Horses are very fastidious eaters, taking great care over what they take into their mouths when grazing. Their mobile upper and lower lips are involved in sorting out what enters the mouth and they usually do a good job of avoiding unpalatable objects.
But occasionally foreign bodies are ingested, typically plant material such as blackthorn or rose twigs. These are usually eaten when the horse is grazing near a recently cut hedge, browsing directly on a hedgerow or when twigs are incorporated in hay/
As well as foreign bodies occurring in the oral cavity, they can be found in the nasal cavity, throat, windpipe or oesophagus, where they become stuck on their way down to the stomach.
A horse can accidentally inhale a twig through a nostril and it can become lodged in the nasal cavity pass on through to the throat or even go via the larynx and enter the windpipe.
Occasionally, twigs work their way down the windpipe and eventually end up in the smaller passages of the lungs themselves (the bronchi). In a similar way, a twig or bramble that has been eaten can become stuck in the mouth, or, as the horse attempts to swallow, it may become caught in the throat or oesophagus.
The difficulties caused by foreign bodies lodging in abnormal sites will vary in each case. If a twig is stuck in the mouth, the horse will have difficulty eating, there will be excess salivation and exaggerated chewing movements are often seen/
Nasal foreign bodies cause excessive snorting, a discharge and sometimes bleeding from the nostril.
If the trachea or a bronchus of a lung is the site at which the plant material becomes lodged, the signs shown are often more subtle. The horse may cough and have a discharge at the nostrils. Also, he may appear depressed from time to time when his temperature is raised.
Finding the cause of the problem is easy in some cases, for example, a twig stuck across the roof of the mouth, but a diagnosis can be less clear. An endoscopic examination is often necessary to spot foreign bodies in the throat or windpipe.
Removal is not always straightforward. Often, the twigs have thorns, which dig into the soft tissues of the affected area, making extraction potentially injurious to the tissue. Also, they may break when removed and there is a risk of a small part being left behind. Furthermore, the area where the material is stuck is often well supplied with blood vessels and likely to bleed, making foreign bodies difficult to find, especially if an endoscope is being used.
In humans, foreign bodies aspirated into the windpipe are a relatively common emergency. The type of objects range from peanuts or vegetables to pieces of a toy breathed in by small children. In these cases, a rapid anaesthetic allows the retrieval of the object, with the assistance of an endoscope.
By contrast, the removal of the equine foreign bodies varies from straightforward manual removal from the mouth or nasal passages, if close to the nostril, to a full anaesthetic and surgical procedure.
Manual removal can be carried out with the aid of a gag and with or without sedation depending on the horse’s temperament. The endoscope allows us to examine objects in the nose, throat or windpipe and sometimes they can be snared using grasping forceps passed down the endoscope. Other throat or oesophageal foreign bodies may require a general anaesthetic to enable them to be removed manually via the mouth.
The most recalcitrant foreign bodies in the windpipe may require a tracheotomy – i.e. surgery cutting down through the trachea to gain access to the plant material. Sometimes a surgical procedure is required to remove foreign bodies in the oesophagus.