Friday again, another morning spent on the farm working with the dairy herd in diseases of ruminants. With Easter so close a lot of people have travelled home and so today’s group is really small. Last time was reproduction work so today is orthopaedics and other surgery unrelated to the reproductive tract including today dehorning.
Cows are generally gentle loving animals, however their heads are one of their primary weapons, and with horns they are actually quite formidable. This endangers workers, plus also the other animals in the herd. Most of time the tissue that grows the horn is removed when they are calves so that the horns do not grow, however if there is a problem with this then the horn can still grow.
These horns are basically made keratin which is the same as your finger nails – however in cows after they reach about 2 months the horn “bud” attaches to the skull underneath and the sinus cavity inside the skull will expand into the horn as it grows. This is where the photo is from – it is the hole that is left after the horn has been removed looking into the frontal sinus.
The horn has a nerve going to it (the cornual nerve) which goes from behind the eye so before we do anything this is blocked by using procaine as a local anaesthesia which means that there is no feeling anywhere around the horn.
After the horn bud attaches to the skull at around 8 weeks only a vet is allowed to remove it – farmers can only remove the tip of the horn so that it is not sharp. Removing the tip however doesn’t remove the danger as it can cause significant bruising and damage to others. So at this stage it is still beneficial to remove the horn, this is done by a surgical wire saw and usually takes under a minute to do (the record here is apparently 17 seconds). Once the horn is removed any bleeding from the blood vessels is controlled by ligation and antibiotic spray applied to the site.
Unfortunately this is the only way to remove the horn, and there is not enough loose skin in this area to close over this so it is left open. It takes around 4 weeks for a scab to form over this opening – and then a further few weeks for it to form a proper scar.
This does not cause as many side effects as may be expected – having a patch over the hole with a bandage is generally not liked by cows and they tend to remove it within hours. And from the studies I have read having a patch does not reduce the healing time. The only recommendation here is to keep the cows that have been dehorned separate to the rest – this is good from a management point of view as it is easier to check that nothing is going on with them.
The rest of the morning went do checking on some patients post digit amputation. One of these had a large abscess higher up the leg which was removed. This lead to some bleeding and I was allowed to ligate the bleeding vessels here. Today was my first suturing ruminants and it was pretty different for me with how thick and tough the skin is so I was pleased to get the practice. However even after ligation of the main bleeding vessels there was still significant capillary bleeding and so we applied a tourniquet to the leg to reduce the blood flow and allow clot formation before we released the cow back to the herd.
We were pretty disgusting when we finished, however went straight into lectures for contagious disease… The joys of vet school.