Veterinary Bull Breeding Soundness Evaluations (VBBSE's)

Purpose: The Veterinary Bull Breeding Soundness Evaluation (VBBSE) is a risk assessment tool used to identify bulls that are likely to be sub fertile or infertile.

Definitions:

Fertile: Fertile bulls can impregnate (pregnant at day 42 of gestation) by natural service at least 60%and 90% of 50 normal, cycling, disease-free females within 3 and 9 weeks, respectively.

Sub-Fertile: Sub-fertile bulls can produce pregnancies but not at the rate that a fertile bull can, the chance of missed opportunity exists. Bulls that cannot achieve pregnancies by natural service, but can produce viable semen for artificial breeding, are also sub-fertile.

Infertile: Infertile bulls cannot achieve pregnancies.

Components of the VBBSE

Australian Cattle Veterinarians (ACV) uses a number of indicative components to evaluate bull fertility:

Physical- Examination of bull structure (confirmation) and upper genitalia for calf-getting ability. These are  essential elements and are standard components

Scrotum- assessment of teste tone and symmetry and measurement of them in cm's

Semen- Crush-side visual and microscopic assessment. The microscopic assessment allows us to determine the percentage of live sperm that swim in a forward motion. The figures that the ACV has adopted are a pass for bulls with >60% motile sperm and a qualify for >30% motile sperm. "If a sample is 30-60% progressively motile the bull will be a qualify and will be suitable for paddock joining but may be higher risk in single mating situations or when semen is to be frozen."

Morphology- This describes the anatomy and structure of individual sperm cells. This cannot be done crush-side with all samples sent off to approved morphologists who look at the preserved semen under a high powered microscope.

Morphology

Presented as a % of normal sperm. Bulls with 70% or greater normal sperm are likely to be fertile under natural mating conditions and there is a high probability that there semen is suitable for freezing.

Bulls with 50-69% normal sperm are very likely to be fertile under natural mating conditions however there is a risk of sub fertility which may be expressed in single sire situations or with preserved semen. Morphology testing is particularly important when purchasing yearling bulls, as morphology results can determinant of sexual maturity. 

Although abnormal sperm cells may make it to the site of fertilization, the resultant embryo will be non-viable and unable to be maintained. So the female will fail to conceive on that cycle, falling into a later calving round, thus causing a prolonged calving interval.

Alarmingly between 20-40% of bulls will fail a sperm morphology test, depending on breed. This is why it is always important to ask bull breeders for the actualy semen results rather than settling for a bull that has been "semen tested". A sub-fertile bull may still sire calves but likely will be ones later in the season, thus making them less profitable due to the decreased weight gain potential and affecting your bottom line!

The ACV strongly recommends that all bulls should be vaccinated against Campylobacteriosis (Vibriosis) and be certified as not being persistently-infected (PI) with pestivirus prior to commencement of mating.

When buying bulls always look for the Cattle Vets BullCheck logo!