Breeding Soundness Exam

The Breeding Soundness Examination (BSE) is a set of recommendations put forth by the Society for Theriogenology and is commonly used by beef producers to measure bull fertility. A BSE is generally performed on sexually mature bulls by a veterinarian or reproductive physiologist. The BSE consists of a physical examination and a semen test.

Phenotype

The physical examination includes evaluating the eyes, feet and leg structure, and structure and function of the reproductive organs. A body condition score, hip height, weight, and scrotal circumference measurement are recorded. Bulls must have a body condition score of 6 or 7 on a 9-point scale to be considered a Satisfactory Potential Breeder. Some advanced facilities have begun performing disease testing and assessing sex drive and mating ability as a part of the physical examination.

The scrotum is measured to estimate the potential number of sperm cells that could be produced. Further details on measuring scrotal circumference can be found within the Scrotal Circumference page. In addition to scrotal circumference measurements, the testicles, penis, and their associated structures are visually examined to inspect for tumors, warts, frenulums, or abnormally shaped organs.

An ejaculate is collected via electroejaculation, artificial vagina, or massage to evaluate the motility and morphology of the sperm. Motility is estimated by examining the mass movement of a concentrated amount of semen. Semen with very good motility will present vigorous forward movement. Gross motility is characterized as very good (VG), good (G), fair (F), or poor (P). Individual motility is examined at 400X magnification and recorded as a percentage. Morphology describes the amount of normal and defective sperm cells within a sample of the ejaculate. When assessing the morphology of an ejaculate, technicians utilize 1000X magnification. The amount of normal sperm cells is recorded as a percentage of the sample. The BSE classifies abnormalities as either primary or secondary. Primary abnormalities describe defects which originate during spermatogenesis, which are generally abnormalities of the head, whereas secondary abnormalities originate within the epididymis and are generally less severe. Secondary abnormalities include distal droplets, detached heads, and many tail defects such as bent, coiled, or short tails.

Bulls are then classified as either a Satisfactory Potential Breeder, Classification Deferred, or Unsatisfactory Potential Breeder. To be classified as a Satisfactory Potential Breeder a bull must meet the minimum requirements of the BSE put forth by the Society for Theriogenology. The minimum scrotal circumference a bull can have ranges from 30 to 34 centimeters, depending on a bull's age. A bull must have at least 30% motility and 70% percent normal sperm cells.

Contemporary Group

Data from BSEs are not currently utilized for genetic evaluation, so contemporary grouping strategies are not provided here. BSEs are often performed for the first time on yearling bulls, and use of the same contemporary grouping strategies as those for yearling bulls would likely apply.

Genetic Evaluation

Currently, breed associations do not collect semen quality phenotypes associated with the BSE. Research shows semen production and quality measures are lowly to moderately heritable, indicating genetic improvement could be made utilizing these phenotypes as a selection criterion. For example, bulls with low semen concentration and a high percentage of abnormal sperm cells are associated with poor conception rates.

Usage

The BSE is a routine examination generally performed on natural service bulls prior to each breeding season and can initially be performed when a bull reaches sexual maturity. Currently, BSE records are typically used identify the capability of a bull to service females.