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You have most likely heard the term “gut loading” when it comes to your reptile’s feeders if you own an insectivorous or omnivorous species. Gut loading is when you provide the insects with food, with the intent of passing the nutrients on to your reptile after they consume the insect. If the feeders are not provided with a food or water source, they could resort to eating the cardboard or egg carton in the container with them, which would indirectly be ingested by your reptile or amphibian! The insects will also not survive for long without a source of hydration, forcing you to buy new feeders more frequently. By gut loading, you are avoiding your reptiles eating nutrient-deficient insects, and instead of giving them ample opportunity to gain their required nutrition.
Previous Methods of Gut Loading
It was previously believed that feeder insects could be gut loaded with bran, fish flakes, or a single vegetable or fruit such as carrots, cucumbers, or apples. Bran is enough to keep the feeder insects alive, but it lacks any additional benefits and contains acetic acid, which is calcium binding (ref. 1). Ideally, food that a reptile or amphibian consumes should have a calcium to phosphorous ratio of 2:1 (ref. 2) due to the important role of calcium in the vitamin D3 cycle. By gut loading with bran, this ratio becomes difficult to achieve. While fish flakes may seem like a better option since they could be high protein or have ingredients besides bran, they likely include other fillers or additives that may be unsafe or unnecessary for the captive reptile (e.g., many fish flakes contain dyes to give the flakes an appealing colour). The next assumption, providing a piece of a fruit or veggie, is certainly healthier for the reptile, but providing a single food source prevents the feeders from consuming a wide variety of nutrients (ref. 3). For example, while feeding strictly carrots to crickets will increase their beta-carotene content to help the reptile with the production of vitamin A, the crickets may not provide sufficient levels of other necessary vitamins and minerals. Rotating through different fruits and vegetables can eliminate this issue, but the selected foods should be assessed for their phosphorous content to assist in increasing the calcium level of the feeders as much as possible.
Where Did the 48 Hour Rule Come From?
It is important to note that most invertebrates do not store calcium in their body because they lack a skeleton. In crickets, calcium will remain in their gastrointestinal tract for approximately 48 hours. This time frame is where the idea of gut loading feeders 24 to 48 hours prior to feeding them to a reptile originated (ref. 3). Realistically, feeders should be offered food consistently to ensure they provide the reptile with nutrients besides calcium, such as carotenoids and other vitamins. To continue using crickets as an example, as the crickets grow, they will store vitamin E in their cell tissue (ref. 3), making them an excellent source of this vitamin. Vitamin E acts as an antioxidant and can help boost the reptile’s immune system (ref. 1).
The New Way to Gut Load
The current recommended method of gut loading is by either using a rotation of fresh vegetables, a high-quality commercial diet, or a rotation of both (ref. 3). As previously mentioned, carrots are a great source of vitamin A which is essential for maintaining good eye, skin, mouth, and muscle health (ref. 4). Since vitamin A is fat-soluble, it can be dangerous in high amounts. Some other beneficial vegetables to provide for feeders includes bell peppers, collard greens, and various types of squash. Preparing and rotating between vegetables for feeders may be intimidating for some keepers, so if you are a beginner or maybe don’t have the time to make salads for bugs, a high-quality commercial diet can also create nutritious feeders.
Things to Keep in Mind When Choosing a Commercial Gut Loading Diet
When choosing a gut loading formula, it is important to check the ingredients. Any commercial diets that are primarily made of bran should be avoided. The best formulas should contain ingredients such as alfalfa and a variety of plants and herbs (ref. 1). The next step to selecting a commercial gut loading diet is to check the calcium content. If the calcium content is too high in the formula, it is possible for the feeders to die as calcium is typically not palatable for them. If the calcium content is too low, then there is little benefit being passed on to your reptile. The ideal range for calcium within a gut loading formula is approximately 5 – 8% (ref. 2). One of the biggest advantages of a commercial gut loading diet is that the feeders cannot selectively choose what they are eating (ref. 3). For example, if you place both vegetable slice and a commercial diet in the feeders’ enclosure, the feeders will likely only consume the vegetable, missing out on additional vitamins from the formula. As such, if you decide to offer both fresh vegetables and a pre-prepared diet, only one of them should be given to the feeders at a time.
How to Provide Hydration to Feeders
Some commercial gut loading diets such as Repashy Bug Burger can be served to the feeders in a powder or gel form. Preparing the gut loading diets in a gel form will allow you to supply both a hydration and food source all in one. If you would prefer a dry or powdered formula, water can be given via gel water crystals (some of which are calcium fortified), a small, damp sponge, or by very lightly misting the feeders’ enclosure. Water bowls cannot be placed with feeders as they are at risk of drowning.
Don’t Forget to Dust!
In addition to gut loading, feeders should be dusted with a calcium or multivitamin powder before they are offered to the reptile or amphibian. Dusting feeders allows your reptile to receive additional calcium, and can boost selected vitamin levels. For example, Arcadia ShedSupport helps increase vitamin B levels to promote shedding and the growth of new scales. Calcium and vitamin powders are best used on a rotational schedule to ensure the animal receives a broad spectrum of vitamins and reduce the risk of overdose. A great suggested supplementation schedule based on the species of your reptile/amphibian can be found on the following website: https://www.arcadiareptile.com/earthpro/feeding-programme/
Conclusion
In the wild, “nutritional wisdom” encourages insects to seek out food that provides them with adequate vitamins and minerals, and consequently other animals will eat these insects (ref. 3). Our captive reptiles are not able to select which foods they will be eating, and neither do the feeders they consume. It is our responsibility as keepers to ensure that our animals are being provided with the best possible nutrition to allow them to live a long and healthy life.
References
1. Courtney-Smith, J. (2014). The Arcadia guide to reptile & amphibian nutrition. Arcadia Products PLC.
2. Reptiles and Research. (2022). Best Gut Loading Plan Using Modern Science [Video].
3. Reptiles and Research. (2022). The Art of High-Level Gut Loading, 9/10 Keepers Get
This Wrong! [Video]. Youtube. https://www.youtube.com/watch?v=aK-FOQ5tD84&t=2894s
4. Bjornebo, H. (2016, February 27). Diet supplements for reptiles. Arizona Exotic Animal Hospital. https://azeah.com/reptiles-amphibians-reptiles-amphibians-lizards-reptiles-amphibians-tortoises-turtles/diet#:~:text=Vitamin%20A%20is%20an%20important,vitamin%20A%20in%20their%20diets.