Pet Factsheets

Brachycephalic syndrome

A Miniature Lop
©British Rabbit Council

Brachycephalic means ‘shortened skull’. We commonly think of dog breeds when we think of brachycephalic animals with Pugs, British and French Bulldogs, Pekingese and Cavalier King Charles Spaniels being those which spring to mind, although there are many other dog breeds also classed as brachycephalic. However other species, such as cats and some rabbit breeds can also be affected.

Brachycephalic syndrome is a condition affecting short nosed animals which can lead to severe respiratory distress. Rabbits also suffer other health issues due to brachycephalic features.

Which breeds of rabbit are brachycephalic?

Look at a wild rabbit. Their skulls are elongated and slender – now look at a lot of the pet rabbit breeds that we see.

Breeds such as the Netherland dwarf, the lop-eared breeds (especially the mini, dwarf and French lops), and the Lionhead have been bred to have shorter, ‘cuter’ faces, becoming more and more brachycephalic in recent years; they have also become more popular choices as pets.

What is the problem?

These rabbits are their own downfall. They are ultimately cute and therefore appeal to people. Humans are drawn to rounded faces, and many of the brachycephalic rabbit breeds fall into this category. Sadly, there are lots of potential health and welfare problems for brachycephalic rabbits.

Many of these rabbits have a bottom jaw that is longer than the top jaw; when this happens, it causes dental malocclusion. This means the teeth don’t line up as nature intended. In dogs and cats this may cause issues chewing, some pain, or they may drop food, but the problem is not likely to be life-threatening.

For rabbits, the same is not true and it can become a life-threatening condition. Rabbit’s teeth (incisors and cheek teeth) are open-rooted and grow continuously throughout their life. The incisors grow at around 2-3mm per week and the cheek teeth approximately 2-3mm each month. Their teeth are worn down when the rabbit chews on abrasive foods such as grass and hay and adopts the correct chewing action to grind down all the planes of the teeth. If their teeth do not line up correctly no amount of chewing on any food is going to wear them down, so they will overgrow. Not only can this lead to the rabbit being unable to eat, but it can also cause painful ulcers and cuts to the cheeks and tongue. Rabbits can and do die from dental malocclusion. These rabbits often require frequent dental treatment which is likely to have to be performed under a general anaesthetic – placing strain on the rabbit’s heart and a serious financial commitment for the owner. Therefore, rabbits whose teeth do not line up properly are highly likely to suffer pain and have their welfare compromised both by the pain caused by the dental disease and the frequent treatment required. These rabbits can potentially need to undergo dental treatment every few weeks and they may then take several days or weeks to recover after each procedure.

The other issue is that being brachycephalic can affect the rabbit’s ability to breathe properly. Rabbits are obligate nasal breathers and mouth breathing is a sign of respiratory distress. Rabbits only breathe through their mouth when they can’t effectively breathe through their nose. This is often seen during episodes of heat stroke or when the rabbit is extremely stressed. Rabbits suffering from anything that blocks their nose, such as a respiratory infection with the associated nasal discharge, are at serious risk of this, but this is not exclusive to brachycephalic rabbits.

Rabbits with a shortened face have squashed noses and therefore have a reduced ability to cope with heat and stressful situations making mouth breathing, respiratory distress and potential death more likely, since they are unable to inhale sufficient oxygen to oxygenate the tissues through nasal breathing.

What about lop ears?

As well as the shortened faces, many of these rabbits also have lop ears. Nature intended rabbits to have ears that are upright for a variety of reasons. Upright ears can detect more sounds and at lower sound levels – important when you are a prey animal! Rabbits also use their ears to communicate with other rabbits – what position they are in gives other rabbits non-verbal cues as to whether the rabbit is happy, annoyed, relaxed, stressed or inquisitive. Rabbits with lop ears are mostly unable to perform any of these ear movements, potentially leading to behavioural and social problems.

Added to this, lop eared rabbits have a high level of middle ear infections. Ear-base abscesses, which are almost always observed in lop eared rabbits, often extend into the ear canal and inner ear structures, even though the rabbit can remain bright and seemingly happy in the early stages of the condition. They often require extensive surgery to attempt to relieve the infection.

What should I do?

Ideally, we need to stop breeding and buying rabbits that have abnormally shortened faces and those with lop ears. There are numerous breeds and crossbreeds of rabbits that don’t have these abnormal anatomical features and therefore are far less likely to suffer with the same or similar health and welfare conditions.

If you already have a rabbit who is brachycephalic you need to be aware of the potential problems they may face. Make sure they are fed a diet high in fibre – grass and hay must make up at least 80% of their diet, along with one tablespoon of pellets per kg of ideal body weight and a small pile of greens (not high sugar, eg fruit or carrot) each day, to try and ensure a healthy diet. Whilst this will not stop them suffering with congenital dental disease, it may increase the time they can go between requiring veterinary treatment for the dental disease.

Always ensure they have access to shade and an area they can remain cool, even if the weather does not seem overly warm.

Lop eared rabbits must have regular checks performed on their ears – you should feel the ear itself and down the side of the base of the ear for any lumps, which may indicate an abscess.

Make sure you insure your rabbits when they are young and before any health problems have been detected. Once it has it’s likely that it will be excluded from any insurance policy.

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