Making a Teaser Bull 

D. E. Larsen, DVM

The large animal surgery rotation in veterinary school with Dr. Annes was much more enjoyable than the rotation with Dr. Adams.

Dr. Annes had a varied mix of species and was a great instructor.

“Today, we have a young bull to make into a teaser bull,” Dr. Annes said. “What do you know about teaser bulls, Larsen?”

“Not much, other than they are used to mark cows in heat for herds using artificial insemination,” I said. “So to keep them from impregnating the cows, we do a vasectomy on them.”

“That is close,” Dr. Annes said. “And a vasectomy is adequate in a small closed herd situation. But in larger herds, especially with any range exposure, we have to be concerned about the transmission of trichomoniasis. Trich is become a serious problem in many areas today and destroys fertility rates.”

“How do you prevent the teaser from copulating with the cows being marked?” I asked.

“There have been several methods attempted,” Dr. Annes said. “The problem becomes, how do prevent copulation and still have the teaser maintain adequate libido to do his job? Some of the early procedures caused enough pain on erection that the bulls were quick to give up on the job.”

“What kind of pain are you talking about?” I asked.

The first attempt was very simple,” Dr. Annes explained. “The thinking was the bull was only needed for the herd to give all the cows one attempt at AI. So, after one heat cycle, twenty-one days, all the cows should have cycled and been bred with AI. Then they would be turned in with the herd bulls, and the teaser could be salvaged. With that thinking, they would pierce the prepuce,  place a bolt across it, thus preventing the erection from being extended out of the prepuce. It could be done cheaply, and it seemed to work. The problem was it was so painful for the bull that he was not functional for the full twenty-one days.”

“We are back to square one,” I said. “My guess would be to cut it off and do a low heifer on the bull.”

“That’s a thought and might be something that would work, but it might be a bit drastic, and it reduces the salvage value,” Dr. Annes said. “We tried a tie-down procedure where we would place a couple of sutures at the level of the retractor penile muscles to anchor the sigmoid flexure and prevent the penis from extending beyond the prepuce. That worked better than the bolt, but it reduced libido within a couple of weeks.”

“Did they try any other procedures?” Jim, the junior student, asked.

“Some veterinarians have tried to androgenize a cow,” Dr. Annes said. “By injecting her with enough testosterone, you can change her behavior enough so she will do a pretty good job of heat detection. Not as good as an active young bull, but satisfactory in many cases.”

“So if we are going to operate on this young bull today, you must have a new procedure that solves all those problems,” I said.

“Yes, today we are going move the preputial opening over to his side,” Dr. Annes said. “That way, we eliminate the pain issue and allow pretty normal penile function. It just is in the wrong direction and misses the mark.”

“It still will leave the bull feeling that he is missing out on something,” I said.

“Yes, but these are young bulls, and they continue to work at it pretty hard through a couple of cycles,” Dr. Annes said.

“I guess there is no reason to do a vasectomy then,” Jim said. 

“I still recommend doing a vasectomy,” Dr. Annes said. “For a couple of reasons. If a veterinarian is out in the field doing this procedure, there is always a possibility that the placement site might not be lateral enough. That will allow penetration. And, in at least one case, the bull figured things out, changed his point of attack, and accomplished penetration consistently. You understand, the reproduction system was made to work.”

After the discussion, we brought the young bull into the surgery area. We sedated him with a small dose of Rompun.

Positioning him on his back, the belly was prepped. Dr. Annes drew an arc on his belly, from the prepuce to the point on the side of his belly where we were going to place the orifice.

We made a circular incision around the preputial orifice. We extended it down the midline so we could free up the prepuce. Then we tunneled under the skin to the new site where we would place the orifice. We removed a patch of skin to match the size of the preputial orifice we were moving. We placed a sterile glove over the end of the prepuce and pulled it through the tunnel with a length of umbilical tape.

We sutured the end of the prepuce in place at its new site, closed the incision on the midline, and at the site where the prepuce had been located.

“Now for the vasectomy,” Dr. Annes said. “There are a couple of ways to accomplish this; one is the standard approach through the cord, and that is fine. But in the field, especially if time is an issue, you can just clip the tail of the epididymis on each testicle. That is a lot quicker and accomplishes the same function.”

With a small incision through the scrotum, we expressed the tail of the epididymis into the incision and made a nick in the tunic. A portion of the tail of the epididymis was expressed out of the tunic and snipped off. A couple of sutures, and we were done with that side. The same thing on the other side took even less time.

“Okay, that is all there is to it,” Dr. Annes said. “Let’s wake this guy up, and he is good to go to work.”

“Do they still salvage these guys after one season?” I asked.

“I am finding that this procedure leaves the bull functional for several years,” Dr. Annes said. “How long remains to be seen since I have only been doing this procedure for a few years. And I am told that some drugs on the horizon will synchronize estrus in a herd and make the need for a teaser bull a thing of the past.”

“Until then, I would guess this is the best procedure out there,” I said.

“Until then, time marches on, and this profession is always changing,” Dr. Annes said.

Photo by Bulat Khamitov on Pexels.

Published by d.e.larsen.dvm

Country vet for over 40 years in Sweet Home Oregon. I graduated from Colorado State University in 1975. I practiced in Enumclaw Washington for a year and a half before moving to Sweet Home to start a practice.

2 thoughts on “Making a Teaser Bull 

  1. Thanks for a fascinating technical explanation of another oddity from the veterinary world. I was curious about the term “teaser bull”. I guess I knew that a teaser bull was handy for folks doing A.I. but I thought the greater value to herdsmen was to use the teaser bull to stimulate early estrus in the cows, probably via olfactory stimulation.

    Your thoughts?

    Liked by 1 person

    1. In my experience, the teaser bull was pretty much eliminated with the introduction of prostaglandins.
      Cows cycle on a regular basis, pretty much every 21 days. Changing that can be done with prostaglandins via injection or by the induction of prostaglandin release in the body, as illustrated in my story One More Pregnancy.
      Doing a quick google search, I see one article from 1995 that speaks of the psychosexual stimulation that the teaser bull provides. Pretty much hogwash in my view.
      Maybe teasing a mare might make her more receptive, but doesn’t affect her ovulation.
      There are reflex ovulators. Cats, Rabbits, and Ferrets all ovulate with the stimulation of coitus. Camels, llamas, and alpacas are induced ovulators probably from products in the seminal plasma.


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