What are we recommending for our dairy farmers when purchasing bulls? Since the introduction of Mycoplasma bovis we have had questions from our dairy farmers about how to minimise the risk of introducing disease, and from our bull sellers/leasers about how to reassure farmers to use their bulls. This article recently went into our Dairy Talk Newsletter for our Dairy clients, so we though it would be good to share here also.
Animal movements are one of the key risk factors for the introduction of Mycoplasma bovis in dairy and beef farms. Most dairy farms we service either purchase or lease bulls for a portion of their mating period. Mycoplasma can be spread through infected semen during natural mating, so the risk is real.

Firstly we recommend having a full history of any bulls to be purchased including their electronic identification numbers, NAIT locations for all movements of these animals, and disease history for the herds and grazing blocks from which these animals have been purchased. Purchasing bulls from a closed beef farm, particularly beef units that use AB rather than natural service bulls for mating may reduce the risk of infection substantially.

Risk is increased where bulls are purchased from sales yards or youngstock units where animals from multiple sources are reared together, particularly where waste milk has been purchased to rear these bulls. Non-virgin bulls also carry a higher risk, as they have been used previously on other farms before coming to your property.

Testing is available for Mycoplasma Bovis but there are severe limitations around the test. A positive bull may not be shedding the bacterium at the time of testing, so no test can prove freedom from disease. Testing should only be done at the mob/herd level and is not recommended once the bulls are dispatched to the farms.

The lowest risk bulls are from single ‘closed’ herds with minimal history of lameness, mastitis or calfhood disease. As per our normal recommendations, virgin bulls are best and BVD status must be known from a negative blood test result and vaccination is crucial.
On arrival the bulls should be held separately from the main herd for a minimum of 7 days, during that time you should assess the health and lameness status of the bull before mixing with the herd.

Want to know more about Mycoplasma Bovis visit www.anexa.co.nz/biosecurity