Evaluating and Reporting Veterinary Bull Breeding Soundness
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 achieve pregnancies by natural service, but not at the rate achieved by fertile bulls when
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:
Scrotum- Scrotal circumference measured as per published ACV method and reported in cm.
Physical- Examination of bull structure and genitalia for calf-getting ability; essential elements are standard components
Semen- Crush-side visual and microscopic assessment
Morphology- Standardised high-magnification microscopy of preserved sperm to assess the proportions of normal and
abnormal (shape = morphlogy) sperm by an ACV approved morphologist
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.
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.