Quality bulls: Breeding soundness exams recommended
The impact of the bull on the genetic makeup of a herd is important, according to University of Nebraska Beef Extension Specialist Rick Rasby.
“He provides half of the genetic material of each calf. He services between 15 to 50 females annually and 80 to 90 percent of the genetic change in a herd is the result of the bulls selected,” he explained. “This is why it is important to make astute and well-planned selection of bulls.”
Unfortunately, too many producers pull the bull after breeding season and let him fend for himself. Although Rasby pointed out how important it is to have a veterinarian do a breeding soundness exam each spring before breeding season, M. Wayne Ayers, DVM with Caine Veterinary Teaching Center at the University of Idaho stated in his report Management of Bulls for Natural Service, that only 26.8 percent of respondents in a NAHMS 2007-2008 survey reported using a breeding soundness exam (BSE) on a regular basis.
“It would seem that most producers want delivery of a bull with the potential to be a satisfactory breeder, but once delivered, they assume nothing will change and the bull will remain fertile and a good breeder from thereafter,” Ayers wrote.
A breeding soundness exam (BSE) is necessary because the bull can become infertile permanently or temporarily at any time.
Scrotal damage can occur during the winter, Rasby said. Frostbite can impact the sperm produced and the capacity, he said. Ayers added that orchitis, epididymitis, vesiculitis, testicular degeneration, traumatic injuries to the penis or prepuce and limb injuries or arthritis can all impact sperm production.
“Some of these conditions are visible to the producer and therefore are treated or the bull is culled when detected,” he said. “However, most of the inflammatory conditions would only be detected if a thorough BSE were performed.”
If a bull can service an average of 25 cows each season, the bull represents an estimated $20,000 in gross income each year.
“It is the goal of most producers to get their cows bred, and to get them bred early in the breeding season,” Rasby said.
Producers should have their bulls examined early in the breeding season and make necessary preparations, he explained.
For bulls from 15 to 18 months of age to maturity, Rasby recommends working with a veterinarian to make sure vaccinations are up to date.
“If bulls are purchased from a seedstock producer, they should have current vaccinations and have passed a BSE,” he said.
Passing an exam
According to Ayers, a passing BSE consists of a physical exam of the feet and legs, eyes, vesicular glands, ampullae or prostrate, inguinal rings, penis and prepuce, testes and spermatic cord, epididymides, scrotum and any other physical abnormality that could prevent the bull from successfully breeding.
A veterinarian will also look for sperm mobility greater than 30 percent, sperm morphology greater than 70 percent, and a scrotal circumference that is age dependent, he added.
According to the Beef Improvement Federation, a 15- to 18-month-old bull should have a scrotal circumference of at least 31 centimeters.
“It is a threshold trait,” Rasby said. “As a producer, I like to see that a little higher. I select bulls with at least 33 to 34 centimeters. The scrotal circumference impacts sperm production, and the relationship between scrotal circumference to the daughter’s puberty has been well documented. As scrotal circumference increases, days to puberty decreases in the daughters.”
The bulls should also be in at least a body condition score of six going into the breeding season. Younger bulls that are in the 15- to 18-month range have been known to lose 100 pounds or more during the breeding season, Rasby said.
“It is important to have them in proper body condition because they are still growing. You don’t want them to lose muscle tissue and condition during the breeding season,” he said.
If the bulls have just been purchased, Rasby said it is important to get them home as soon as possible before the breeding season begins. If the bulls are over-conditioned, the producer should reduce energy-intake.
“Don’t starve them back to the body condition score you want them in,” Rasby cautioned. “They need to keep gaining, but at a slower rate.”
The bull battery should also be introduced to one another before the start of the breeding season, so they can establish a hierarchy.
“Introduce them in a pasture or a large open area,” he said.
For bulls that aren’t in a body condition score six, Rasby recommends starting to feed them 80 to 100 days before the start of breeding season.
“It allows them to build their energy reserves gradually,” he said.
If the bull wintered well, it may only need five to seven pounds of grain per head per day and some good quality hay. If the bulls are thin, they may need up to 20 pounds of grain per head per day and some good quality hay.
At the University of Nebraska, Rasby said the bulls graze on dormant native range and are supplemented with four to five pounds of distiller’s grain each day. He noted it is also important to allow 24 to 30 inches of bunk space for each bull.