no joy yet!

Posted: **Mon Feb 26, 2007 3:13 pm**

Inger asked about bulls being clear of active BVD if isolated after return from hire work, and if the isolation is for several months this will be true. But not all infections they might pick up will be transient like BVD - if they encounter Lepto, IBR or Johnes the story will not be so happy.

Duncan

Posted: **Tue Feb 27, 2007 5:19 pm**

Duncan, could manure carry any of these diseases to another farm? I am thinking of the practise around here to buy liquid manure from dairy farms for fertilizing fields. When I talked to my dairy farm neighbour, he mentioned "seeing" Jhonnes (sp?) in dairy herds in this area but didn't comment specifically. I asked my vet if there was anything in particular I should vaccinate for or be concerned with, and he said no. I don't show my animals and do know that the kids in the 4H always have to have their cattle vaccinated in order to go to shows so somebody must be worrying around here but it isn't the dairy farmers or the vet!

Is there a reliable test for Jhonnes?

Posted: **Mon Mar 19, 2007 2:11 pm**

Good news last week, was informed by my vet that the cow that aborted has tested clear of BVD, IBR, letospirosis and all other nasties, and the reason for the abortion is unexplained leaving just mechanical reasons or as we laymen say 'just one of those things'. As a snapshot of my herd health its a possitive result and I will have to think seriously as to where I wish to go from here.
Calving has not been easy yet as my fears for one young cow that wasn't spotted bulling last year have proven correct and she is not in calf. One of the maiden heifers had twin bull calves, the first a breach, which resulted in both being born dead, expectations dashed, and dissapointment for the whole family. I now have four left to calve and three that I will have to try and stop getting too fat before the bull goes in. Makes you appreciate the easier times.
Martin.

Posted: **Mon Mar 19, 2007 10:46 pm**

Manure could carry quite a few infections eg Johnes Disease, Salmonella etc.
Johnes can be diagnosed from a blood test or from examination or culture of faeces. The blood test is not 100% reliable, and usually does not show up a positive animal for years, eg infected at birth, not positive on serology till over 2 years old. If using blood tests for screening it is usual only to test those over 2 years. Examination of faeces is a time consuming and not very reliable test, and culture takes over 4 months before a result can be declared. When this is taken in conjunction with the very long, years, incubation period, and the persistence of infection on pasture, it is easy to see why Johnes disease is such a difficult one to erradicate.

Duncan