Ryan Sproul

Well I hope everyone is enjoying this nice weather we have been getting. I think we were close to setting a record high temperature on Sunday. This time of the year, many of you have been getting those bull sale catalogs in the mail and maybe have even went to a few and even bought a bull or two.

With numerous herd bulls purchased at this time of year, this week’s column is a reminder for commercial cow-calf producers that scrotal circumference is a trait that should be included in their bull selection criteria. While there are many others to look at too, this should be one of the top ones on the list. Studies indicate that the probability of having beef bulls with satisfactory semen quality increases greatly as scrotal circumference increases from 30 to 38 cm. Many sale catalogs will list an adjusted scrotal circumference. This is an age adjusted measurement that allows producers to evaluate yearling bulls. In Angus, for example, scrotal measurements should be taken when the bulls are between 320 to 440 days of age and are adjusted to 365 days of age for reporting in the catalog. Scrotal circumference is highly correlated to total sperm output and moderately correlated to normal sperm morphology. Bulls with larger testes will produce more normal sperm cells. Selecting bulls with large testes also has the positive effect of improving fertility of the daughters produced. Bulls purchased at auction are normally “guaranteed breeders” meaning that the bull has passed a Breeding Soundness Exam (BSE) administered by a veterinarian. A BSE includes a physical examination (feet, legs, eyes, teeth, flesh cover, scrotal size and shape), an internal and external examination of the reproductive tract and semen evaluation for sperm cell motility and normality. Be sure to study those sale catalogs and look to see if the bulls passed a BSE. Herd bulls on the ranch should also be given a BSE prior to spring turn-out. Sound feet and legs are very important as bulls need the ability to travel and mount for mating. The external examination of the reproductive tract includes evaluation of the testes, spermatic cords and epididymis. Examination of the external underline during semen collection will detect any inflammation, foreskin adhesions, warts, abscesses, etc. The internal examination is conducted to detect any abnormalities in the internal reproductive organs. The semen evaluation is done by examining a sample of the semen under a microscope for sperm motility and proper shape. The table below illustrates the minimum scrotal circumference that will allow a bull to pass a BSE. However, bull buyers should not be anxious to accept the minimum, but rather select bulls that are average or above average for the breed and the age of the bull. Therefore, the “Good” column of the following table is a better guideline for bull selection. Brahman influence bulls mature later and will have smaller testes at younger ages. If you need more information on this or any other subject, please contact us here in the OSU Extension Office at 918-253-4332. Have a good week, and maybe I will see you at some of the upcoming bull sales!!

Oklahoma State University, U.S. Department of Agriculture, State and Local Governments cooperating. The Oklahoma Cooperative Extension Service offers its programs to all eligible persons regardless of race, color, national origin, religion, sex, age, disability, or status as a veteran, and is an equal opportunity employer.