Bulls provide the biggest proportion of calf crop genetics, so it is important to select a herd sire that can produce desired offspring.
Basics to consider in selecting a bull include breed type, parentage (pedigree), physical appearance, performance records and genetics. Each one of these factors was discussed by Joe Paschal of Texas A&M AgriLife Extension during the 2018 Texas A&M Beef Cattle Short Course. The information in this article is taken from Paschal’s presentation, unless otherwise noted.
There are more than 60 different breeds of beef cattle in the United States, so choosing a breed of a bull can be a daunting task. Fortunately, most of the breeds in Texas fit one of five groups: British, continental beef, continental dual purpose, Brahman or American. The breed selection process is simplified first by choosing a group that can meet ranch production and marketing objectives and then selecting a breed within the chosen group.
Production levels of the major breed types in Texas are shown in Table 1.
Physical appearance and
When using physical appearance as bull selection criteria, one of the first things to evaluate is structural correctness. Without structural correctness, a bull will not perform nor last as long as expected. A bull should have a well-structured shoulder with his front legs at a right angle (90 degrees) from an imaginary line drawn from the top of the shoulder through the point ofthe shoulder to the elbow. You want a 120-degree angle from the elbow through the back of the pastern with the front hooves slightly turned outward about 20 degrees. On a structurally sound bull, the two front legs are parallel to each other.
Hindquarter structural correctness includes a slight slope from the hooks to the pins with an imaginary vertical line from the hook through the stifle. A right angle should exist from the hook through the pins to the stifle and a 120-degree angle from the stifle to the hock and down the pastern. Like the forequarters, the hind legs should be parallel and the hooves slightly turned outward about 20 degrees. If you don’t remember all these angles, watch the bull walk on a level surface. Structurally correct cattle will place each hind hoof in the track of the corresponding front hoof.
Bulls should look masculine and be thickest through the middle of their hindquarters when viewed from the rear. A strong, wide, flat back is an indicator of good muscling. Bulls with wide shoulders are not necessarily muscular, but circumference of the upper forearm is a good indicator of muscling.
Reproductive evaluation, which includes a breeding soundness examination, is used to help measure the potential sexual performance of a bull. Request results of a recent breeding soundness examination from the seller when buying a bull and conduct breeding soundness examinations on herd bulls annually before breeding season. If bulls cannot pass breeding soundness exams, cull them from the herd because they will not settle their share of the cows. It is best to have breeding soundness exams done by veterinarians.
“The basic breeding soundness exam consists of physical evaluation of the animal, examination of reproductive organs, measurement of scrotal size and evaluation of semen. Physical evaluations include structure, feet, eyes, mouth, gait and body condition,” said Clay Mathis of King Ranch Institute for Ranch Management. “Faults in conformation and injuries can result in the bull becoming lame soon after the breeding season begins. Structure soundness of feet and legs is of paramount importance if the bull is to travel and mount females in heat.”
“Poor vision makes a bull dangerous to handle and he usually is dominated by other bulls to the point his breeding effectiveness is reduced. Vision is an important factor in detecting cow riding activity, because they use it to find females in heat. Both eyes should have an absence of injuries, disease, cancer growths and pink eye scars. Examine older bulls for lost and severely worn teeth,” Mathis said.
“Lump jaw (Actinomycosis) is a chronic bone and soft tissue infection that is not responsive to treatment. Cull bulls with lump jaw as soon as it is detected. Body condition of 5 to 6 generally is recommended for range bulls entering the breeding season.”
“Following the physical evaluation, a complete rectal exam of vesicular glands, ampullae and prostate is conducted to determine if there is inflammation, adhesions or fibrosis. The penis and sheath are examined for any sores, lacerations, abscesses, scar tissue, hair rings, warts or adhesions. When erect, the penis should extend from the sheath in a straight line with the body of the bull,” Mathis said.
Scrotal size correlates well with daily sperm production and is a highly repeatable measure. On yearlings, scrotal circumference should exceed 34 centimeters. Bulls with larger testicles produce more semen, sire sons with larger testicles, generally reach puberty at an earlier age and sire earlier maturing heifers.
“If the bull scores satisfactory on the general physical exam and the complete exam of internal and external reproductive organs, a semen sample is collected and evaluated under a microscope for concentration, motility and morphology. Concentration, expressed as number of normal sperm cells present in each cubic centimeter of ejaculate, and volume, number of ccs of ejaculate, are important measurements in determining semen quality. Together, these values represent total sperm delivery which is an indicator of the bull’s serving capacity,” Mathis said.
Measuring motility of individual sperm cells is important for determining breeding soundness of bulls. Ideally, the ejaculate sample should contain more than 90 percent vigorous, progressively motile sperm cells. Morphology, or the shape of the sperm cells, is also an important semen characteristic. A small sample of semen is stained on a microscope slide and at least 100 cells are graded for normal shape. Sperm cells with droplets, bent or coiled tails, malformed heads or other defects are less apt to fertilize an egg.
“A bull can rank high in a breeding soundness exam, but if he lacks libido (sex drive), the animal will not have the ambition to settle a large number of cows. There is no practical way to estimate a bull’s potential mating ability except to observe him servicing cows,” Mathis said. “Assessment of libido and mating ability is important to help detect physical abnormalities that would prevent a bull with good semen from settling cows.”
Parentage, performance records and genetics
Performance evaluation of the individual, his progeny and relatives is also a basic herd sire selection criterion.
All meaningful performance records are adjusted for sex, calf age and dam age if there is maternal influence. It is important to compare bulls and females within contemporary groups. A contemporary group is cattle of the same breed composition and sex, similar in age and raised under the same management conditions. Cattle of a contemporary group have had an equal opportunity to perform. Performance records should account for genetic change due to selection and be comparable across herds and years. Traits included in performance records are shown in Table 2.
Expected progeny differences (EPD) and accuracy (ACC) values are refined forms of performance records. An EPD is the estimate of how future progeny are expected to perform in each of the traits listed in Table 2. It is expressed as either a plus or minus number and has an accuracy value that increases with additional records. As more records are added, the EPD is a more reliable predictor of the animal’s genetic potential. It is possible to calculate EPDs on animals that have not had progeny if they have relatives with an EPD. Performance records are submitted by individual seed stock producers to their respective breed associations who calculate EPDs.
Genetic markers are used to develop genomic enhanced EPDs (GE EPD).
Genes responsible for different traits have specific locations on chromosomes and these locations are known as markers.
There are a number of commercial markers available for color, carcass merit, pregnancy and various production traits.
Genomic enhanced EPDs combine all available information from genetic markers with EPDs to improve their accuracy, especially on young bulls with few or no progeny.
In summary, select bulls using EPDs to improve traits that are of economic value to your operation. Select bulls that have a good health program and have passed a breeding soundness examination. Remember that selection goals should be stationary targets. Do not continue selecting for traits unless you know they have economic value.