News & Advice

What will you do about bulls?

Aug 1, 2018 | Biosecurity, Dairy, Dairy Animal Health & Welfare, Dairy Farm Reproduction

Margaret Perry, Veterinarian, Anexa FVC Te Aroha

Calving is upon us, but it’s time to start thinking about your herd and heifers spring mating. Over the past months we have received the same question from farmers; what are we going to do about bulls this season? Animal movements are one of the key risk factors for the introduction of Mycoplasma bovis in dairy and beef farms. Most 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. 
There are a number of things you can do to reduce the risk of introduction of M. Bovis via bulls to your herd. When buying bulls, you need to do your homework. 
Firstly you need 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 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 seven days, during that time you should assess the health and lameness status of the bull before mixing with the herd. If you have any concerns about the bulls, contact your Vet. 
The time to source low risk bulls is now. If you would like to discuss other options for reducing the length of natural mating and therefore bull numbers on your farm, or the use of AB semen alone for mating; make sure to book in a pre-mating meeting. It’s not too early to have these discussions. 

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