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Bull Evaluation

Bull fertility, or breeding soundness is the single most important factor to be taken into account when selecting a bull.

The primary components of bull fertility are LIBIDO (eagerness to mate), MATING ABILITY, PENILE SOUNDNESS and SEMEN QUALITY.

Tararua Breeding Centre and Totally Vets Feilding offers a BREEDING SOUNDNESS EVALUATION service.  This is a humane, comprehensive assessment of all of the above factors.  The procedure is an invaluable management aid in confirming the breeding soundness of stud or paddock bulls prior to sale, or before being turned out for the mating season.

The evaluation consists of several parts: 

Anatomical Soundness

This involves a physical examination of locomotor and reproductive organs, including palpation of the testicles and measurement of scrotal circumference.


This gives an indication of the bull's eagerness to mate (libido), and his ability to mount the teaser.  An in-oestrus teaser cow is brought into the yards.  (For a large number of bulls, the teaser cow is restrained in a specially designed portable crate.) The bull is introduced to the teaser and is allowed to mount, and the semen is collected into an artificial vagina.

There is obviously a risk, at this time, that the bulls may start fighting prior to, or immediately after testing.  To help reduce this risk, we advise that bulls be hungry on the day of collection.  This means putting the bulls into a previously grazed paddock the night before collection.  Once bulls are tested, they should be taken back tot heir paddock immediately and wither fed hay or silage  or be put onto a paddock that has an abundance of feed.

Penile Soundness

Each bull's extended penis is examined during mounting for structural soundness.  This is done to detect abnormalities such as corkscrew penis, genital warts, hair rings or damage resulting from previous injuries.

Semen Quality

The semen sample is recovered from the collection through the artificial vagina, and examined under a microscope, and given scores for volume, density, motility and morphology. 

Each semen sample must satisfy our minimum standards for each of these tests before the bull is passed fertile.

There are several factors that can negatively affect the quality of semen collected on a particular day. For example bulls that have been ridden the day before, have been fighting, or have had an injury or sickness in the recent past, may not work or have poor semen quality on testing day.  It is therefore not possible to "fail", or predict the fertility of a bull based on one isolated semen sample, assuming he passed all other facets of the test.

For this reason, bulls that do not meet our standards on their first test do not "fail" on that day, but are retested at a later date.

Facilities Required

The examination can be carried out in most stock yards.

All bulls must be healthy.

Stressful management practices such as dehorning should not be carried out within 6 weeks prior to the testing.

A QUIET in-oestrus female must be available for the test. (or several, if a larger number of bulls is to be done.)  We will arrange a synchronisation programme to ensure we have a teaser female on heat at the required time.

240 volt power and a clear bench are required within easy reach of the collection area.