Diseases and Enviroment
Air Quality, Ventilation and Drafts
We take good air quality for granted. However, a rabbit kept in a hutch outdoors may suffer from drafts, if the insulation is not good enough. On the other hand, if they are not cleaned out often enough, or ventilated well enough, stale air results, and ammonia fumes can build up and damage their lungs. Either way, respiratory diseases can result. Bacterial infections of the lungs that would otherwise cause minor problems can be life threatening in such badly kept rabbits.
Rabbits need a reasonable air space, good ventilation, but no drafts, and regular cleaning, to keep them in optimum respiratory health. Remember that their noses are only a few inches above the floor, and so they are very vulnerable to a build up of dirty bedding, which we may not even smell from where we are.
For this reason, spacious quarters, for example a shed rather than a hutch, with a smaller, well insulated and regularly cleaned out area to go into in colder weather, are ideal.
Temperature and Humidity
If rabbits are provided with good bedding material, and protected from drafts, they cope well at relatively low temperatures. However, rabbits don't tolerate very high temperatures well, especially if combined with humid muggy weather. They can struggle to breathe, not being able to pant effectively, and can suffer heatstroke in the same way as a dog kept in a hot car. It is important to avoid placing rabbits in runs in direct sun, and indoor rabbits may benefit from air conditioning or at least a fan. Heatstroke can be life threatening, and, as above, survivors can suffer severe respiratory problems.
Without becoming obsessed with cleanliness (remember that these animals are evolved to digging, and living underground, and often feel more comfortable in an environment that smells familiar: excessive disinfection can make it difficult for the rabbit to feel relaxed, and such stress can be harmful in itself), it is important to ensure that the living areas are cleaned daily. A build up of ammonia fumes from urine can be damaging to the lungs and airways. A build up of faeces can allow diseases, including coccidiosis, to proliferate. And damp and dirty flooring can be a major cause of sore feet.
Substrate (Cage or Hutch flooring)
As I've suggested above, the surface that a rabbit stands on is the single most important factor in having healthy feet. Imagine wearing poorly fitting shoes 24 hours a day, 7 days a week, and you can appreciate that if the floor materials are dirty, rough, wet, or just not quite right for the rabbit, problems can develop quickly and become very serious. Often by the time a rabbit is seen to have a problem and taken to the vet, the damage has been done, with infection reaching deep into the feet, sometimes down to bone. In such cases, often nothing can be done, and the rabbit has to be put to sleep. Prevention is much better than cure: checking you rabbits feet regularly (get your vet to show you how to do this), and making sure that ample clean dry hay is provided as bedding, should help to prevent this problem.
As well as being more fun for the rabbit, having lots of space to move about in is physically good for them as well. Moving around improves the blood supply to the feet, and helps prevent them standing in one place, leading to foot problems. It helps to keep them fit: unfortunately, far too many pet rabbits are overweight, which produces a whole range of health problems, as with people. It exercises their muscles and bones, minimizing the risks of spinal disease, which is a common cause of suffering in rabbits that have been confined to small hutches. And its generally good for their hearts and lungs. Don't forget that rabbits like to stretch up, standing on their back legs, so give them enough height to do so, most hutches don't allow this. And remember that rabbits need to be able to reach their back ends to eat their caecotrophs (the squishy faeces that can often be mistaken for diarrhoea, but is actually the end of the first stage of rabbit digestion). This can be difficult in small, low hutches, and can lead to a build up of such material caking their bums. In the worst cases, this can attract flies and lead to maggots eating their flesh. This is one of the most awful things that I, as a vet, see every year, and in nearly every case it can be prevented. Many rabbits die from this, and those that don't require intensive treatment for several days to help them through it. Lack of physical movement can also cause problems with gut motility, which can lead to serious health problems.
LightThere is some evidence that regular exposure to sunlight is good for rabbits, producing vitamin D and helping them to use calcium in their diet effectively. This can help in preventing spinal and dental disease, and whilst a lot of house rabbits seem absolutely fine, hutch bound rabbits, who rarely see the light of day, have lower levels of vitamin D, and higher levels of such problems than those with access to a run.
While I think that rabbits that have regular exercise in fresh air and sunlight seem to be happier and healthier, it is important to keep them safe. Wild rabbits can bring diseases (Myxomatosis and Rabbit Viral Haemorrhagic Disease) into the garden, and dogs, foxes and cats can catch the unwary rabbit. Regular vaccination minimizes the risks of the former, and sturdy accommodation, with runs that cannot be dug out of or tipped over, helps keep bunnies safe from predators. Remember also that neutered female rabbits are less likely to dig their way out. Flyscreens, and careful use of fly repellant products reduce the danger of biting insects spreading myxomatosis, and from flies laying eggs on the rabbits skin.
If in doubt about any of these points raised here, or if you have any questions, do not hesitate to contact your veterinary surgeon for specific advice.