As we approach the end of another year we are continuing with TB testing around the breakdown in Bootle, hoping that no problems are found and that the need to pre-movement test will be removed. We are also doing the 6-month tests in the herds that have been caught up in the breakdown at Grizedale, with these herds needing another test in 12 months time. (Just a reminder to all of you that routine testing should be done in your herd every 4 years, and this now means we have to test all breeding females as well as those over 6 weeks of age that you intend to breed from). We also need breeding bulls. A large number of you have been in a radial zone until recently and may not be expecting a test for 4 years, however in order to maintain some surveillance in the area a random number of farms will be tested each year for the next 4 years, so some of you will have the dubious pleasure of a test again this year. We have also been carrying out some tracing tests—these are done on animals that have come into the area and their farm of origin has subsequently gone down with TB. It is worth trying to make sure any animals you buy are from a disease free area if possible, there is a website www.ibTB.co.uk which will give you up to date information on TB outbreaks across the country. There is also another website you may have heard of which gives some advice on ways to reduce the risk of TB entering your herd www.tbhub.co.uk.
BVD is also a topic of interest to some milk buyers, with Sainsburys requesting herd testing to check for evidence of infection. In most cases this testing involves taking a sample from the bulk tank to check for virus as well as blood samples from 5-10 heifers 9-15 months old to see if they have been exposed to the virus. The aim is to find and remove the carrier (PI or persistently infected) animal as this will be spreading the virus around the herd. Herds in Scotland have already done this testing to try and have national herd free from BVD—any positive animals are not allowed to be sold except for slaughter.
When a pregnant cow sees the virus for the first time she can give the infection to her unborn calf, causing abortion, a dead calf or a PI calf that looks perfectly normal. This PI calf is then a source of infection to all other cattle on the holding. It will reduce the immune response of other calves making them more susceptible to pneumonia and scour, and if they infect a pregnant cow for the first time then her calf is also likely to be a PI animal. Some of these PI calves may then develop mucosal disease (scour, lameness, become ill thrifty and die). Removing these PI calves should help improve the overall health of your herd.
One way to check for these PI calves is using tissue tags. Most tag manufacturers have a contract with a lab that will test samples for BVD virus. When you tag the calf then it will take a sample of tissue from the ear which you send to the lab. They will test it for BVD virus and if negative this will confirm that this animal is free from BVD– you can use this result when you want to sell it, especially if it goes for breeding or it goes into Scotland. If the calf gives a positive result it is a PI animal and is best to be disposed of.