During an undergraduate livestock medicine class a few years ago, our class took a field trip to a dairy barn to help dehorn some young Guernsey calves, only 2-4 weeks old. I remember the excitement and trepidation of performing a cornual nerve block for the first time, using a lidocaine and xylazine mixture to lightly sedate the calves while also controlling the pain of debudding. We each removed a horn bud using an electric cauterizing dehorner, and then sprayed the site with an antiseptic aluminum spray. During a recent clinical skills class, we learned more about the different types of dehorning tools and reviewed skull anatomy so we could accurately place a cornual block.
Horns grow from a patch of specialized epithelium or skin, and so horn buds are easier to remove when they’re small, before much keratinized horn has developed. The veterinarian or trained farm hand can pretty easily scoop out the horn bud (plus a good margin of skin, 0.5 to 1 cm) and be fairly certain a horn won’t grow. (Goats, however, are more prone to developing scurs, which are partial horns that regrow following disbudding. That’s why it’s important to remove a large margin of “normal” skin surrounding the horn bud, to decrease the chances of missing some of that specialized epithelium!)
I was interested to learn that goats need to be disbudded within the first week of life, because their horns grow much more rapidly than calves’ horns do. Our professors also told us that because goat skulls contain less bone, their thinner craniums provide less protection from the heat of the dehorner. They told us how it wasn’t uncommon for a kid to have transient brain damage following disbudding. So as you can imagine, we second-years all made sure to practice using the dehorner for 20 seconds, then removing the dehorner for 20 seconds to allow the skull to cool down a bit.
As the animal ages and the horn continues to grow, the core of the horn calcifies and attaches to the skull. As you can imagine, it’s much more traumatic to remove calcified horn, because in order to remove the horn, you have to remove a portion of the animal’s skull, exposing the hollow sinuses to the air. The exposed sinuses take several months to heal, and controlling the flies drawn to the area is difficult.
Why do we dehorn livestock? Simply put, it’s because horns are dangerous to both people and animals. Horns are an excellent weapon, used in both defense and offense. Livestock use their horns to establish dominance within a herd. Our professors have said that they’ve seen even cattle with scurs do immense, even fatal, damage to other herd members. Handling dehorned cattle is also much safer for people. In my own experience, even dealing with reasonably well-mannered dairy goats is a tricky business, because you have to constantly be wary and have a back-up plan.