Reptile & Amphibian Forums

This is a topic that comes up from time to time as a practice that is bad for the frogs, typically with the comment that rodents are too high in fat and lipids for the frogs..

This is not true. When you compare commercially available feeder insects with rodents on a kcal basis, the fat and lipid content of rodents and the insects are very close. This is why corneal lipidosis is commonly seen in frogs that are only fed commecially reared insects.

The problem comes around because people feed the frogs on a volume basis as opposed to understanding the caloric needs of the frog. Rodents are more nutritionally dense (which can be seen by simply weighing the rodent and the insects). For example, a pinkie the size of an adult cricket actually weighs as much as 4 large crickets. If the frog is then fed the pinks with anything close to the frequency of offering crickets, severe overfeeding then results with the issues that come from obesity.

For those that are interested in reading up on this, I suggest the Nutrition chapter in Amphibian Medicine and Captive Husbandry as a good starter point.

Ed

I have to agree with you. Since my toad has not been eating I have been doing a lot of research. Both on pet owner web sites and academic articles. Only in the pet owner web sites do I ever see that an all rodent diet is all out bad for the toad.
One study I read compared the specific dynamic effect which is the tendency of the resting metabolic rate to increase after feeding. The study compared the rates of toads fed the same weight in crickets compared to mice. They predicted the all mice diet would cause the metabolic rate to be higher because of the higher protein content, but they found no difference in rates. Now this has nothing to do with obesity or lipidosis, but! if you know anything about cellular respiration you know that metabolism poses dangers to the organism because of producing free radicals... but the researchers found no difference in metabolic rates. They concluded that these toads evolved that trait so that they could grow really fast. After all, what matters in nature is reproducing and toads that eat a high rodent diet - grow faster - and reproduce more quickly.
Thus it makes sense that these toads would have a natural diet high in rodents. Contrary to what has been said though, no study has really been conducted which has specifically looked at their natural diets... also, someone mentioned these toads being nocturnal, but they are in fact diurnal.
Also, today I force fed my toad a small pinkie (put the head in his mouth and let the toad to the rest of the work). After he ate it the toad seemed more active - that is he actually moved today compared to his tendency to just sit all day and night. Pinkies have a much higher vitamin content, as well as other nutrients, so I figure a toad that isn’t eating would do better to have a fore fed pinkie than a single force fed cricket.

Actually there are a lot different studies that cover diets in anurans in the wild (I know I cited the horned frog one on this forum several years ago).

I'm not sure I would agree with you on the more vitamin part with the pinks and force feeding anorectic amphibians dense meals can cause problems with refeeding syndrome if you are not careful.

Ed

Well I have only force-fed one pinkie and I am going to wait 2 weeks to offer him another. I am hoping that the first one will get him to eat a second one after a couple weeks. Why wouldn't you agree that there is more vitamin content in a baby mouse than in a cricket? Everything I have come accross says that pinkies have a lot of vitamins that insects lack.

Also, could you send the citation of the article on horned toad diet?

Basso, N. G. and J. D. Williams. 1989. The diet of Ceratophrys ornata (Anura: Ceratophryidae) in Argentina. 1st World Congr. Herpetol. Canterbury.

and

Duellman, William E. and Miguel Lizana. 1994. Biology of a sit-and-wait predator, the leptodactylid frog Ceratophrys cornuta. Herpetologica. 50 (1):51-64.

With respect to the vitamin content, it depends on the food fed to the rodents when referring to the vitamins. While insects are low in vitamin D3, there isn't any guarantee that the pink will also contain vitamin D3 as they can also use D2 which cannot be used by the frog. As D2 is cheaper than D3, D2 is often substituted into the diet of animals (and people) that can readily use either one.... this is one of the reasons why the pink should be dusted with D3. In addition, pinks also tend to have a higher vitamin A as retinol level than insects which can throw off the absorbtion of D3 (as vitamin A, D3 and E all compete for uptake) and cause a form of MBD.

Ed

Ed

How necessary is vit D3 when using UVB light?

How necessary is vit D3 when using UVB light?

That depends on how long you have the lights on every day. What the distance between the light and your frog is, and what materials the light has to "shine through" to reach your frog. I still dust with vitamin D3 even though some of my lights are ultraviolet.

Well given that you are using the fluoro tube appropriately. i.e., max of 12 inches shining only through large mesh and on a 10-12 hour light period - I agree it is still probably a good idea to dust with D3 though. Compared to the UV/heat bulb I use on my turtle and used on my iguana the fluoro tubes have very little UVB rays.

the problem is that most bulbs that are reported to produce UVB may not actually produce UV in the correct wavelengths (280-315 nm). These results may be due to utilizing the incorrect photometer when measuring the wavelength (some recent data shows that using a broad range photometer can result in inconsistant results) and even narrow bands can provide the wrong data unless they are calibrated against a known standard.

In general, UVB supplementation should be utilized as a backup method for D3 supplementation (this is because photoconversion will only occur if there is insufficient D3 in the body).

Ed

Nice thread Edk, thanks for the post. There seems to be a lot of people on here that think feeding mice to Horned frogs is a sin =P. I've been feeding my frog a large mouse every 3 weeks or so, and he is perfectly healthy and 3 years old now. He has not gotten obese, he looks rather plump after eating a mouse as you can see in the pic below (that was a big mouse), but after he digests it he's actually pretty slim for a pacman.

To continue this a little more..
A large mouse typically weighs close to 29 grams which would be the equivalent to more than 100 large crickets.

Here is a picture I have of corneal lipidosis in a grey tree frog that has only ever been fed crickets.

Ed

I have seen that before in a horned frog who was fed pretty much nothing but mice for 6 years.

It can and does occur in rodent fed frogs (just like it does in frogs fed nothing but insects but it has just as much to do with the frequency of feeding as it does with what is fed. If you keep feeding the frog far above its metabolic needs then the excess nutrients will be converted to fats and stored in the body. The lipid content builds up until you get the problem with corneal lipidosis.
Also female frogs seem to be more prone to it than males due to the storage and metabolism of fats for egg formation.

Ed

Hi Ed,
Just curious why D3 is missing from a captive diet in the first place. What do they eat in the wild that is so different from what we feed them that they need to be supplemented with D3 in order to prevent MBD? Is it just lack of UVB light? Or mass produced insects that don't have the same nutrition value as wild insects? Combination of the two?
I knew of someone that fed his horned frog nothing but calcium dusted fish, and the frog lived for 15 years! Is this just an anomaly, or perhaps the frog was wild caught and spent its preformative years soaking up the sun and eating the native food?
Maybe the MBD problems are more a symptom of overbreeding rather than lack of dietary vitamins? Just a thought. Thanks for your response.

snip "Hi Ed,
Just curious why D3 is missing from a captive diet in the first place. What do they eat in the wild that is so different from what we feed them that they need to be supplemented with D3 in order to prevent MBD?"endsnip

In the wild they have access to unfiltered UVB which allows them to convert provitamin D to D3. This is not that easy to supply in sufficient quantities in captivity at this time and UVB should be considered a back-up method of vitamin D3 supplementation.

snip " Is it just lack of UVB light?"endsnip

Yes (see above)

snip "Or mass produced insects that don't have the same nutrition value as wild insects?"endsnip

They do not have the same nutritional value as wild insects. For example mass produced insects tend to have a higher saturated fat profile (for one difference).

snip "I knew of someone that fed his horned frog nothing but calcium dusted fish, and the frog lived for 15 years! Is this just an anomaly, or perhaps the frog was wild caught and spent its preformative years soaking up the sun and eating the native food?"endsnip

It depends on the fish. Many fish have adequate supplies of D3 which would have met the frog's nutritional requirements.

snip "Maybe the MBD problems are more a symptom of overbreeding rather than lack of dietary vitamins?"endsnip

I have seen this mentioned in a couple of places but this isn't supported by the literature or the data. (see http://www.tracyhicks.com/MBD.htm for an older review of MBD).

Ed