Metabolic Bone Disease and Shell Pyramiding in Turtles and Tortoises

A healthy shell is more than a protective covering. It is part of a turtle's or tortoise's skeleton and depends on proper nutrition, calcium absorption and exposure to ultraviolet B (UVB) light. Two commonly encountered problems in captive chelonians are metabolic bone disease (MBD) and shell pyramiding. Both are associated with inappropriate husbandry and can have lasting consequences.

What is metabolic bone disease?

Metabolic bone disease is a condition in which bones become weak, soft or deformed because the body cannot maintain normal calcium and phosphorus metabolism. It is particularly common in growing turtles and tortoises.

The main causes include:

• Insufficient calcium in the diet.
• Excess phosphorus, which interferes with calcium balance.
• Inadequate UVB exposure, preventing normal vitamin D3 production.
• Incorrect temperatures that interfere with digestion and calcium absorption.
• Poor-quality or nutritionally unbalanced food.

Recognising the symptoms

MBD develops gradually, and visible symptoms may indicate that the condition has already progressed.

Watch for:

• A soft or unusually flexible shell.
• Swollen or deformed limbs.
• A soft or misshapen jaw.
• Difficulty walking or supporting body weight.
• Muscle tremors and weakness.
• Reduced appetite and slow growth.
• Fractures in advanced cases.

A shell that remains unusually soft beyond the early growth stage warrants veterinary examination.

What is shell pyramiding?

Pyramiding is a shell-growth abnormality in which individual scutes, the plates covering the upper shell, develop raised, pyramid-like peaks rather than growing relatively evenly.

It is frequently associated with poor nutrition, inappropriate growth rates, inadequate environmental conditions and unsuitable humidity. The precise causes are multifactorial and can differ between species.

Pyramiding should not automatically be treated as proof of calcium deficiency. A tortoise can develop pyramiding without having MBD.

Prevention and care

Prevention begins with appropriate husbandry.

1. Provide UVB lighting: Use a suitable reptile UVB lamp or safe access to natural sunlight. Ordinary glass windows block most useful UVB radiation.
2. Maintain a balanced diet: Feed species-appropriate food with adequate calcium and a suitable calcium-to-phosphorus balance.
3. Supplement appropriately: Calcium supplementation may be necessary, depending on the animal's diet and veterinary advice.
4. Maintain correct temperatures: Provide a species-appropriate temperature gradient, including a basking area.
5. Ensure hydration: Fresh water and appropriate opportunities for soaking are important.
6. Monitor shell development: Observe shell growth and body condition regularly.

Treatment

MBD requires veterinary attention. Treatment may involve correcting the diet and enclosure, calcium therapy, diagnostic blood tests and radiographs. Severe cases may require intensive supportive care.

Existing shell pyramiding generally cannot be reversed. However, correcting the underlying husbandry problems can help prevent further abnormal growth.

The takeaway: A properly balanced diet, appropriate UVB exposure and suitable environmental conditions are essential for healthy bone and shell development.

References

1. Merck Veterinary Manual – Nutritional, Metabolic and Endocrine Diseases of Reptiles.

Merck Veterinary Manual

1. VCA Animal Hospitals – Common Diseases of Tortoises.

VCA Animal Hospitals

1. Tree of Life Exotic Pet Medical Center – Pyramiding in Tortoises.

Tree of Life Exotic Pet Medical Center

Article content © S Vejay Anand. All rights reserved.