Diseases to keep an eye out for
High-bulk milk titres to IBR indicate infection in the herd. IBR infection in cows is permanent. Supplementary individual blood testing throughout the age groups in a herd may be necessary to define the extent of IBR infection. Management of the environment, stress and use of vaccination are necessary to control IBR.
The Animal Herd Health protocol for BVD investigation advocates using bulk milk sampling and testing for both antibody and virus. Three-monthly sampling can detect increases in bulk milk antibodies. If the BVD bulk milk antibodies are high it does not necessarily confirm that there is a persistent infected (PI) cow in the milking herd. Further individual testing may be necessary to identify PI animals by blood-testing young, unvaccinated animals from each separate group. The key to the control of BVD involves removing PI animals from the herd. Having removed these animals, vaccination supports immune protection of the herd.
This is present in 60-70pc of Irish herds. It causes infertility, abortion and depresses milk production and leads to the birth of weak calves.
Because leptospirosis localises in the kidney and is shed either continuously or intermittently in the urine, it is necessary to test bulk milk in herds three or four times a year to detect antibody trends. A spike in lepto milk antibodies may indicate recent surges in herd infection or perhaps recent vaccination. Vaccination history is essential for interpretation of results. Because leptospirosis can affect humans, vaccination is often used as a prevention strategy in many herds.
The Johne's Elisa test detects antibodies in blood and milk. Additional tests, together with the herd health history, are very important to diagnose and manage Johne's in the herd. The Johne's bulk milk test will only give a positive result consistently in a herd with a high level of infection. Beware of a negative bulk milk Johne's test. This does not mean that a herd is Johne's-free because its antibodies appear late in the disease process.