By Dr Charlie Blackwood BVSc MANZCVS
50% of Bulls May Not Be Fertile.
Studies in Tasmania and south west Victoria have shown that a large percentage of dairy bulls are sub fertile – i.e. low or poor fertility!
Having fertile bulls is critical for overall fertility on most dairy.
These studies demonstrate why having a vet check your bulls before joining is important.
The bull breeding examination provided by Warrnambool Veterinary consists of:
> General examination including body condition, eyes, lameness/gait, feet and confirmation
> Palpation and measurement of testicles Palpation of internal sex organs (like our prostate)
> Palpation and visual inspection of penis
> Collection of semen with an electro-ejaculator
> Examination of semen after collection and at laboratory
> Vibrio vaccination and PI testing.
Following this examination, bulls are classed as:
> Fail – unsuitable for use in this mating
> Qualified – suitable only with many other bulls and/or they were closely observed
> Pass – suitable for use
Common reasons for failure:
> Testicle problems 5%
> Problems 28%
> Semen problems 54%
> Others – temperament, feet, etc.13%
NOTE: Approximately 50% of problems are semen problems and are only detected if semen is collected and examined by the veterinarian at the time of collection AND and expert semen morphologist.
How Do Your Bulls Rate?
> Have you got enough bulls?
> Are you bulls vaccinated, tested etc.?
> Are your bulls fertile?
Guidelines for Good Bull management:
> Have the bulls on farm 70+ days before use
> Avoid stress (nutritional, disease, transport)
> Use bulls at 3-4 bulls/100 milking cows and rotate in teams weekly
> Test bulls prior to use
> Monitor bulls during mating
> All bulls should be vaccinated for vibrio
> Consider testing to check bulls are not carriers (PIs) of Peste Virus