Bull power

bull fertility

Mating brings with it a significant busyness with multiple mobs to manage, cropping paddocks to prepare, and the odd cow still to calve (ideally not!) and of course a mating period to manage.

Appropriate selection of healthy, well-grown and fertile bulls now will maximise your chances of running a successful bull mating period. With a payout of $9/kgMS a single missed heat is going to cost $283 in missed milk alone.

So, the most important thing about bulls…

  • Is the size of their testicles.

Scrotal circumference is a great indicator of how well the testes are functioning, with a minimum circumference of 28cm needed for yearling jersey bulls, and over 31cm, for all other breeds. If you are not keen on trying to wrap your old rusty Stanley around the privates of that angry bloke in the paddock, then try and imagine a couple of cans of Lion Red dangling away, as this is about the size you are looking for.

  • Pre-Mating examination/testing.

Bulls that are carriers for BVD will cause havoc with your mating, causing early embryonic loss, or complete failure of conception. Blood testing for this disease and vaccinating to protect bulls through the mating period should now be standard on all dairy farms. This is also a great opportunity for us to look over the bulls you intend to use, picking up any potential issues early. Full fertility exams are a step-up again and include assessments of anatomy, sperm counts and sperm viability – no use if they’re shooting blanks!

Other things to consider when selecting your bulls:

  • Bull should be in good condition, but not overfat (BCS 5-6 is good)
  • Use young bulls that are less than four years old if possible
  • Bulls should have good feet (not lame/deformed) with no injuries to their back or legs – check from behind that his legs are straight
  • Eyesight is fundamental to a bull being able to do his job – check there are no old pinkeye scars or other abnormalities
  • Virgin bulls are less likely to introduce venereal disease to the herd; but avoid using bulls that are less than 15 months old
  • Select bulls of similar size to the cows or heifers to be mated (Jersey bulls for heifers)
  • Select bulls of similar size and age and from the same mob to reduce fighting when they are in the herd
  • Observe all bulls mating over the first cycle, identify any libido, mounting or intromission problems. This is important! If in doubt, flick him out!

Managing bulls effectively is paramount to their success:

  1. Mix bulls for at least one week before going in with the cows to reduce fighting
  2. Use at least 1 bull:30 cows (and have at least two bulls in at any time)
  3. Rotate bull teams every few days – once per week at least. They need rest
  4. Keep bulls off concrete yards and ideally off races.

A note on Teaser (heat detection) Bulls:  Although we aren’t worried about the fertility of teaser bulls (there would be problems if we were!), we still need to give thought to their management as they are no-less prone to breaking down and becoming ineffective through being overworked.  A simple rule of thumb is to manage your teaser bulls in the same way as you do your service bulls. This means the ratio’s of open cows to teaser bulls should be similar (these can be pushed out slightly), rest is important and management practices still apply (ie. keep them off yards, run mobs together before mating). Don’t take your teaser for granted!

Dr Greg Lindsay BVSc – Farm Vet at Franklin Vets Kopu


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