Reptiles_-_Nutrition_Spring_2025

Basics of Reptile Nutrition

• Leading cause of morbidity and mortality in reptiles.

• Veterinarians must take the lead in dietary management.

• Various dietary classifications:

  • Herbivores: Turtles, tortoises, many lizards.

  • Insectivores: Lizards, some turtles.

  • Carnivores: All snakes, crocodilians, many lizards, and turtles.

  • Omnivores: Turtles (e.g. red-eared sliders), lizards (e.g. bearded dragons).

Calcium Requirements

• Generally, a 2:1 ratio of calcium to phosphorus is beneficial for mammals.

• Young reptiles often choose calcium-rich sources in the wild.

  • Example: Crocodiles have a 6.7:1 calcium to phosphorus ratio.

  • Example: Tortoises demonstrate a 6.4:1 ratio.

Nutritional Considerations for Herbivores

• Herbivorous reptiles require complex diets; no single plant provides a balanced diet.

• Some plant materials may cause issues if fed frequently or in large amounts.

• They typically do not select balanced diets in captivity.

• Hindgut fermenters and microbial fermentation occurs in the large intestine, emphasizing the need for vegetable fiber.

• Critical vitamins include A and D, with a higher availability of calcium than phosphorus.

Recommended Herbivore Diets

• A variety of foods should be offered:

  • Dark leafy greens, vegetables, small amounts of fruits, flowers, alfalfa hay, and commercial diets.

  • Include vitamin/mineral supplements as needed.

  • For tortoises: 80% commercial pellets/grasses, 20% dark leafy greens, flowers, non-starchy vegetables.

  • For iguanas: 50% commercial pellets, 50% produce (dark leafy greens, leaves, flowers, non-starchy vegetables).

Feeding Techniques for Herbivores

• Finely chop food for juveniles and coarsely for adults to prevent preferential feeding and improve fiber digestibility.

• Soak pellets to enhance digestibility.

• Avoid high-starch food, and steer clear of toxic plants (e.g., rhododendron, oleander).

Food Content Analysis

Oxalates

• Some leafy greens have high oxalic acid content, which binds calcium and impedes absorption (e.g., parsley, spinach).

• Oxalate:Ca molar ratio greater than 2 is detrimental, resulting in non-utilizable calcium sources.

Good Sources of Calcium with Lower Oxalates

• Foods with Oxalate:Ca ratios less than 2 include:

  • Prickly pear, collards, swiss chard, brussels sprouts.

• Low calcium, high oxalate diets should be avoided, though occasional consumption is acceptable.

Goitrogens

• Found in the Brassica family: cabbage, kale, mustard greens; these may inhibit iodine uptake, potentially leading to hypothyroidism.

• Hypothyroidism is rare in reptiles.

Nutritional Considerations for Insectivores

• Important insects include spiders, worms, crustaceans; all insects must be nutrient-loaded prior to feeding.

• Insects commonly lack calcium and are multivitamin deficient.

• Dust insects with calcium-rich supplements to address deficiencies.

Carotenoids and Vitamin A

• Certain reptiles lack the enzyme necessary to convert beta carotene to Vitamin A, making it necessary for them to receive preformed Vitamin A in their diet.

• Carnivorous reptiles generally consume whole animals, while herbivores and omnivores are capable of converting carotenoids to Vitamin A.

Improving Calcium Content in Diets

• Gut loading of insects enhances their calcium content prior to feeding to reptiles.

• Dust insects with calcium supplements.

• Avoid feeding wild insects that might be toxic, like fireflies.

• Introduce a diverse insect diet while supplementing with vitamins once or twice a month.

Nutritional Considerations for Carnivores

• Carnivorous diets vary based on anatomic adaptations affecting prey selection.

• Generally, they do not require supplementation and need fresh, pre-killed prey.

• Avoid feeding rodents older than 6 months and fish older than 3 months.

• Tailor diet to typical feeding strategies based on the animal's ecology (arboreal, terrestrial, aquatic).

Feeding Guidelines for Snakes

• Prey should not exceed the girth of the snake.

• Ensure prey is defrosted and warmed before feeding; offer on a solid surface.

• Training to accept pre-killed prey is recommended.

• Discard or avoid food items frozen for over 12 weeks and those that might lead to obesity.

Feeding Frequency for Snakes

• Frequency based on caloric needs; juvenile snakes require feeding every 2 to 7 days, while adults may need it every 7 to 21 days.

Nutritional Considerations for Carnivorous Lizards

• Recommend offering lean rodents that are pre-killed.

• Supplements may not be necessary; however, immature rodents should be dusted with calcium to enhance intake.

• Avoid feeding commercial pet diets aimed at other animals (canine, feline).

Nutritional Considerations for Carnivorous Aquatic Turtles

• Pellets and gel diets should be utilized along with live food choices like earthworms, insects, and pinkies.

• Avoid marine fish in freshwater diets and be cautious with goldfish due to tuberculosis risk.

Omnivores - Box Turtles

• Feeding breakdown:

  • 50% insects, snails, earthworms, pinkies

  • 45% vegetables

  • 5% fruit

Omnivores - Bearded Dragons

• Diet should consist of 50% dark leafy greens and flowers (no fruits), dusted with calcium.

• Other 50% should include insects, with the occasional pinkie offered.