Introducing a stock bull, whether it is the main breeding sire or a sweeper, can be a risky process, according to North Yorkshire vet Mark Spilman.
Mr Spilman, a partner at Bishopton Vet Group, says farmers need to plan well ahead to prevent disease, cut safety risks and avoid buying a dud.
A mature stock bull poses a distinct safety risk for people working on the farm. This means facilities should be adequate to house, manage and handle the bull without putting human health and safety at risk.
All of the equipment, pens and housing must be carefully designed to contain the bull and allow it to perform without injury.
The design and construction must also allow staff to control and manage the bull without risk to their safety.
For specific advice on handling and housing bulls read the HSE pdf (page 4).
Many herds will breed all their own female replacements, so the bull is the only animal that is brought on to the farm. It is therefore essential that he is not going to jeopardise the health status of your existing breeding herd.
Essential health checks required prior to purchase include:
Bovine tuberculosis (TB) Establish the testing interval of the herd of origin. Buy from a four-yearly testing area if possible.
If this is not possible then pre-movement testing will be required and a post-movement test would be advisable to minimise risks of introducing disease.
Johne’s disease The health status of the bull’s herd of origin must be obtained. This will provide more information than testing the bull itself (certainly if he is under two years old).
Buying from herds where Johne’s disease is present should be avoided. Ideally purchase bulls from herds who test annually as a minimum and are accredited with the lowest CHeCS risk status – R1.
Bovine viral diarrhoea (BVD) The bull should come from a BVD accredited herd. If not, the bull should be blood tested for the presence of BVD virus and BVD antibodies before purchase.
If the bull has not been vaccinated then he should test negative for both. If he is antibody positive without previous vaccination this shows he has been exposed to wild BVD virus and there is a chance he could still be shedding virus in his semen.
If you vaccinate against BVD in your herd you should restart his vaccination before using him so that you know he is up to date.
Infectious bovine rhinotracheitis (IBR) The bull should be tested for IBR antibodies using a test that can differentiate between natural exposure and marker vaccine-induced antibodies.
Bulls with antibodies (gE) to indicate natural exposure will remain infected for life and will shed virus when stressed. If your herd is negative for IBR then you should not buy an IBR-positive bull.
If there is already IBR present in your herd ensure that the bull is vaccinated before coming to the farm.
Leptospirosis The bull should be tested for leptospirosis antibodies. The test does not differentiate between natural exposure and vaccine-induced antibodies.
However, it is still worth testing. If a bull is antibody positive and you know he is not vaccinated he is potentially a risk to the new herd as he could be a disease carrier.
Therefore, if the purchase is to proceed then vaccination should certainly be performed and, dependent on the risk assessment performed in conjunction with the herd vet, treatment with appropriate antibiotics should be given. It is also advisable to keep the animal in quarantine.
Campylobacter This is a venereal (sexually transmitted) disease and therefore buying a virgin bull is the best way of minimising the risk of buying in campylobacter.
Testing is possible but false negative results are common, so if he has worked previously then getting your vet to perform an antibiotic sheath wash will reduce the risks.
Liver fluke Knowing the liver fluke status of your herd and the herd of origin of the bull is important. If there is fluke present in the origin herd then quarantine treatment with a flukicide that kills immature and adult fluke is necessary.
Digital dermatitis To avoid introducing digital dermatitis into your herd, source from a herd free from infection. Foot-bathing the bull while in isolation with 5% formalin will help minimise the risk of introducing the bacteria to the farm.
Even after these checks a standard quarantine process should still be adhered to, giving time to treat internal and external parasites.
Bull performance checks
You should also check that he is going to be able to perform as a stock bull, by having a breeding soundness examination performed on him before purchase.
This is an essential procedure as more than 20% of stock bulls will be sub-fertile and can reduce fertility performance of the herd.
The procedure involves a thorough physical examination and evaluation of his mobility and legs, as lameness is a very common reason for culling stock bulls.
A detailed examination of internal and external genitalia is also performed, looking for evidence of infection, inflammation and swellings.
Scrotal circumference is measured and is an important factor in assessing the amount of work a bull may be capable of, as it is directly proportional to his sperm producing capacity.
A semen sample is assessed immediately post-collection on farm, under a heated microscope.
More detailed evaluation of sperm morphology (shape) is then performed back at the practice. There are British Cattle Veterinary Association endorsed minimum standards that bulls have to fulfil to be classed as “fit for purpose”.