A Guide To Bull Evaluations - It Pays To Test Your Bulls

Fertility is the most important economical trait to a cow-calf producer. When considering the one bull to 10,000 cow ratio of the AI sire, or the one bull to 25 cow ratio of the herd sire, fertility is obviously much more important in the bull than in any individual female. Bull evaluation is a critical component of a herd management program, and is essential if you wish to maximize your return from your cow herd.

Breeding soundness evaluation is an effective and reliable way to recognize poor potential breeders and allow for culling and replacement before the breeding season begins. It is estimated that one bull in five, taken from a random population, will be an unsatisfactory breeding animal. The causes are varied and include poor semen quality, physical defects, or lack of libido (sex drive).

A breeding soundness evaluation consists of a general physical examination, examination of the reproductive organs, and evaluation of the semen. A bull must pass all three parts of the evaluation to be classified as a satisfactory breeding animal.

Internal reproductive organs are checked by rectal exam for any abnormalities. Scrotal circumference is measured because testicular size is directly related to sperm production and fertility. A semen sample is collected by electroejaculation with a rectal probe. The rate of forward movement of the sperm is assessed and scored. The semen is then diluted and stained to allow for examination of individual sperm structure.

"It is estimated that one bull in five will be an unsatisfactory breeding animal."

The final status a bull achieves in the evaluation depends on how well he has scored in the categories above. Veterinarians will classify a bull as satisfactory, unsatisfactory or defer the classification. Standardized techniques and forms ensure consistency in bull evaluation. On occasion it may be difficult to evaluate the potential breeding soundness of a bull on a particular day. In these cases, the veterinarian may recommend re-testing at a later date.

Libido or mating ability is an important yet difficult component of breeding soundness to evaluate in a clinic. Veterinarians encourage owners to assess this at home on the first few breedings the bull attempts. Any physical defect or libido problems that prevent successful breeding will override a satisfactory breeder classification. Regardless of semen quality or quantity, the bull must be able to complete the act of breeding to be a good herd sire.

Facilities for semen evaluation should be strong, and securely confine the bull. Good footing for the bull is important to prevent him from slipping. The veterinarian will require access to the underside of the bull for semen collection. Ambient temperature should be above 10C (50F) to prevent cold shock to the semen sample and erroneous readings of scrotal circumference.

The cost of bull evaluation will depend on the number of bulls being examined and the evaluation facilities used. Prices range from $30.00 to $70.00 per bull. This cost is minimal when compared to the cost of keeping open cows, having a longer calving interval, and running extra bulls.

Breeding soundness evaluation of bulls should be an integral part of a breeding program. Your bull represents half of the reproductive potential and traits that you desire in your herd - make sure he can do his job.