do you happen to have that gutloading info/illustration, with the empty taco shell analogy? I cant for the life of me find it or remember who i saw it from...
It’s wasn’t me! I don’t find that graphic to be particularly accurate, though doing a search I couldn’t find it again.
Feeder insects are indeed deficient in some nutrients. However, they are more like full tacos missing only one or two ingredients, and just feeding healthy fruits and veggies to them will not help with those deficiencies.
Insects have nutritional content without being gutloaded. They are adequate for most minerals other than calcium, and they contain fat and protein.
Here is some nutritional content of common feeder insects, without gutloading.
Not all feeder insects are fed at all before feeding – for example, it’s best to keep BSFL cool and unfed before feeding them to your pet. They have a very good calcium:phosphorus ration and don’t even need to be dusted, though they are deficient in some vitamins. (As with most larva, smaller BSFL are lower in fat than larger ones, so the smallest that will be accepted by the reptile should be fed.)
The main issue is that most commonly fed insects have a poor calcium to phosphorus ratio, and lack vitamins. You typically want your pet’s food to have a 2:1 Ca:P ratio.
Here is information on various insects’ Ca:P ratios.
Now, this can be fixed in a variety of ways. One is to dust the insects with proper calcium and vitamin supplements.
The other is to use a gutload that actually works – and there aren’t many of these. The only one I can recommend is T-Rex Calcium Plus Food for Crickets. From that first link, “It should be noted however that many commercially available gut-loading diets failed to increase the calcium content of crickets presumably due to improper formulation.” Most tested gutloads simply didn’t correct the Ca:P ratio or help with the lack of vitamins. One thing that seems to be a problem is most gutloads use too large a calcium particle and the insects literally eat around it. (It is cheaper than using the extremely finely ground calcium. This is also why it’s hard to make your own gutload; it’s not easy to find calcium ground fine enough and readily ingested.)
Note that gutloading is very different from simply feeding your insects a nutritious diet. The term has been diluted to mean maintenance feeding, but this is inaccurate and not helpful in the discussion of feeder insect nutrition. Formal gutloading must be done within 24 - 48 hours of the insect being fed and no longer (and nutritional levels decline after 24 hours), and is a very specific high-calcium and vitamin diet. Simply feeding the insects nutritious food like veggies will not correct the Ca:P ratio! Feeding an insect colony gutload constantly will likely result in die-off so they can’t be fed indefinitely.
Maintenance diets are important to create a healthy, nutritious feeder overall – obviously a starved feeder will be less nutritious than a healthy one. Ideally they should eat a moisture-rich, vitamin-rich, varied diet for the feeder’s own health.
I recommend using this guide to choosing vegetables (focusing on the “green” rated veggies whenever possible) for your feeders’ maintenance diet, and feeding a nutritious grain-based staple with less than 20% protein as well, such as DE-free poultry mash (Purina Layena Sunfresh Crumbles or Albers’ All Purpose Poultry Feed are the two I know of), Total Cereal, or Natural Bearded Dragon Food Adult Formula. Just keep in mind, this diet is not a gutload.
Here is a really good study which covers why gutloading is difficult and sometimes unreliable (rates of ingestion at different instars [ages], optimal ways to offer the food, etc.).
I don’t believe these articles are available for free online (however, you can purchase and download them if not) but I highly recommend these studies evaluating different commercial gutloads available:
Finke MD. 2003. “Gut loading to enhance the nutrient content of insects as food for reptiles: A mathematical approach.” Zoo Biology 22: 147-162.
Finke, Mark D., S. Dunham, and Christabel A. Kwabi. 2005. "Evaluation of four dry commercial gut loading products for improving the calcium content of crickets, Acheta domesticus.“ J Herp Med Surg 15.1: 7-12.Finke, M. D., S. U. Dunham, and J. S. Cole. 2004. "Evaluation of various calcium-fortified high moisture commercial products for improving the calcium content of crickets, Acheta domesticus.” J Herp Med Surg 14.2: 17-20.
These studies are why I only recommend the T-Rex. Some commercial gutloads such as Mazuri Hi Calcium Gut Load rate higher than a maintenance diet, but I don’t know if they properly correct the Ca:P. Other gutloads have come out since the study was conducted, but because we don’t have any scientific analysis of them I can not recommend them.
In addition, feeding insects with plant-based vitamin A gutload may not translate to the reptile being able to use that vitamin A, particularly in strict insectivores. There have been many cases of reptiles like chameleons suffering from vitamin A deficiency despite eating gutloaded or dusted insects. Make sure that for strict insectivores/carnivores the vitamin A in the supplement is retinol (animal source), not carotenoids (plant source).
Alternatively, one can dust insects and feed a nutritious maintenance diet. My reptile vet is anti-dusting (he only recommends T-Rex gutload and no other options) but this is definitely not a universal view from reptile vets. Many will recommend dusting. My vet’s concern is hypercalcaemia from the fact that dusting supplements are not measured or exact, or vitamin D overdose (the latter is definitely a problem with certain dust brands; here is a clip from an article on vitamin D overdose from Douglas R. Mader, DVM).
The two dusting regimens I personally recommend are:
Dusting with Repashy Calcium Plus with every insect feeding.
or
A schedule of rotation for different feedings through the week, using a calcium with D3, a vitamin supplement, and possibly a plain calcium.
I waited until several breeders and other keepers had good success with the Repashy Calcium Plus before switching to it, since it seemed like an all-in-one wouldn’t be adequate or might result in excesses of some nutrients and lack of others. But it’s well accepted and seems to work! If anyone has encountered problems with this supplement I would like to hear it, though.
Not all dusts are created equal, just like gutloads. For plain calcium you have many options, such as human grade calcium powder. For calcium with D3, I have had good success with ZooMed Repti Calcium with D3. I also like ZooMed Reptivite for a vitamin supplement.
Avoid these supplements: Fluker’s Calcium with vitamin D3 (too much D3), Rep-Cal Calcium with vitamin D3 (too much D3), Exo Terra Multi Vitamin (beta carotene instead of pre-formed vitamin A, no B12).
Note that dusts must be used immediately before feeding the insects, as many insects will quickly groom them off.
The amount you use is far lower than you’d think! Read the instructions and be sure you’re *lightly* dusting with the vitamins and calcium with D3 on only the number of insects recommended for your pet’s weight.
I personally do not suggest using T-Rex (gutloading) and dusting, as the risk of hypercalcaemia and vitamin overdose increases. Both are adequate on their own for most animals, though laying females may benefit from additional plain calcium. It can also be dangerous to use both a supplement with D3 and UVB lighting, which is why there are different “indoor” and “outdoor” supplements available from many companies. Not all UVB lamps are created equal so this may depend on your setup. Always be sure your animal can choose between basking under the UVB and finding a shady place.
I know this isn’t the short and sweet infographic that you were looking for, but I find those graphics misleading and lacking very important information. Reptile nutrition, gutloading, and supplements is not a simple topic!
This is just my interpretation of the scientific data available; I hope the links and resources provided will help others come to their own conclusions.
That said, now I really want tacos.
