Selecting the "perfect" bull
Bull selection consists of a balance between information and phenotypic evaluation
By Beth Ellen Doran
It looks to be another year with an ample supply of bulls for sale and no shortage of data. The challenge is sifting through the information and sorting through the offerings to find “the bull” for your operation. A logical place to start is with your herd and what you intend to do with the calves. Will you retain ownership or sell them? What is their intended purpose – breeding or market? Which traits are important to your cowherd?
Important data includes: 1) actual numbers for birth, weaning and yearling weight; and 2) Expected Progeny Differences (EPDs). Both are useful, but EPDs are only available for registered bulls and not all breed associations utilize EPDs.1 However, actual numbers may be available.
EPDs are statistical calculations that predict how well a bull or cow will perform for certain traits, and cow-calf producers can use them to compare the genetic potential of different animals within the breed. All breed associations that have EPD’s report four traits – birth weight, weaning weight, yearling weight and milk.2 Breed associations might report EPDs for additional traits such as calving ease direct, scrotal circumference, various carcass measures, disposition, longevity, value indexes, etc. Each trait has been deifined.3 But a breed association may not have EPDs for every trait. To determine the traits an association includes in their genetic profiles, buyers should check with the respective breed association.
In addition to listing EPDs and a history of parentage, pedigrees for registered bulls may provide information about potential genetic defects. The bull and his ancestors may contain two letters beside their name designating the genetic defect and if they have tested free (F) or are a carrier (C).4 When in doubt if a bull is genetically “clean,” contact with the respective breed association for their listing of genetic defects that have been identified and the results of testing for the defects.
The Breeding Soundness Exam (BSE) is an assessment of a bull’s fertility that should be conducted by a veterinarian 30 to 60 days prior to breeding. It involves a physical exam, an evaluation of sperm motility and morphology, and a reproductive tract exam. The bull must meet minimum requirements for each part of the BSE to be classified as satisfactory.5
Phenotypic evaluation While the data and information mentioned above are critical factors in bull selection, phenotypic evaluation should not be overlooked. EPDs have not been developed for all traits – leaving evaluation to the “eye” of the buyer. Following are examples of phenotypically important traits.
A bull must be structurally sound to travel pastures and withstand the rigor of breeding females. Score cards have been developed which evaluate foot angle, claw set and rear hock angle, but only the American Angus Association has an EPD for foot angle and claws set.6 Currently, there are no EPDs for slope of the shoulder, “heaviness” of bone, or foot size.
Pay particular attention to the position of the bull’s scrotum and symmetry. A “twisted scrotum” is abnormally rotated and technically referred to as “testicular torsion.” A minor twist results in a slightly sideways suspension and may not affect reproductive performance. But it is abnormal in conformation and visually unpleasing. A major twist may indicate structural defect and reduced fertility.7 Abnormal testicular development can also cause low fertility. Testicles should be symmetrical, the same size, and freely movable in the scrotum. Small size or degeneration often affects only one testicle. However, sperm production in the smaller testicle may be impaired.8
Evaluate levelness of hip in the bull. Usually, a level hip is longer and more muscular. Producers may defend a minor slope from hooks to pins in females, citing easier calving and expelling of afterbirth. However, when the pins are higher than the hooks, there is the potential for calving difficulty and retained afterbirth. Avoid selecting bulls with this structural problem and perpetuating this trait.9
Last, but not least, select bulls with good dispositions. Docility is heritable and desirable for your personal safety and its positive correlation with average daily gain, marbling, and cattle health.10 Some breeds have or are developing an EPD for disposition. Others may not have this EPD, which leaves evaluation to breeder input and buyer judgement. Producers often refer to balanced EPDs. One could argue that bull selection consists of a balance between information and phenotypic evaluation. Both are important and necessary to find your “perfect” bull!
References:
Kuehn, L. and M. Thallman. 2022. 2022 Across Breed EPD Table and Improvements. Beef Improvement Federation.
Hammack, S. P. and J. C. Paschal. 2009. Texas Adapted Genetic Strategies for Beef Cattle VIII: Expected Progeny Difference - EPD. Texas A&M AgriLife.
Spangler, M. L. Revised 2011. EPD Basics and Definitions. University of Nebraska-Lincoln.
American Angus Association. 2024. Breeders Reference Guide. p. 58.
Bedford-Guaus, S. J. Modified 2024. Breeding Soundness Examination of Bulls. Merck Veterinary Manual.
Sitz, T., T. DelCurto, and M. Van Emon. 2024. Foot Scoring of Beef Cattle. Montana State University.
Sprott, L. R., T. A. Thrift, and B. B. Carpenter. 1998. Breeding Soundness of Bulls. Texas A&M AgriLife.
Boyles, S. The Bull’s Scrotum and Testicles. The Ohio State University.
Daniel Jr, D. L. and L. A. Kriese-Anderson. 2013. Beef Conformation Basics. Alabama A&M and Auburn Universities.
Comerford, J. 2022. Effects of Docility in Beef Cattle. Pennsylvania State University.
Doran is a beef specialist with Iowa State University Extension and Outreach. Photo credits: Iowa State University
