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With mating just around the corner it is time to start thinking about bulls.  It is important to make sure that the bulls you are using to service your herd will be able to achieve the desired result.

 Bull Numbers: 

For mating yearling heifers, 4% or one to 25 is recommended especially if yearling bulls are used or animals are in hilly country.  Using less bulls removes any safety net, significantly increasing the risk of low heifer in calf rates.

For cows, the number of bulls required will depend on how many cows they are expected to service. This will depend on the size of the herd, duration of the AB period and the success of AB. A useful rule-of-thumb is the 3+1 Rule.  Multiply the expected number of not-pregnant cows at the end of AB by 3% (rounded up) and add one.  Your previous years' AB performance will be a useful guide.

See our website  www.thevetcentre.co.nz/?pid=resources  for more information

 Calving Ease:  

This is particularly important for the bulls you select to go with your yearling heifers.  Every spring we pull all sorts of enormous multicoloured calves out of heifers that were meant to have gone to a jersey bull.  Make sure you check and confirm bull details with your grazier.  Jersey bulls are the easiest calving, so even if you are going to AB your heifers it is worth considering using Jersey semen and getting a cross bred calf rather than risk them having big Friesian calves.

 Bull Soundness: 

There are a variety of tests available to ascertain if a bull is sound for breeding.  The simplest and most inexpensive is a physical exam and the measurement of scrotal circumference.  Once your bulls are put to work you need to observe them to ensure they continue to do the job well.  Lameness, back and penile injures are common and can have a severe effect on the bulls ability to carry out their task..

 Diseases:

BVD is a serious problem and service bulls are represent the greatest risk to dairy and beef herds.  Carrier bulls result in returns, abortions or the birth of carrier animals that will fail to thrive and are an ongoing source of infection to your herd. 

To prevent the introduction of BVD into your herd, bulls should be blood tested for BVD antigen and vaccinated against BVD.  Vaccination should be carried out three weeks prior to mating.  See  www.controlbvd.org.nz  for more information.

Bulls can carry leptospirosis so ensure that they are fully vaccinated for lepto.  If the vaccination status of bulls is unknown, they should be treated with Streptomycin.  Please speak to a vet regarding this.

Ensure bulls have been EBL blood tested prior to arrival on the farm to maintain your herd's free status.