#gutload

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. 

I’d say the first step is to make sure you’re not over feeding your gecko.  This can be very relative, since what’s ‘enough’ for a gecko can vary drastically per individual.  But lizardbeans has a wonderful caresheet that also has a section that deals with ways to find out if your gecko might be overweight.  You can read that here. 

Usually, you see these pockets in female geckos who are overweight, and if your gecks are a bit overweight, you can lessen how much you feed them.  Just make sure to take it slow and only reduce food by a bit so you can monitor closely.  Cutting a gecko’s food, especially an overweight one, drastically and suddenly can damage their health, so go slow.  

Hi! Potato is an okay food for crickets – that is, they will survive on it – it’s just not a good gut load. 

Gut load can mean two things. One, exactly what it sounds like; feeding the insect right before giving it to your pet, so its digestive tract is stuffed with good stuff so that the insect is extra nutritious. This is the more technical use of the term. Two, people sometimes just use it to mean “feeding insects good food”. 

I’m first going to speak to the technical meaning of the term; gut load as a term specifically meant to mean filling the feeder insect’s digestive tract with higher nutrition material which will then be passed on to the reptile when the reptile eats the bugs. 

Insects will have nutritional content whether you gut load immediately before feeding or not. I’ve sometimes heard people say insects are nutritionally worthless without gut loading, but this isn’t true. (A dehydrated, starved insect will obviously be nutritionally deficient and that is not what I’m talking about.)   Certain insects contain better nutrition than others. For example, crickets and mealworms are not as nutritious as roaches, silkworms, or black soldier fly larva.  This has to do with their protein, fat, and moisture content, relative to chitin (exoskeleton), and also, very importantly, their calcium to phosphorus ratios.  

There are countless charts online regarding the nutritional content of various insects, and my advice is to compare several. Some may have errors; for example butterworms do not have high calcium but ridiculously high calcium is repeated in several charts that have simply taken their information from one inaccurate source (a seller).

This chart is taken from peer-reviewed journals and is accurate, though shorter than many other charts. 

Gut loading only happens 24-48 hours before feeding the insect to the pet. 

The main purpose of gut loading is to increase the calcium level of an insect, the same reason we dust our insects. Therefore, the foods one uses to gut load should be foods with a high calcium:phosphorus ratio. Phosphorus interferes with calcium absorption, so ideally, foods fed to our pet reptiles should have a 2:1 or better calcium:phosphorus ratio.

In addition, some gut loads increase protein. This is not as significant an impact as the calcium gut load can have. However, too much protein in many insect’s diets causes die off (in crickets) or worse (in roaches they will sequester it as uric acid in an organ called their fat body, which may then run the risk of causing hyperuricemia or gout in your pet reptile). Therefore high protein gut loads should definitely only be fed the day before being fed to the reptile.

There are commercial gut loads and they are the only ones that have actually been studied and shown to have an effect on the nutritional content of insects. Two gut loads we have data on are T-Rex Calcium Plus Food for Crickets and Mazuri Hi Calcium Gut Load. These actually do raise the calcium level of feeder insects and balance out the phosphorus levels. Remember, do not feed these except 24-48 hours before feeding off the insects. They should not be used as a regular diet.

Do not mix a commercial gut load with dusting your insects; do one or the other. These gut loads do significantly raise the calcium level of your feeder insects and you can give your pet too much calcium when doubling up.

Note: I’m editing this because pastrygeckos pointed out quite correctly that many times a gut load on its own isn’t enough -- it definitely depends on the gut load. To specify I mean do not double up dusting and commercial gut loads that have been verified through analysis to significantly raise insect calcium levels. There are many poor-quality commercial gut loads out there that may or may not do anything for the feeder insect’s nutritional content, and I do not recommend using them at all. If you choose to use a commercial gut load, go with a high quality, well studied brand so you know exactly what is happening with your feeders. In addition, if you “gut load” with vegetables and fruits, you must still dust your insects.

The other use of the term gut loading is simply what people mean by feeding their insects in general. They refer to feeding the whole colony, not the feeder insects they’ve removed to feed the next day and are feeding a special diet to. This means feeding a nutritious maintenance diet.

When we talk about gut loading with fruits and vegetables we do not actually know of the nutritional impact we are having on our insects, we are just guessing.* In my opinion, therefore, we should consider fruit and vegetable as a maintenance diet for our insects, along with a very high quality feed (not oats and wheat bran), rather than using it as a gut load (to the exclusion of dusting). The phosphorus levels in many insects will not be balanced out by the calcium levels in the vegetables and fruits people use for “gut loading”. They will also not change the macro-nutrients of our feeder insects. 

However, a feeder insect raised on a healthier diet will be a healthier meal for your pet! The better foods you feed your insects long term and right before you feed them to your reptile, the better. I personally feed vegetables with a high calcium:phosphorus ratio all the time, along with a nutritious dry diet.

My advice is to look at a chart of vegetables and foods for feeding reptiles, like a bearded dragon. They will have a list of great veggies suggested for feeding to your reptile as staples because they have high vitamins, and excellent calcium:phosphorus. The same vegetables that are ideal staples for a reptile (marked in green)are the vegetables that I feed to my feeder insects, such as collard greens, butternut squash, dandelion greens, alfalfa plant (not sprouts), and so on. (Note that potato is “feed rarely” because of its high phosphorus and oxalates. I do not give it to my feeder insects.)

For a dry diet, you want something with no more than 20% protein, and no more than 5% fat. As I mentioned before, too much protein can cause major problems, either in die-offs in your colony or causing health problems for your pet. For this reason avoid fish food, dog food, and cat food. You also want it to be high in vitamins and minerals, which is one reason why plain whole grains, like oats are less desirable. Wheat bran and oats are also both high in phosphorus. 

Many places sell “roach diet” which is also suitable as a cricket, superworm, and mealworm diet. Most of these, however, are actually poultry feed (specifically layer’s diet), and it’s much cheaper to buy poultry feed yourself. There’s often a markup when places repackage it for bugs. You just have to be careful the poultry feed does not have diatomaceous earth added, as this kills bugs in dry form. Two that are popular are Purina Layena Sunfresh Crumbles, and Albers All Purpose Poultry Feed. 

There are other options as well, especially if you are just keeping a few insects and not raising them. Total Whole Grain Cereal is an easy option you can buy at the grocery store! ZooMed Natural Bearded Dragon Food Adult Formula is another option. Both of these would be rather expensive to feed a breeding colony of insects long term, but work well when you are only feeding one or two reptiles.

I personally feed a variety of feeder insects (dubia roaches make up the staple); I feed my feeders a very nutritious maintenance diet as described here, dust my feeder insects appropriately with calcium, calcium with D3, and a vitamin mix on a regular schedule, and do not use a commercial gut load. Different keepers have different styles and techniques that work for them!

* I haven’t been able to find any information on this, at least, and that may have changed and such information may be available now. If anyone has found a scientific study that compares the nutritional content of insects before and after being fed an exclusive diet of certain fruits and vegetables, I would love to see it.