Muscular and skeletal degeneration in rabbits
that lack
exercise
Kim Chilson
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Wild
rabbits are very athletic animals that are built to move rapidly in order to
find food, water, find or fight mates, or flee predators over greater
distances to find a hiding place. This daily exercise strengthens the
locomotive muscles, fortifies their heart and lungs and increases their
resistance against stress. Regular movement will fortify muscle and bones,
will stimulate the blood circulation, and the activity and functioning of
organs including the digestive system.
House rabbits often do not have the
possibility to develop as their wild brothers and sisters, as they are often
confined in small hutches or cages with poor possibilities to exercise their
muscles and develop strength. This will inevitably lead to systemic
hypoplasia underdevelopment of tissues or organs) and the development of
physiological, physical and/or behavioral disorders. Physical disorders include: ·
Overweight. The lack of exercise
needed to burn calories and a rich diet will undoubtedly lead to overweight
and accumulation of fat in female and male rabbits. This can lead to the
development of (ulcerative) pododermatitis, cardiovascular problems, and skin
problems, due to the inability to groom properly. Physiological disorders include: ·
Gastro-intestinal disorders, e.g.
decreased intestine motility, ·
Cardiovascular disorders, e.g. weak
heart muscle, ·
Urinary disorders, e.g. soiling of
the perianal region, paste-like consistence of urine (sludge) or formation of
kidney or bladder stones, ·
Pulmonary disorders, due to
cardiovascular problems.
Muscular and skeletal problems When a rabbit is not given
opportunities to exercise, the muscle mass will not develop and remain weak.
In terrible cases, a rabbit has been found unable to develop a proper motor
coordination and normal ambulation. The heart is also affected and will
remain weak. Aside problems of proper blood circulation and blood pressure, a
weak heart will lead to problems when a rabbit will face a stressful
situation. While a well-trained wild rabbit can cope with the stressful
event, like being chased or hunted and will flee over a greater distance to
find a shelter, the poorly exercised rabbit, that is confined in a cage, may
not be able to cope with the situation and may faint or die from a cardiac
arrest. Lack of exercise furthermore
influences the vertebral column. The spine possesses 3 types of muscles
connecting the transverse and spinous processes of
each vertebra: the transversospinalis muscles. The
function of these muscles is not well understood, but is believed to be
involved in local rotations of the vertebral column or initiate bending. The
fact that some transversospinalis muscles cross a
few intervetebral joints suggests a role in the
control of the vertebral position and the stability of the spine, fore- and
hind- limbs. The spine is furthermore connected to
an intricate system of trunk muscles: ·
extensors, which include the back and
gluteal muscles (muscles that form the buttocks.), allowing for instance hip
movement, ·
flexors, which allow the spine to
bend, to control the arch of the lumbar spine, or hip movement, ·
obliques, that stabilize the
spine.
The bone structure and density is
often affected in rabbits with lack of exercise and/or a diet deficient in
calcium, mineralization of bones is poor. Weakened bones and bones affected
by osteoporosis are easily injured or broken. The vertebras of the spine
provide support for the back. If this is accompanied by poorly developed transversospinalis spine muscles and trunk muscles, the
normal balance of the spinal structure and the biomechanics can be altered,
which can leads increasingly to degenerative processes. Deformations appear
that will prevent the development of a good locomotric
activity. Intrinsic muscle disbalance furthermore
leads to degenerative changes of the lumbar vertebrae and of the femoral head
have been observed in rabbits that lack exercise. They include: ·
hemivertebrae (abnormal birth defect in which the vertebra fails to
develop completely. As a result of the growth defect of the spine, a
wedge-shaped vertebra develops, and neighboring vertebrae expand or tilt to
fit the deformity) ·
spondylosis (a condition of the spine marked by stiffness of a
vertebral joint) ·
kyphosis (humplike curvature of the spine) ·
lordosis (abnormal, increased degree of forward curvature of any
part of the spine). The severity of the deformations is
shown to depend on the cage size. Rabbits suffering from weak muscles
and poorly mineralized bones and/or bone degeneration are at increased risk
of spine fracture when there is an inadequate support of the heavily muscled
hindquarters, walking on a slippery floor, or twisting of the lumbosacral junction when frightened or restrained.
Fracture is commonly observed at the level of the 7th (L7) lumbar
vertebra.
Treatment A radiography will confirm the injury or
fracture the degree of severity of the problem can be assessed. Each case
needs to be evaluated on an individual basis.
Acknowledgement Thanks are due to Dr B. Langhofer (The Scottsdale Veterinary
Clinic Scottsdale, AZ, USA), and to A. Carpenter for sharing their
pictures. Further information 1. Katherine E. Quesenberry, James W.
Carpenter, Peter Quesenberry Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery
Includes Sugar Gliders and Hedgehogs, Elsevier Health, 2004. 2. Frances Harcourt-Brown Textbook of
Rabbit Medicine, Oxford UK: Butterworth-Heinemann, 2001. 3. Paul Flecknell, editor, BSAVA
Manual of Rabbit Medicine and Surgery Gloucester, UK: British Small Animal
Veterinary Association, 2000. and references
therein. |
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