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Supplementing insect feeders for frogs

Why supplement?

Most captive insectivores, such as dart frogs, are fed insects that are raised either commercially or by the keeper. Supplementing these prey items is both necessary and misunderstood; this article aims to explain both points, and to recommend research-based protocols and products for supplementation.

The recommendations here are intended only for dart frogs (though the needs of many insectivorous herptiles are quite similar, and so much here will be applicable to other taxa) that can be fed supplemented prey — so not, for example, new frog metamorphs that cannot or do not accept fruit flies. Frogs that are actively breeding may have different nutritional needs motivated by regular egg production; these needs are not addressed here.

The importance of calcium

Keepers sometimes assume that calcium must be provided because insects do not contain enough calcium for frogs. This is only partially correct, and is a misleading understanding. Though many feeder insects are calcium deficient, all contain much more phosphorus than calcium, and this imbalance is what causes health problems.

When a captive animal’s diet contains too much phosphorus in relation to calcium, parathyroid hormone (PTH) is secreted to reestablish proper levels. PTH causes a removal of calcium, first from blood plasma, then from bone — ‘nutritional secondary hyperparathyroidism’. (7) This removal of calcium leads to a failure of bones to properly form and eventually a degradation of existing bone — ‘metabolic bone disease’ (MBD).

Supplementing commercially produced feeder insects is necessary to correct the inverse calcium to phosphorus ratio of those insects (1,3,5), ideally targeting 1.5/1 Ca/P (9). Only certain calcium compounds are suitable for use as supplements, as the amount of elemental calcium delivered has to be sufficient to offset the amount of P in feeder insects. The Ca content of various possible calcium sources per gram of compound are (3):

  • Calcium carbonate: 400mg
  • citrate 211mg
  • lactate 130mg
  • gluconate 93mg
  • glubionate 66mg

Calcium carbonate is the standard for supplementation; calcium citrate can also yield acceptable results (3).

Failing to offer supplements at every feeding, often motivated by a hesitancy to “overdose”, is thus ill-advised. At least in regards to calcium, the overall dose is not so important as is offsetting the high levels of phosphorus.

Vitamin D3 is necessary

Vitamin D3 is required for proper uptake of calcium, and so needs to be provided. Though at least some species of dart frogs can synthesize Vitamin D through UVB exposure, all species also use dietary D3 very effectively. The simplest, least expensive and least potentially harmful way to provide Vitamin D3 to dart frogs is through supplementation. The risk of overdosing Vitamin D through supplementation is less than many keepers assume; though the daily requirements of amphibians are not well known, for most animals the presumed safe dose is 4 - 10 times the minimum requirement (3). Thus, an acceptable supplement product will contain Vitamin D3.

Preformed vitamin A is necessary

Vitamin A is also deficient in commercial feeder insects (2) Hypovitaminosis A is common in dart frogs, and is a cause of short tongue syndrome (STS) and pathologies of the eyes and reproductive organs (2), and general lack of immune response that can predispose the frog to infectious disease (3).

There is a misconception among keepers of many species of amphibians and reptiles that preformed Vitamin A (retinol A) is an overdose danger and should be replaced in the diet by previtamin A (carotenoids). This belief stems from a decades-old misinterpretation of chelonian respiratory issues as Vitamin A deficiency (most cases were due to Mycoplasmosis) that was treated by aggressive Vitamin A therapy (often via injection) (3). This practice led to widespread hypervitaminosis A, which in turn spurred a false assumption that preformed A is dangerous.

In fact, hypervitaminosis A is uncommon in captive herptiles, and the few cases that occur are typically due to the use of injectable A or the excessive feeding of mammalian liver (3).

Providing Vitamin A in the form of carotenoids was a response to the mistaken overdose worry. Some animals — herbivores and omnivores, primarily (8) — can convert carotenes to Vitamin A, and for these animals carotenoids may be a good source of Vitamin A. There is substantial evidence, though, that frogs cannot metabolize previtamin A (carotenoids) to Vitamin A (2, 3, 9). Providing frogs only carotenoids as a Vitamin A source is documented to lead to conjunctival (eye) lesions (3) and anecdotally the practice leads to death of the frogs, likely through inability to catch prey (12). Therefore, retinol A (performed Vitamin A) should be provided as a Vitamin A source. Carotenes have other benefits for frogs, though, and can be included in the diet in modest amounts (11).

B complex Vitamins are (probably) necessary

The B complex vitamins play a role in frog health, as well. Nerve issues, scoliosis, and spindly leg syndrome (SLS) have been associated with Vitamin B deficiency (9). Though feeder insects are not typically deficient in the B vitamins (4), an ideal supplement might include B vitamins.

How often to supplement

Supplementation protocols are thus best thought of as primarily correcting deficiencies in the food source, rather than providing vitamins and minerals to the frogs (about which vitamin and mineral intake needs are not well established (3, 4)). This is especially the case for calcium, which offsets the excess amount of phosphorus in feeder insects. Also, the vitamin content levels of every currently available all-in-one supplements are designed to meet the target animals’ needs when applied to all prey items offered. As such, every prey item should be supplemented at every feeding.

Which supplements are useful?

A satisfactory supplement dust must:

  • rectify the Ca/P ratio of insects
  • contain adequate Vitamin D3 for Ca metabolism
  • contain Vitamin A as retinol (preformed Vitamin A)
  • contain a wide range of other vitamins including E and the B complex
  • optionally contain other dietary supplements for which benefits have been established (e.g. carotenoids)
There are scores of supplements available, and nearly all of them are not suitable for dart frogs. Supplements most commonly marketed to frog keepers include:

  • ZooMed Reptivite with D3

Though this supplement meets all the other needs of frogs, since its primary ingredient is calcium phosphate it does not rectify the Ca/P ratio of feeder insects and is not suitable for use with dart frogs

  • Sticky Tongue Farms Miner-all and Vit - all


These two products are designed to be used together by gutloading prey with Vit - All, and dusting same prey with Miner - All. Beyond the tedious procedure recommended, the Sticky Tongue Farms supplements do not contain preformed Vitamin A and are not suitable for use with dart frogs.

  • Flukers Reptile Vitamin

The main calcium source in Fluker’s Reptile Vitamin is calcium phosphate, and for this reason is not suitable for use with dart frogs.

  • RepCal Herptivite and Calcium with D3

These are two separate supplements that are designed to be mixed immediately before use. Aside from the disadvantage of the tedious premixing procedure (necessary since RepCal does not use microencapsulated vitamins), RepCal products do not contain preformed Vitamin A and are not suitable for use with dart frogs.

  • Birkhahn A-Vital

I could find no direct manufacturer information on Birkhahn A-Vital. The first five ingredients (translated from German by Google) according to a retailer’s listings/product label are:

Stärke = starch (a filler)
Tricalciumphosphat = Calcium phosphate
Gelatine = gelatine
Mannit = mannitol (a sugar substitute with poor intestinal absorption; probably used here as a filler or flavor enhancer) Mannitol - Wikipedia
Tricalciumcitrat = calcium citrate

Though Birkhahn A-Vital contains all the major and minor vitamins of importance (though with a very elevated Vitamin A level, it is worth noting), it uses only unsuitable calcium sources (a common feature of many “legacy” supplements; Birkhahn A-Vital was formulated in the early 1990s) . Calcium phosphate cannot correct Ca/P ratios of insects because of its phosphate level, nor can calcium citrate as it contains insufficient amounts of Ca (3). For this reason, Birkhahn A-Vital is is not suitable for use with dart frogs.

  • Ranarium Cal Bee + D3
Cal-Bee + D3 | Ranarium

Though Cal Bee + D3 does contain a useful form of Ca (calcium carbonate) and Vitamin D3 neceesary for uptake of that Ca, it contains no further vitamins such as Vitamin A or E. It does contain a large amount (20%) of bee pollen. Bee pollen is a source of B-complex vitamins (though a highly variable source Dried bee pollen: B complex vitamins, physicochemical and botanical composition) (Chemical composition and botanical evaluation of dried bee pollen pellets)

I could find no studies whatsoever on the effects or value of bee pollen in amphibian diets.

Cal Bee + D3 is not a complete supplement for dart frogs, and contains an ingredient of questionable utility.

  • Various liquid ‘Calcium spray’ products (e.g. Fluker’s, Zilla)

Calcium spray products contain insufficient levels of calcium because they use unsuitable calcium sources (for example, calcium gluconate in Zilla’s product) or are simply mostly water (Fluker’s contains 6% calcium, compared to Repashy Calcium Plus 17%), and do not contain Vitamin D3, so Ca will not be absorbed by the animal. No spray products provide all the vitamins and minerals needed in a complete supplement. Calcium spray products are not suitable for use with dart frogs.

  • Ranarium Rana-Vit

Rana-Vit contains a useful form of Ca, as well as Vitamin D3 and retinol. The inclusion of bee pollen is likely intended as a source of B Vitamins; as mentioned, this is a highly variable source. Rana Vit includes a small amount (0.6%) of Maca root, a human food source that is sometimes used as a libido and sexual performance stimulant. I could find no studies whatsoever on the effects or value of Maca root in amphibian diets.

Aside from the mentioned ingredients of questionable value, Rana Vit is suitable for use with dart frogs.

  • Dendrocare

Dendrocare contains a suitable source of calcium, and all the major and minor vitamins needed for dart frog health. It does not contain any carotenoids, though some keepers may choose to supplement carotenoids separately. Dendrocare is suitable for use with dart frogs.

  • Repashy Calcium Plus

Repashy Calcium Plus is the current gold standard for dart frog supplements. It includes the proper form of calcium, all the major and minor vitamins, preformed Vitamin A and a range of carotenoids. Repashy Calcium Plus is suitable for use with dart frogs, and should be the first choice for an all in one supplement.


How to dust with supplement

Dusting feeders with supplement is simple. Place a small amount of the supplement dust in a cup or plastic bag. Add the feeder insects and swirl (if a cup) or hold shut and shake (if a bag) until all the insects are fully coated with supplement. Pour off the insects and offer to the frogs; discard the excess dust that remains in the cup or bag.

Though supplement dust adheres to insects for a handful of hours — at least five (10) — too many insects in the enclosure can be stressful to frogs. Feeding only as many as will be consumed by the end of the day is advisable. Remember that every insect offered should be dusted at every feeding.


An aside on gutloading

Some keepers attempt to “gutload” feeder insects as a substitute for dusting. To be a substitute for dusting, gutloading must:


  • rectify the Ca/P ratio of insects
  • contain adequate Vitamin D3 for Ca metabolism
  • contain Vitamin A as retinol (preformed Vitamin A)
  • contain a wide range of other vitamins including E and the B complex
  • optionally contain other dietary supplements for which benefits have been established (e.g. carotenoids)

What to use as a gutload

Over time, the common conception of ‘gutloading’ has lost its original meaning and come to mean simply offering food to insects before feeding them to the target animal (3). This practice does not accomplish any of the five supplementation goals listed above.

Contrary to much internet misinformation, very few diets are suitable for use as a gutload. No moist diets tested improved the calcium content of insects (5). Calcium enriched water crystals do not improve the calcium content of insects (4). Fresh fruits and vegetables do not contain sufficient calcium, nor usable Vitamin A, nor Vitamin D3 and so are not suitable as gutload diets; in fact offering moist foods along with a proper gutload diet actually reduces the effectiveness of the gutload procedure (1), as the digestive tract of the insects must fill only with calcium rich dry food for gutloading to be effective.

Research has shown that gutload diets with irregular particle size (0.5mm - 3mm) do not improve the calcium content of insects regardless of the calcium content of the diet (6). It is unlikely that homemade from scratch diets would meet the homogeneity requirements of an effective gutload diet, regardless of their vitamin and mineral content.

Furthermore, very few commercial products sold as gutload diets actually work, both due to poor manufacturing standards (particle size) as well as significant content deviations from labeled guarantees. In a test of five such products (Timberline Cricket Power Food, Fluker’s High Calcium Cricket Feed, ESU Reptile Gutload, JurassiDiet Gutload, and T-Rex Calcium Plus Food For Crickets) only one (T-Rex) improved the vitamin and mineral profile of feeder insects sufficiently (6).

Even using a suitable product, gutloading is only effective if the proper diet is fed to feeder insects for 48 hours before offering the prey (1). Clearly, gutloading is not at all a straightforward substitute for dusting, and is in almost every case unknowingly used improperly, and thus ineffectively.

Summary

  • All feeder insects offered to frogs need to be supplemented at every feeding.
  • Only Repashy Calcium Plus or Dendrocare are fully effective supplements dusts.
  • Gutloading is a very difficult, and almost always ineffective, substitute for dusting.




References, and for further study

1) Allen and Oftedal, 1989, “Dietary Manipulation of the Calcium Content of Feed Crickets” Journal of Zoo and Wildlife Medicine, 20 (1). (PDF) Dietary Manipulation of the Calcium Content of Feed Crickets

2) Clugston and Blainer, 2014 “Vitamin A (Retinoid) Metabolism and Actions: What We Know and What We Need to Know About Amphibians” Zoo Biology, 33(6). Vitamin A (Retinoid) Metabolism and Actions: What We Know and What We Need to Know About Amphibians

3) Divers and Stahl, eds. Mader’s Reptile and Amphibian Medicine and Surgery, 3rd. ed. 2019 Mader's Reptile and Amphibian Medicine and Surgery | ScienceDirect

4) Ferrie, et al. 2015. “Nutrition and Health in Amphibian Husbandry” Nutrition and Health in Amphibian Husbandry

5) Finke, et al, 2004, “Evaluation of Various Calcium-fortified High Moisture Commercial Products for Improving the Calcium Content of Crickets, Acheta domesticus” Journal of Herpetological Medicine and Surgery. https://meridian.allenpress.com/jhm.../Evaluation-of-Various-Calcium-fortified-High

6) Finke, et al, 2005, “Evaluation of Four Dry Commercial Gut Loading Products for Improving the Calcium Content of Crickets, Acheta domesticus” Journal of Herpetological Medicine and Surgery (2005) 15 (1) https://meridian.allenpress.com/jhm...Evaluation-of-Four-Dry-Commercial-Gut-Loading

7) Frye, F. 2007 “The importance of calcium in relation to phosphorus, especially in folivorous reptiles” The importance of calcium in relation to phosphorus, especially in folivorous reptiles | Proceedings of the Nutrition Society | Cambridge Core

8) Green, A. 2016. Meeting the Vitamin A Requirement: The Efficacy and Importance of β-Carotene in Animal Species. Meeting the Vitamin A Requirement: The Efficacy and Importance of β-Carotene in Animal Species - PubMed

9) McWilliams, 2008. "Nutrition Recommendations for some Captive Amphibian Species (Anura and Caudata) “ https://www.caza-narg.ca/ref/amphibian nutrition report CAZA 2008.pdf


10) Michaels, et al, 2014. "Manipulation of the calcium content of insectivore diets through supplementary dusting" , Journal of Zoo and Aquarium Research, 2 (3) usir.salford.ac.uk/id/eprint/36715/1/Manipulation%20of%20calcium%20content%20of%20feeder%20insects.pdf

11) Dugas, et al, 2013. "Carotenoid Supplementation Enhances Reproductive Success in Captive
Strawberry Poison Frogs (Oophaga Pumilio)" (PDF) Carotenoid Supplementation Enhances Reproductive Success in Captive Strawberry Poison Frogs (Oophaga Pumilio)

12) 10 year old frogs legs collapsing











 

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Discussion Starter · #5 ·
It may also be useful to talk about additional supplementation of Vitamin A.
Thanks for the suggestion. I had a disclaimer in an earlier draft that I wasn't going to go into breeding -- my intent here was for this to instruct newer keepers who needed a science-based antidote to misinformation and common-sense assumptions --- that seems to have fallen away at some point. I've added it back in.

Vitamin A and breeding needs to be another article. It takes too many hours to do something like this, and I need a little rest. :)
 

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Discussion Starter · #7 ·
This is wonderful, thank you for this. Would it be possible for you to do an analysis of the ranarium brand of supplements and include in the treatise post above? :)

Cal-Bee + D3 | Ranarium

Rana-Vit | Ranarium
please review
BIRKHAHN A-Vital 75 Gram (supplement for amphibians & reptiles)
Putting this here for now, and I'll integrate it into the first post shortly.

****

Birkhahn A-Vital

I could find no direct manufacturer information on Birkhahn A-Vital. The first five ingredients (translated from German by Google) according to a retailer’s listings/product label are:

Stärke = starch (a filler)
Tricalciumphosphat = Calcium phosphate
Gelatine = gelatine
Mannit = mannitol (a sugar substitute with poor intestinal absorption; probably used here as a filler or flavor enhancer) https://en.wikipedia.org/wiki/Mannitol
Tricalciumcitrat = calcium citrate

Though Birkhahn A-Vital contains all the major and minor vitamins of importance (though with a very elevated Vitamin A level, it is worth noting), it uses only unsuitable calcium sources (a common feature of many “legacy” supplements; Birkhahn A-Vital was formulated in the early 1990s) . Calcium phosphate cannot correct Ca/P ratios of insects because of its phosphate level, nor can calcium citrate as it contains insufficient amounts of Ca (3). For this reason, Birkhahn A-Vital is is not suitable for use with dart frogs.



Ranarium Cal Bee + D3
Cal-Bee + D3 | Ranarium

Though Cal Bee + D3 does contain a useful form of Ca (calcium carbonate) and Vitamin D3 neceesary for uptake of that Ca, it contains no further vitamins such as Vitamin A or E. It does contain a large amount (20%) of bee pollen. Bee pollen is a source of B-complex vitamins (though a highly variable source Dried bee pollen: B complex vitamins, physicochemical and botanical composition) (Chemical composition and botanical evaluation of dried bee pollen pellets)

I could find no studies whatsoever on the effects or value of bee pollen in amphibian diets.

Cal Bee + D3 is not a complete supplement for dart frogs, and contains an ingredient of questionable utility.

Ranarium Rana-Vit

Rana-Vit contains a useful form of Ca, as well as Vitamin D3 and retinol. The inclusion of bee pollen is likely intended as a source of B Vitamins; as mentioned, this is a highly variable source. Rana Vit includes a small amount (0.6%) of Maca root, a human food source that is sometimes used as a libido and sexual performance stimulant. I could find no studies whatsoever on the effects or value of Maca root in amphibian diets.

Aside from the mentioned ingredients of questionable value, Rana Vit is is suitable for use with dart frogs.
 

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Discussion Starter · #8 ·
OK, added to the main post, and I improved the formatting there.

As a kind of aside, in researching this I bumped into older threads with discussions of supplement R&D from @Allen Repashy . I suspect that some of the "me too" supplements (all the 1990's era CaPO4 based ones, for example) were formulated without any formula improvements, lab testing of ingredients, or vetting of manufacturing processes like Repashy did.

Since my recommendations above were intentionally pretty strictly science-based, these sorts of considerations aren't going to be part of that post -- but personally I think they're very relevant.
 

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Discussion Starter · #11 ·
I still throw Miner-All into my rotation for trace minerals here and there.
Yes, I agree that there's certainly room for educated, goal-driven rotation protocols by keepers who've thought through the possible benefits and possible risks and who have a solid baseline understanding of their frogs' health status and know how to recognize if that status changes.

I'd warn other readers of this against the "rotate supplements to make sure your frogs aren't missing anything" recommendations by people who are in the business of selling you supplements, or people who just crawled out of a time machine from 1985 and haven't caught up with the current state of product quality and formulations.
 

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With regard to the benefits of carotenoids, I can provide more references and more evidence for their health benefits (and vit A activity across different types of carotenoids). I'm in the process of moving house so don't have much time at the moment. But when I have a bit of spare time I'll post them here to be included.
 

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Discussion Starter · #13 ·
I'd love any info you have, but that would be included in some other write up. This one is intended for basic supplementation information and is directed toward novice keepers who may have absorbed misinformation.

Another writeup concerning supplementation for breeding, and for other needs that are over and above basic frog preventative health (e.g. carotenoids, UVB, avoidance of SLS, treatments for STS, MBD, seizures, etc) would certainly be valuable, and I'd be happy to collect information on it. :)
 

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Info on UVB and frogs would be much appreciated. Very confusing that stuff UVB is...
I also have some good references about this topic. I'll make sure to provide those as well.

@socratic: would you prefer that I post them here or send them in a message to you?
 

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Discussion Starter · #17 ·
Info on UVB and frogs would be much appreciated. Very confusing that stuff UVB is...
For now I think it is safest to say that there are no known captive species of frogs for which UVB is established by either research or common anecdotal cases to be necessary for a healthy captive life, and no known captive species of frog that cannot use dietary D3 supplementation exclusively for a healthy captive life.
 
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Socratic,

Is it still ok to gut load my crickets (sorry no dart frogs, but I keep mossy frogs, turtles, crested gecko, flying gecko, and a Cuban False Chameleon in separate enclosures) with a hearty mix of different kinds of fish flakes, oatmeal, and orange slices for hydration before dusting them with Repashy Calcium Plus ?
 

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Discussion Starter · #19 ·
What you describe there isn't gutloading -- it is feeding. It is fine to feed crickets; in fact, they'll die without eating. ;)

I hold my crickets exactly the same way, actually. I use organic oat bran instead of oatmeal (same thing, basically), but they seem to do well with that and some fish flakes. I think orange slices the very best hydration method for crickets and roaches, judged in terms of cricket lifespan and reproductive rate of roaches.

To repeat, though, none of this is gutloading.
 

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What you describe there isn't gutloading -- it is feeding. It is fine to feed crickets; in fact, they'll die without eating. ;)

I hold my crickets exactly the same way, actually. I use organic oat bran instead of oatmeal (same thing, basically), but they seem to do well with that and some fish flakes. I think orange slices the very best hydration method for crickets and roaches, judged in terms of cricket lifespan and reproductive rate of roaches.

To repeat, though, none of this is gutloading.

Agreed, feeding not gut loading. I'll make the switch to organic oat bran. I've seen Repashy Bug Burger but I've never tried it. I wonder if anyone on here has used it ? Once again I would dust my crickets every feeding time as I do now.
 
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