The Building of a Bull

By Becky Mills
Progressive Farmer Contributing Editor

When Robert Field puts one of his home-raised bulls on a customer's trailer, he wants to be absolutely sure that bull has what it takes to get cows pregnant.

"The worst thing that can happen is to sell a bull that doesn't do the job," said the Shuqualak, Miss., Brangus breeder. "That is every purebred breeder's worst nightmare. We offer a year's guarantee and if there is any doubt, that bull doesn't ever leave here."

Field's bull development and maintenance program directly affects his own cow/calf operation, Calyx Star Ranch. These home-bred bulls do all cleanup duties behind the producer's own AI (artificial insemination) breeding program for a 221-head cow and heifer herd.

The building of a Calyx bull starts when these potential herd sires are still with their dams. First, a seven-way blackleg vaccination when calves are 3 to 5 months old. At around 4 months of age, creep feeders are moved into pastures so calves learn to eat grain out of a trough. At weaning, they are separated from their dams and weighed. Field doesn't see this as a time to add any more stress to their lives, so this is all that happens for a week to 10 days, as the calves recover from the shock of weaning.

A round of vaccinations and deworming with a pour-on ivermectin follow. Vaccinations include a second blackleg and a modified live vaccine, Pyramid 4, which protects against bovine viral diarrhea (BVD), infectious bovine rhinotracheitis (IBR), parainfluenza-3 (PI3) and bovine respiratory syncytial virus (BRSV). In a month, he will repeat this vaccination.

From weaning until the time these calves are yearlings, Field hand feeds them. They get a grain ration once a day, and on Mondays, Wednesdays and Fridays, he gives them a second feeding. The goal of all this attention is to fine tune these bulls' weight gains, which he rechecks every two months.

"I want my yearlings to each weigh between 1,000 and 1,100 pounds," Field said. "I don't push them that much. I try to mimic the real world."

When Field takes those official yearling weights, he also vaccinates with Vira Shield 6+VL5, which guards against vibrio and lepto. He deworms them again at this point. In five to six weeks, he repeats the process.

WHOLE HERD HEALTH

Field's attention to detail hits the right notes, said veterinarian S.B. Bounds. The doctor stressed the importance of vaccination programs against vibrio and lepto.

"Bulls with vibrio can devastate a herd," he said. "They transfer it during breeding, and it can cause early fetal death." The Macon, Miss., veterinarian adds lepto can cause abortions at 6 to 9 months. He said it hasn't been a problem in his area for quite some time, but as it doesn't add significantly to the cost of the vaccines, he recommends including it as a matter of course.

Field's young bulls are ear-notched to test for persistently infected bovine viral diarrhea (PI BVD) and blood sampled for Johne's Disease, even though Calyx Star Ranch is certified Johne's-free.

"Dr. Bounds uses young bulls as a sentinel for the rest of the herd," Field said of his veterinarian. He explained they still test all cows 5 years old and older for Johne's, as this has been the age at which the disease usually shows up in the ELISA (Enzyme Linked Immunosorbent Assay) test. This is a blood test that looks for antibodies that would be produced by an infected animal.

ONE MORE LOOK

A month before sale time, all bulls, including those Field will use in his own herd, go through the final hurdle -- a thorough Breeding Soundness Exam (BSE) performed by Bounds. First is a physical exam, paying particular attention to a bull's feet, legs and eyes.

"If they have had an injury and lost sight in one eye, they can still pass," he remarked. "But we cull them for bad feet. They need to be able to get out and do the job."

Next is a three-part reproductive exam. Bounds starts with a scrotal circumference measurement on mature bulls, repeating the yearling measurement that Field has already done (see "The Measure of a Yearling").

University of Georgia (UGA) veterinarian Lee Jones said the idea of having that yearling measurement and then comparing it to where the bull is at by 18 months of age is a good practice. "We compare scrotal circumference as part of a BSE from year to year in herd bulls," he said. "The goal here is that we want to see if there has been any significant change."

Jones said when the scrotal circumference measurement is done, he will palpate testicles and epididymis, checking for any abnormalities. Bounds follows the same procedure at his check, including a rectal palpation to examine the prostate and seminal vesicles.

"We look for scrotal hernias or an enlarged prostate," he explained. He added it is not unusual to find infection in the seminal vesicles of young bulls, a condition treated with antibiotics.

Taking a semen sample is also standard in a BSE. Examined under the microscope, it is a way to measure mass and individual motility (motion) of sperm, as well as morphology (structure).

If a bull passes all parts of the BSE, Bounds labels him a satisfactory potential breeder (SPB). If he doesn't pass the motility or morphology section regarding the semen, that bull will be tested again in a month.

TIME AND CONDITION

After every box has been checked, and a young bull is ready to leave the ranch, Field asks his customers to continue to supplement the animal, keeping him at a Body Condition Score (BCS) of 6, and making sure not to overwork him.

He doesn't sell yearling bulls for fear they will be overworked. By the time a bull is 18 months of age, the cattleman is confident he is ready to do the job.

"With an 18-month-old, we know we can turn him in with 20 cows or heifers, but not over 25. Every year, we'll add five cows, but we don't go over 35. Then after they turn 5, we'll take away five cows a year.

"The BSE verifies that the bull can produce viable semen, but it does not ensure he will service cows or that he can successfully mount cows. It is best to observe him in the act. Also, watch for too many cows returning to estrus in around three weeks."

He keeps a watch on his own females, adding: "There is such a tight window to get a cow bred. If she gets bred early in the breeding season, that gives her more time to recover after she calves and before she is bred again. And those early calves weigh more at weaning."

THE MEASURE OF A YEARLING

At the same time he takes yearling weights and vaccinates bulls, Robert Field uses ultrasounds of potential herd sires to evaluate carcass characteristics. He does not emphasize one trait over another but is interested in a balance of masculine and feminine traits. He closely watches rib-eye area (REA) and intramuscular fat (IMF).

"To me, if the REA is larger and the IMF lower, that implies a more masculine individual, as muscling is a masculine trait," he explained. "More IMP, more fat thickness, implies a more feminine animal as fat is a feminine trait. A balance between the two is a plus since a bull sires both bulls and heifers," he added.

Field also takes scrotal circumference measurements on yearlings. If the young bulls measure under 30 centimeters, they are culled. He says they usually average 35 to 40 centimeters.

While scrotal circumference measurements are taken again later as part of his herds' Breeding Soundness Exam (BSE), Field believes the earlier assessment is a good economic move. By culling bulls at a year, he saves feed he would otherwise be giving a bull with a substandard measurement.

University of Georgia (UGA) veterinarian Lee Jones agrees with Field's emphasis. Measuring scrotal circumference is a vital part of the sale requirements for bulls going through either one of UGA's two central bull tests.

"The measurement is one of the three important parts of a thorough BSE of mature and yearling bulls," Jones said. "It is a crude estimate of the size of the testicles and the sperm-producing capacity. A yearling bull that has a small scrotal circumference at the BSE often has a very low sperm concentration."

Bulls that meet Field's requirements for scrotal circumference, yearling weight and ultrasound measurements are offered in one of Calyx Star's two annual bull sales. The October sale features spring-born bulls; the one in March is for fall-born bulls.

To find out more about Calyx Star Ranch or its bull sales, visit www.calyxstarranch.com.

(VM/CZ)

Copyright 2015 DTN/The Progressive Farmer. All rights reserved.