About bovine TB
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3.1 Bovine TB can be passed between cattle therefore infected cattle entering your herd can be a source of infection. Introducing any new animal e.g. purchases (including imported animals) or hire bulls, or re-introducing your own stock to your herd (e.g. following a show or returning unsold from market) can be a potential disease risk.
3.2 In recent years, it has been demonstrated that cattle to cattle transmission resulting from movement is one of the main contributors to the spread of TB. For example, around 50% of breakdowns in the LRA are due to purchase of infected cattle. In the HRA, given that 84% of non-slaughter movements of cattle are to other holdings within the HRA, it must be assumed that movements are also a significant contributor to TB spread in the HRA.
Ask for TB history information before you buy new cattle
3.3 Try to obtain a full TB history of herds from which you purchase cattle so that you can assess the level of risk and take action to manage it. As a minimum, you should ask for:
i) Date of the animal’s pre-movement TB test: Not all animals require pre-movement tests, but those that do should have been tested in the 60 days before their sale. Pre-movement testing reduced the risk of undetected infected cattle spreading disease.
ii) Date of the seller’s last routine herd test: Knowing this date may offer additional reassurance if the herd has tested negative for TB recently or it may prompt you to consider carrying out isolation and post-movement testing before introducing the animal into your herd. If the last test was some time ago or you are uncertain about the testing history e.g. if the animal was not bred on the holding from which it is being sold, you should consider isolating the animal and ask your vet to conduct a post-movement test (see 3.4 below for further information).
iii) Date the herd achieved Official TB Free (OTF) status: All animals offered for sale should have tested negative for TB and come from an OTF herd. However, the length of time that the herd of origin has been OTF can be an indication of the risk level of cattle from that herd. The longer a herd has been free of TB restrictions the lower the risk and conversely a herd that has recently come off restrictions is likely to be a higher risk.
Post-movement test cattle entering the herd
3.4 Infected cattle do not usually show clinical signs of TB and will look healthy. Post-movement testing is another line of defence to detect infected cattle prior to introducing them in to your herd, and reduce the risk of them spreading TB to your other cattle.
3.5 Post-movement testing is not currently a legal requirement in England, but is recommended to reduce the risk of TB, particularly for higher risk animals. Post-movement skin testing should not be carried out within 60 days of a pre-movement test. This is because tested infected cattle can fail to react to the skin test if it is repeated in quick succession i.e. they become desensitised. This desensitisation will have subsided after 60 days and so the animal can then be post-movement tested. It is therefore recommended that this test is carried out 60 to 120 days after the animals arrive on your holding to avoid this desensitisation effect that could lead to infected animals being missed. If possible animals should be isolated until the test results are known.
3.6 Tests for TB are not perfect and a negative result does not guarantee that the animal will be free from TB. This is because:
3.7 Therefore, it is worthwhile carrying out post-movement testing even if the animals have passed a pre-movement test as it gives another opportunity to pick up any undetected infection or animals were infected with M bovis following the test e.g. during transit.
3.8 The limitations of the TB test create a particular risk in relation to bull hire. As bulls may visit several herds each year they pose a high risk of spreading TB and it would be preferable not to use hire bulls at all.
Isolate all higher-risk cattle before they enter the herd
3.9 When cattle enter your farm, it is recommended to isolate them from other cattle in the herd to ensure that they are not incubating any disease (not just TB) and to give you time to test.
3.10 If you are buying in cattle from a herd of higher TB risk status (based on your assessment of the three factors at 3.3 above), they should always be isolated. The period of isolation should be at least 60 days so that a post-movement test can be carried out before introducing them into the herd.
3.11 These recommendations apply to all cattle entering the herd, including newly purchased stock, hired bulls, and cattle that are already under your ownership but that return from being away, e.g. from shows, markets and from other premises. The risk is greater for purchased stock and hired bulls than for animals that have been off the farm for a short time. Nevertheless it is important to assume that even short spells off farm can potentially give opportunity for infection to be acquired.
3.12 The practicality of isolating cattle will depend upon a number of factors, including the number of animals purchased, their purpose (management stage) within the herd and the availability of suitable isolation facilities.
3.13 Discuss with your vet what options could be appropriate for isolation on your farm.