Poison Dart Frog Nutrition Guide
by Ed Kowalski
When keeping amphibians in captivity having a correct diet is one of the keys for long-term husbandry success. However as the understanding of the needs of the animals’ increases becomes apparent that a correct diet involves more than the items fed to the animals. There are other factors that should be taken into consideration such as vitamins and mineral supplementation and in fact even the light that the animal is exposed to could have an effect on the nutritional requirements of the animals.
The dietary needs of amphibians have been little studied but are similar to domestic animals. The reason that the information is lacking is due to the fact that the nutritional needs would need to be tested by withholding the tested nutrient and then analyzing the effects on the animal. While there is an increase in the interest in specific dietary supplements for amphibians there is still a little guesswork involved in the nutritional needs of the animals. However even with this drawback, the majority of amphibian nutritional needs appear to be within the ranges determined for other animals.
One of the first issues that should be addressed with the keeping of amphibians is the dietary requirement of the animals. All of the commonly available commercially raised invertebrates are not nutritionally balanced as a complete diet for amphibians. All purchased feeder invertebrates should be offered food for at least 48 hours before being offered as a food item to insure that the feeders have had a chance to replenish any lost proteins, fats and minerals. Many different diets can be used to accomplish this task although cruciferous vegetables and spinach should not be major components of the diet. Cruciferous vegetables in excess can cause problems such as goiter while spinach contains oxalates that may interfere with calcium. Many people use chicken mashes to feed crickets and other invertebrates. In general the better the diet fed the invertebrates used to feed your animals, the better the feeders are for the amphibians.
There are two possible ways to supplement the vitamin and minerals to the amphibians; these are as follows, dusting and gut loading. While some people use one to the exclusion of the other there is a significant benefit to overlapping the two methods. Originally gut loading referred solely to the attempt to adjust the calcium-phosphorus ratio of the feeder insects, however this phrase has come to mean any diet fed to the feeders. All of the other commercially used invertebrates (except for earthworms maintained in a calcium rich soil) have a negative calcium to phosphorus ratio. (The calcium to phosphorus ratio should be at least 1 to 1 and ideally closer to 2:1.) An improper calcium to phosphorus ratio is one of the most common sources of dietary calcium issues. The problem with trying to adjust the calcium-phosphorus ratio of the feeder via diet is that it often doesn’t succeed. (For example; with respect to crickets, only pinhead crickets achieve a positive calcium to phosphorus ratio). High calcium feeder diets need to be the sole diet offered for at least 48 hours prior to being offered as a food item. If there are any other food items available, the insects will avoid the high calcium diet negating any value of the diet. This should not be taken to mean that the feeder insects should not be fed prior to offering them as food to your animals. On the contrary, feeders like crickets, cockroaches and mealworms should be offered fresh food and a source of water for at least 24 and preferably 48 hours before feeding them out. This allows the feeders to replenish any lost vitamins or minerals during shipping or storage at the local pet store. Feeders that are stored in a decent food source like fruit flies do not need to be offered additional food before feeding them out.
A simpler method for adjusting the
vitamin-mineral content is by dusting the feeders with a balanced
vitamin-mineral mixture. A balanced
vitamin/mineral supplement will have a ratio of vitamin A to D3 to E as close to
10 to 1 to 0.1 as possible. The reason for this is that those vitamins compete
for absorption in the digestive tract and an imbalanced ratio will result in
deficiencies of one or two of these vitamins. When choosing a vitamin mineral
supplement, choose one that contains a preformed of vitamin A (typically
retinyl palmitate, retinyl acetate, or retinol, do not use one that contains
beta carotene as the sole source of vitamin A. The feeders can simply be treated with the
shake and bake method resulting in a light covering of the powder. 
There is a risk of over supplementation as well as under supplementation of many of the important vitamins and minerals. Vitamin A, D3, and E are all fat-soluble vitamins and may be over supplemented. Hypervitaminosis of A can result in secondary hyperparathyroidism (which is one of a couple of diseases that are often called metabolic bone disease). MBD may show up as deformation of the bones including those that are required for feeding. Without proper treatment the death of the animal is assured and even if treated the deformities will be permanent. Hypovitaminosis of vitamin A has been implicated in short tongue syndrome (STS), poor disease resistance, infertility, poor hatching rates, tadpole deformation and spindly leg syndrome (SLS). Severe cases of STS can result in a slow death by starvation as the frog becomes unable to capture prey as the tongue loses its stickiness. At this time, all of the data is pointing away from post-metamorphic frogs from being able to efficiently use beta carotene as a source of vitamin A. This is the primary cause of vitamin A deficiency in anurans as most of the dusting supplements on the market use beta carotene as the source of vitamin A. I have to note that this does not mean that the frogs do not require beta carotene for optimal health, it is of importance as an antioxidant as well as for color. The issues with beta carotene lead directly to one of the areas where we have seen the greatest amount of change in amphibian nutrition. One of the issues that has plagued captive bred and raised frogs are changes in coloration not only over time but over generations which has caused many people in the hobby to consider frogs that have been captive bred for multiple generations as being of poorer quality than wild caught frogs or those that have been captive bred for only a couple of generations. This is directly due to being fed a diet that is poor in both diversity and amount of carotenoids. There have been attempts (such as paprika) in the past to address but often the carotenoid sources were not selected with an eye towards those that were identified as being used by the frogs. It is only relatively recently has the hobby been able to access a premixed supplement that contains all of the vital carotenoids*. The best recommendation is to use a supplement that contains a diversity of carotenoid and should have the following at a minimum, astaxanthin, lutein, beta-cryptoxanthin, canthaxanthin, and beta carotene. There have been strong indications that not only do the carotenoids play important roles as sources of pro-vitamin A, anti-oxidants and pigments but are important as a probiotic as a carotenoid deficient diet results in a decreased beneficial microbe population on the frogs.
Hypervitaminosis of D3 can result in calcification of some
soft tissues as well as liver and kidney damage. Insufficient D3 can result in
another form of “MBD” as there isn’t enough calcium to support proper bone
formation and maintenance. The symptoms in this case are hard to distinguish
from excess vitamin A in the diet so the husbandry of the amphibian needs to be
carefully evaluated.
Narrow-striped dwarf siren with severe case of “MBD” from
feeding a diet consisting only of white worms which do not
contain vitamin D3.
One of the areas where there is a lot of confusion in the hobby revolves around the use of UVB lighting in addition to supplementing vitamin D3 via the diet to the animals. In a number of species including some that were previously thought to not require additional vitamin D3 (such as snakes), the animals often behaviorally seek to maintain levels of D3 and its metabolites (example, pre-vitamin D3) in the blood. The reason for this is that vitamin D3 probably should be considered more of a hormone than a vitamin. As noted above, feeding too much D3 to the animals is a problem as it can make an animal sick or even kill it, but if one uses a UVB source that the animal can access as it chooses along with a source of D3 in the diet, the animal will generally use behavior to optimize it’s D3 needs. In other words, it will not convert more D3 than it needs through exposure to UVB so adding a source of UVB can be very important provided the animals have some way to avoid exposure if the animal so chooses. This last point is critical as exposure to UVB lighting that the animal cannot avoid can also harm the animal through exposure burns or even eye damage.
To get the maximal benefit of the vitamin/mineral supplements for the amphibian, the following steps should be taken. The first is that the supplement should not be stored in a warm/moist environment. This causes a more rapid breakdown of the vitamins in the supplement. The second is that the supplements should be stored in the refrigerator to extend the shelf life. It is fine to remove what you would use in a 7-14 days at a time but the rest should be stored in the refrigerator. The third is to discard and replace the supplements every 6 months. Do not mix the supplements into feeder animal foods as this can cause significant imbalances in the nutritional value of the feeders. For example, fruit flies search out and store tocopherols (vitamin E), potentially resulting in levels hundreds of times higher than those found in the feed. These levels can in theory, get high enough to disrupt vitamin A and/or D3 function in the consuming animal.
*At the time of the writing of this article, I am only aware
of the Repashy brand products as containing the best carotenoid diversity for
reptiles and amphibians.