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Swimmers or Rickets in Juvenile Ferrets (Osteodystrophy)

Author: Michelle Brunton – Little Paws Ferret Rescue

Credits: Dr Kerida Stephanie Shook DrMedVet MRCVS and Dr Kirsty Suzanne Hosford BVSc MRCVS

In recent years rescues and vets have seen an increase in the presentation of Swimmers Syndrome or Rickets in young ferret kits. The medical term is Osteodystrophy.


What is Swimmers Syndrome?

Swimmers Syndrome or Rickets is a condition that affects bone development in young animals and is described as abnormal development and calcification of the bones. It causes bone pain, poor growth and soft, weak bones and in many cases, affected ferrets are unable to walk normally or show significant lameness due to pain. Kits with swimmers have a tendency to crawl on their stomach instead of walking on their legs, the legs may splay outwards giving the impression that they are swimming, hence the name. Their bones are brittle and can develop bone deformities and fractures from even the most innocent, everyday activities such as playing with litter mates or minor falls. The condition is mostly caused by a lack of calcium and other essential vitamins and nutrients that are found in a healthy ferret diet.


By six weeks of age a ferret kit should be walking confidently on their legs and should be active and playful. If a kit is lethargic and reluctant to walk then they could be ill.

Kit suffering from swimmers disease
Ferret Kit

What causes Swimmers Syndrome?

Juvenile ferrets (kits) are particularly susceptible to Swimmers Syndrome which is often caused by insufficiency of calcium in the diet either during the gestation period (pregnancy) or after birth or both.  Essentially neither the mother nor the kits were fed a diet with enough calcium, vitamin D and other essential minerals.

Many ferrets are given a diet consisting of all muscle meat, which can be deficient in calcium and high in phosphorous. Diets of only beef or chicken (or other muscle based foods) generally provide very little calcium which is required for healthy bone growth.

In pregnant jills (females) it is particularly important that they receive a calcium rich diet, as during pregnancy, the body needs extra calcium to help to form healthy kits. If adequate calcium is not received in the diet then it will be diverted from the jills own bones. This will weaken the jill and reduce the quality of her milk for the newborn kits. The jills milk may dry up and it is possible that she may kill the kits if they show signs of illness. A jill is also at high risk of infection, exhaustion and other illnesses when pregnant and nursing. If she is weakened by the loss of calcium then this can prove fatal for mum and kits.


Symptoms of Swimmers

  • Crawling along on their stomach (from 5 to 6 weeks a ferret kit should be walking upright on all four legs)

  • Ferrets are unable to walk or show significant lameness (sore legs)

  • Weakness and lethargy (ferret kits are energetic and excitable. Any ferret kit that sleeps a lot and shows little interest in playing needs to see a vet urgently)

  • Bending or deformity of the bones including rib cage, spine, and legs

  • Unusual movement when walking and running. Particularly a bunny hopping motion or limp.

  • Inability to close the jaw correctly (potential dislocation due to malformed joints)

  • Loss of appetite (Ferret kits are ferocious eaters and will fight and hiss at each other over food. A kit that is not interested in food should be seen by a vet)


What is a Healthy Ferret Diet?

Ferrets are obligate carnivores and their diet should consist of protein and fat which is obtained from a meat based diet. The ideal diet contains at least 32% protein and 20% fat with no more that 3% fibre. With animal based protein rather than plant based (such as cereals).

A good well-rounded diet is essential for all growing animals. There are several options from raw fed diet to commercial kibble based diet or a combination of both.

By 4 weeks of age, ferret kits have sharp baby teeth and are very adept at chewing. They are adapted to start eating meat at a very young age.

Raw Feeding - This can include shop bought meats such as:

  • Red meat - minced beef or pork, lamb, diced steak or leg meat, pig, ox or lamb heart

  • Poultry - Chicken, duck, turkey, pheasant, etc… including breast meat, carcass, legs, wings, neck, livers, heart

  • Game such as rabbit, squirrel, venison, etc…


Whole prey: For most ferrets, the best diet is one that consists of whole prey items. This is where ferrets are fed dead mice, chicks or rats. The benefits of this diet are the rich source of calcium from the prey’s bones, the vitamin-rich organs as well as the animal-based protein in the prey’s muscle. The disadvantage of this diet is often the stigma or distastefulness of feeding whole prey for owners, and the tendency of some ferrets to hide their food.


If 100% raw feeding then it is important to get the balance of meat, bone and offal right. The suggested ratio is 80% meat, 10% bone and 10% offal (liver, kidney, etc....) Heart is considered as a muscle meat so this can form part of the 80% meat. You can buy raw meat diet from commercial pet food manufacturers which is already scientifically mixed for you.

Commercial dry food: Kibble food is commonly used in the UK as it is convenient and easy to store. It needs to be high in protein and fat, designed specifically for ferrets. The first three ingredients (i.e. those occurring in the highest quantity in the diet) should all be meat products. Most cat biscuits are not suitable for ferrets.

Ferret kibble needs to be high quality such as Dr Johns Merlin, James Wellbeloved, Alpha Ferret Feast, Supreme Science Selective are all commonly used and recommended dry foods in the UK. Raw or cooked chicken, mince, rabbit, day old chicks, mice, an occasional egg yolk can offer variance and enhance the diet. 


What foods are not good for my ferret?

Dog food is not a suitable diet for ferrets. It is not high enough in protein and fat for your ferret. Dog food also contains vegetable protein and fibre which cannot be digested by ferrets, and can cause disease. Ferrets are carnivores and have a unique digestive structure which lacks many of the enzymes needed to enable the consumption of carbohydrates.


Cat food is not recommended for ferrets. Your ferret can eat kitten food, as it has a high meat protein content but cat food does not contain the same protein levels, so isn’t as beneficial for your ferret. Most cat and kitten foods contain a lot of grains, like rice which should not be part of a ferret diet. If a ferret is eating food with insufficient amounts of protein and fatty acids, he can suffer from malnutrition, dull coats, and other health problems.


Foods high in carbohydrates and fibres like fruit, Cereals, dairy products and vegetables should be avoided. Ferrets are lactose intolerant therefore milk, cheese, cream, yoghurt, etc… should be avoided.

These foods can have a negative effect on their digestive system and cause health problems. 


Swimmers is a serious disease affecting young ferrets and one that usually requires veterinary attention. An x-ray can be carried out to show the extent to which the bones are affected, identify and fractures and changes in the bone structure. This will help the vet to make a treatment plan. It is very important to assess the severity of any bone deformities and treat as soon as possible to facilitate normal bone growth.

Xray of ferret
Xray of ferret

In some cases the bone deformities seriously limit a good quality of life. They can prevent a ferret from walking normally, fractures to the limbs fail to reset or set in the wrong position, the bones can bend from the strain of the muscles pulling against them as they grow. A vet will help to establish chances of recovery with a good quality of life.

xray of ferret
Xray of ferret
Xray of ferret
Xray of ferret
Xray of ferret

In most cases swimmers has resulted from a diet lacking in calcium therefore this makes calcium supplementation a keys areas for treatment.

In the worse cases, some may never recover and may have to be euthanized to relieve suffering.




To make sure this never happens, if you are breeding, please make sure that your jill is fed a complete diet which is rich in calcium and prosperous from conception to weaning so that both mother and babies get all the necessary nutrients to keep them strong and healthy. Feed a good meat based diet with bone from around four weeks to at least 8 months. If you do not like to feed meat to your ferret then get an older one that is over a year and then feed a good quality kibble.

Occasionally swimmers syndrome can be caused by genetics. Silver ferrets are more prone to genetic abnormalities as many are born from inbreeding to achieve the colour. This causes damage to the genes resulting in abnormalities. If you have bred a ferret that has produced swimmers kits or any deformities then it is recommended that they are neutered or implanted and never used for breeding again.



Veterinary summary

The condition called rickets is caused by reduced vascularisation and mineralisation of the bone physis. The resulting pathological changes in the normal bone structure are most obvious in the metaphyses of the long bones. These changes manifest in a multitude of clinical signs including bone pain, a stiff gait, metaphyseal swelling, difficulty in rising, bowed limbs, and pathologic fractures. On radiographic examination, the width of the physes can be increased as well as distorted, and the bone may show decreased radiopacity. Advanced cases show angular limb deformity due to asynchronous bone growth. Kits display a reluctance to move or rise, ataxia, and hind limb lameness. The paws tend to be deviated when the kits stands. Clinical signs and disease progression becomes increasingly evident after 5-14 weeks. The kits are responsive but unwilling to move and play, rather assuming a sitting position or sternal recumbency. Pathological fractures may occur as a result of normal activity levels, causing sudden onset severe lameness. Long bones tend to be painful on palpation, and fractures of these bones as well as the vertebrae are common. Treatment of rickets is mainly dietary, correcting imbalances and calcium deficiency. Prognosis is fair when pathological fractures or irreversible bone damage has not yet occurred. Exposure to sunlight or UV light if housed indoors will help to produce Vitamin D precursors. Long term, affected animals may be prone to developing osteoarthritis where incongruent joint growth has occurred.


Veterinary summary prepared by Dr Kerida Stephanie Shook DrMedVet MRCVS and Dr Kirsty Suzanne Hosford BVSc MRCVS – Premier Vets, Low Fell, Gateshead, UK.

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