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.
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.
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:
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