Vitamin A is important for the maintenance of vision (especially in dim light), growth and development, repairing of damaged tissues, new cell growth and cell differentiation, the immune function and is important for the proper functioning of the eyes, skin, mucus membranes and ducts.
Herbivores: Hypovitaminosis A is a commonly seen problem in chelonians such as box turtles, young red eared terrapins and other chelonians.
As vitamin A plays such a key role in the maintenance of the mucus membranes a deficiency will show immediate changes. The mucus membranes will harden and thicken causing the salivary and mucus glands to block up. This causes the oral and respiratory secretions to dry and cellular debris to build up because of poor functioning of the ciliary mechanisms whose role is in the removal of foreign particles from the airways. Swelling of the eyelids is also commonly observed along with the development of a condition known as xerophthalmia (dry eyes), as displayed in the picture above. A "parrot beak" and/or oral abscesses may also be indications of a diet lacking in vitamin A or beta-carotene. Other symptoms may include a runny nose, wheezing, raw infected skin, thickening of the horny layers of the skin, oedema (the swelling of the limbs due to fluid accumulation because of liver failure), and loss of appetite and weight.
It's role in the maintenance of the immune system means a deficiency makes respiratory and digestive tract infections more common. The most frequently seen example is pneumonia as seen in red eared terrapins which adopt a lop-sided position when swimming due to lung collapse or congestion which reduces buoyancy on the effected side. Upper respiratory tract infections are also common in tortoises suffering from hypovitaminosis A.
Toxicities are rare and are typically caused by over-supplementation or rarely through veterinarian error when excessively high concentrations of vitamin A are administered via injection. Acute toxicity develops with clinical signs appearing as dermal burns caused by dry skin that sloughs off leaving red raw patches, abnormal bone development and liver enlargement. Frequently death occurs within 24- 48 hours.
Appropriate oral supplementation of vitamin A or Beta-carotene is recommended along with the inclusion of foods containing vitamin A or beta-carotene within the animals diet. (N.B.- Beta-carotene is the main safe dietary source of vitamin A).
Injections with highly concentrated vitamin A are an option but are not recommended. Supplements given orally are absorbed much slower into the system than if they were injected allowing for a safer and more controlled rate of absorption. Animals suffering with dermal burns due to hypervitaminosis A should be given burn wound therapy, antibiotics and open wounds addressed.
Vitamin A is found in dark green and yellow vegetables and yellow fruits, such as watercress, swiss chard, turnip greens, carrots, squash (butternut squash), sweet potatoes, pumpkin, cantaloupe, and apricots, and for non-herbivorous species vitamin A can be obtained from animal sources such as liver and whole eggs.
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