Farm Ireland

Sunday 21 January 2018

Saboteur in cattle herds will be tackled in a national campaign

John Shirley

At last, a saboteur in Irish cattle herds is to be tackled in a national campaign. That saboteur is known as the PI. This PI is an animal within the herd that is Persistently Infected (PI) with BVD (Bovine Virus Diarrhoea).

Most PIs look like normal cattle and you are not aware of their presence. But from the moment of birth, a PI animal is shedding BVD -- potentially infecting every animal which it comes in contact with.

BVD is a most sneaky virus in that it undermines the animal's immune system. It weakens an animal's ability to fight pneumonia, scour, mastitis, and more. It is a cause of infertility; all afflictions which put stress and hardship into cattle farming.

In one form or another nearly every Irish herd has been exposed to the BVD virus. Get rid of the PIs and your BVD problem is largely solved. Herdowners who have rid their cattle of BVD, have reaped great benefits.

Other countries across the EU have eradicated BVD, or are in the process of eradicating it.

Ireland has been slow off the mark, but in a historic development Ireland's cattle industry has now come up with a plan to eradicate BVD with each herdowner carrying his/her own costs. It is reckoned that the return will repay the investment many times.

Currently, Animal Health Ireland (AHI) is holding a series of farmer meetings explaining how the Irish BVD eradication programme will proceed.

Termed the National BVD Eradication Programme, this is a three-year plan in which all calves born on the farm will be screened to find the PIs. These PI calves will be taken out of the system and the herds in which they are found will be checked for additional PIs. By doing this for three consecutive years, coupled with herd vaccination, the closed herd should be clear of BVD.

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Herdowners are encouraged to voluntarily begin the programme by testing calves born from January 1, 2012. It is anticipated that the programme will be compulsory for all herds from January 1, 2013.

The screening of the calves will be done via a special eartag which takes a tissue sample which you then send to a lab for testing. It was planned that this facility could be incorporated into the standard calf ID tag, as is the case in Germany and Switzerland, but our Department of Agriculture has put a dampener on that plan for the moment at least.

Plan B then is to order the special tissue tags along with your standard calf tags from Mullinahone Co-op for the coming season. The tissue tags will carry the same ID number as the calf tag and is inserted at the same time as the calf ID tag.

The tissue tag costs €1.55 plus €24.50 for the tagger. You can also order the tissue tags to match any unused ID tags in your possession.

Herdowners are asked to take the tissue samples within seven days of birth, store the sample in a fridge with the view to getting it away to a lab (there is a choice of four approved labs) within days.

The results will be channelled through ICBF, to which you will have given permission to handle your data.

It is anticipated that about 1pc of the calves born in 2012 will be PIs and that about one herd in four will have a PI calf.

Herdowners embarking on the BVD eradication should also look at eliminating IBR and Johnes viruses as well. The same biosecurity applies.

PI Case History

Kildare suckler farmer Heinz Eggert got a shock when he set about screening his 86 cow suckler herd for PIs three years ago. Using tissue tags supplied up to now by Enfer, he found not one but 10 PIs, including two cows, one yearling and seven weanlings. And this happened despite the herd being on a BVD vaccination programme.

While some of the PIs were below par, others looked normal, Mr Eggert told an AHI meeting in Portlaoise. Six normal looking weanlings were isolated and fed ad lib. They ate more and grew below target performance.

Getting rid of the PIs has transformed farming life for Mr Eggert, who already managed the herd better than most Irishmen. Average calving interval has reduced from 400 to 365 days. Calving spread has reduced from 12 to nine weeks. Fewer calves are hit with scour and respiratory infection but those that do get sick respond better to antibiotics. The herd has become closed, with replacements bred from within.

Questions from the Portlaoise AHI meeting.

How does a PI calf arise? A PI calf is born either from a cow that herself is a PI or from a cow that picks up transient BVD infection during months two and four of pregnancy.

Can the calf tissue test distinguish between a PI calf and a calf with Transient Infection? No. Therefore, you have the option of retesting the calves that come back with a positive reading.

At what stage should I vaccinate against BVD? The objective is to protect the foetus as well as the dam. Aim to complete the vaccination programme about a month prior to the start of the breeding season. Two vaccines a month apart are needed in the first year and once a year thereafter. A rule of thumb for a spring calving herd is start the heifers on Valentine's Day and the cows on Patrick's Day. Ask the vaccine supplier how long the vaccine will protect the foetus.

If you follow the regime for three years can you then stop vaccinating? That's the plan but the panel members were reluctant to give an absolute all clear for operating without vaccination even then. Instead, they reverted to the "consult your own vet" escape clause.

What will I do with the Enfer tags which can also take tissue samples but don't carry the official ID number? You could use them on bought-in heifers or on cows which did not calve.

How long can the BVD virus live outside the animal? In favourable conditions it can survive a few weeks.

Which is the more accurate test for the BVD virus, blood test or tissue test? Both are equally highly accurate.

I have a closed herd but need to buy a bull. What steps should I take? The bull should have been screened for PI pre-purchase. Isolate on arrival and screen him again for BVD, IBR and Johnes as well.

Why should the BVD eradication work any better than the TB and Brucellosis schemes? The tests are highly accurate. Wildlife is not an issue. Other countries have eradicated the disease in a short time span.

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