Updated: Mar 28, 2019
Tissue tag sampling is a widespread means of obtaining DNA samples. Often determining parentage, this technology is also enhancing livestock productivity. A current genotyping programme in the Republic of Ireland is capturing DNA of 1 million cattle where genetic variations related to fertility, growth, milk yield and meat quality etc. can be identified (Source; Weatherbys). Traceability is also demanded more in the food chain and genotyping is predicted to increase.
A more current application of tissue tagging in cattle however is in Bovine Viral Diarrhoea (BVD) eradication. A highly infectious disease present in cattle worldwide and has been observed in other ruminants too (Source; AHDB). Humans cannot catch it but can spread it unknowingly.
BVD is related to Border Disease Virus in sheep and Classical Swine Fever Virus in pigs.
Several countries are BVD free and closer to home, the Republic of Ireland, Scotland and Northern Ireland are undertaking eradication programmes. In England and Wales eradication is currently voluntary with tests uploaded to the www.BVDFree.org.uk database after registration. Approximately 100,000 animals are now held with 9% of the National breeding herd involved (Source; AHDB).
BVD attacks immune systems and in young stock pneumonia, diarrhoea and fatality can occur. In adult cattle, reduced milk yield, lameness, mastitis and a host of reproductive issues are seen. Overall, poor treatment outcomes and herd health is observed.
170,000 BVD virus particles only cover 1cm and 1ml of blood can have 1 million infectious viral particles. Infection for calves is less than 500 virus particles (Source; AHWNI).
The BVD virus can be found in DNA tissue sampling as the virus wraps around DNA so tissue sampling is an ideal way of detecting BVD.
Persistently Infected (PI) animals have BVD for life and only created in utero in the first 120 days of gestation. A live PI sheds huge amounts of virus in urine, faeces, saliva, semen and blood. Many die but some enter the adult breeding herd and always produce PI offspring thereafter. Many PI’s succumb to Mucosal disease with symptoms including ulcerations in the mouth and severe scours.
Transiently Infected (TI) animals are non-PIs exposed to the BVD virus, exhibiting a wide range of clinical signs or none. If tested after they have recovered, they will show previous BVD exposure with antibodies present but not the BVD virus. They can remain in the herd and are not a source of infection unlike a PI.
Health issues in the herd may indicate BVD presence but detection of antibodies via bulk milk testing or by blood testing a young-stock sample shows any evidence of BVD exposure. This is a useful first step, however this does not tell you where this has occurred. Tagging and testing as the herd calves is popular essentially gaining two tests for one as the status of the dam is also revealed too. Tag any still born calves and ‘empty cows’ as they are highly suspicious. Tag followers and young stock. Do not assume they are BVD free.
Typifix is a reliable and proven tissue sampling tag suitable not only for BVD testing but for genomics as well. This is possible because of the superior sample preservation achieved using Typifix allowing high quality DNA extraction. This is not possible if a tissue sample is poorly preserved.
Typifix can be an Official Primary tag along with an Official Secondary tag. In addition, there is a Non-Official tag used for retrospective testing of younger or adult cattle (a ‘third’ tag). A farmer can tag and test without the need for a vet to be present although seek advice if a PI is found.
Typifix offers a simple, tamper free single step process and tags arrive ready on farm and the attached sample tab can easily be seen and retrieved if dropped whilst testing.
Typifix sample vials are sealed before and after sampling. The built-in tag counter plate also allows a cleanly taken ear sample with no cross- contamination risk.
Desiccant contained in the Typifix sample vial preserves it for up to four years and BVD virus or DNA can be easily retrieved. This is not possible with a poorly preserved sample. Other systems do not preserve tissue samples and need refrigeration before samples putrefy. The all metal applicator has longer handles than most ensuring maximum purchase is achieved when tagging.
Steps to take in you tag and test programme
Tag all your newly born calves dead or alive at the earliest opportunity but not later than 7 days after birth. Early testing reduces the risk of a calf becoming transiently infected (TI) and giving a positive virus result, even though they are not persistently infected (a TI should recover unlike a PI). Avoiding TI’s lessens re-testing. It also allows decisions to be made quickly with exclusion of any PI found. Matching a calf correctly to its dam for record keeping is also essential at this point.
Samples should be returned to the laboratory of choice ASAP, so any PI’s can be eliminated. Datamars use laboratory partners SAC to undertake sample testing and the cost of the laboratory test can be pre-purchased. SAC provide quality and accuracy in processing BVD testing.
Carry out all necessary follow up testing following the discovery of a PI animal -speak to your vet. This is necessary to identify and remove all PI’s from your herd quickly.
Accuracy is essential in BVD eradication and Typifix has seen a 99.7% sampling accuracy.
BVD Test results can be uploaded to the www.BVDFree.org.uk database in England and Wales after a farmer has registered.
Vaccination plays a part in BVD eradication alongside tagging and testing and PI removal but cannot treat or cure PI’s. Ensure breeding cattle are vaccinated prior to bulling for coverage in the first 120 days of pregnancy preventing new PI’s (as long as there are no PI breeding cattle).
If a herd is BVD free, a biosecurity programme along with vaccination of your breeding stock prevents BVD re-entering and/or new PI’s being born. Naïve herds (with no BVD exposure) are very susceptible. A useful approach to biosecurity is the 3B’s -Buying, borrowing and boundaries.(Source; Animal Health Ireland AHI).
Are stock you are buying BVD Free? Treat anything that arrives onto the farm as a potential BVD carrier (including your own stock returning onto farm).
If you think you are a closed herd, is that true? BVD can cross boundaries easily by nose to nose contact. Consider double fencing or work with neighbours to get them BVD free too