Avoiding Metabolic Bone Disease (MBD) in Tortoises Foods: Database of Plants
Considering feeding supermarket produce to your animals? Investigate first.
Further down the page, you will find a table with nutritional components of many items that have been fed to tortoises.
A grazing tortoise needs a high fiber, high calcium and low phosphorus diet. Some supermarket produce items may seem healthy at first glance, but when investigated more closely, many of these items are poor food choices, and can lead to serious health problems.
Some tropical species such as Redfoots, Hingebacks, and Box Turtles tolerate some animal protein in the diet, as well as a little more vegetable protein and sugar than their grassland grazing cousins. The balance of calcium to phosphorus remains critical for all species, as does water and oxalate content.
A calcium to phosphorus ratio of at least 2:1 must be maintained.
Example #1: You wish to offer your tortoise green peas. Green peas have a Ca to P ratio of 25:108. Doing some simple math, the Ca to P ratio is far too low, equaling 1 part calcium to more than 4 parts phosphorus. This excess phosphorus cancels out the calcium, leaving the tortoise from being able to properly metabolize (and use) the calcium in this food item. Excess phosphorus and not enough calcium leads to poor, uneven growth and weak, porous bone structure. This is known as “Metabolic Bone Disease” (MBD) or “Nutritional Secondary Hyperparathyroidism” (NSHP). Once MBD damage occurs, it cannot be reversed. Providing an optimal diet can, however, keep MBD from further progression. MBD is a very common problem in pet tortoises. Providing sufficient natural sunlight is also essential in making ultraviolet radiation A and B available, which is needed to properly synthesize and use calcium.
Example #2: You wish to offer your tortoise beet greens (tops). While the calcium to phosphorus ratio IS close to 2:1, the high oxalate content makes this a poor food choice. Oxalates are a calcium-inhibiting compound, (they have the potential to bind calcium and other trace minerals) making them unavailable for the tortoise to use. This starves the tortoise of essential calcium needed to remain healthy. Excessive oxalates in the diet contribute to significant renal and bone development problems.
If your tortoise is on an excellent, varied diet, offering a bit of one of these items probably won’t cause harm, but including them as a regular, or significant part of the diet can cause problems from mild illness to death.
Tortoises on poor diets, and not provided with excellent captive husbandry (such as full-spectrum sunlight, needed for vitamin D3) are also likely to develop bladder stones or renal problems. While small bladder stones don’t seem to cause any distress, they can grow, become quite large, and can eventually kill a tortoise. Symptoms of a bladder stone aren’t often noticed until illness is advanced.
Grazing tortoises do not have the type of digestive system necessary to break down excessive sugars. Excess water and sugar can create intestinal problems (diarrhea, digestive flora imbalance and parasite problems.)
One must weigh the good along with the bad when choosing any food item. Also keep in mind that many commercially available vegetable and fruit products may contain pesticide residue, and many commercially prepared diets contain items that tortoises were never intended to eat.
Tortoises have kept themselves healthy in the wild for millions of years. Making wise food choices is a great way to keep them happy and healthy!
Items in BOLD indicate why the specific food item is not healthy for a tortoise.
There is no table for commercially available fruit-for species like the desert tortoise, sulcata, Mediterranean species, fruits are not a recommended part of the diet. They are extremely high in sugars, which these types of tortoises do not find in the wild, and can cause a host of health problems. A few common fruits have been added, but the absence of fruit in these tables does not imply they should ever be fed.
|Item||Value||Ca/P Ratio||Oxalates (mg/100g)||Water (%)||Fiber (g)||Total Sugars (g)||Protein (%)|
|Apple||100 g||5:11||0.50 ± 0.10||85.56||2.4||10.39||0.26|
|Avocado MAY BE TOXIC TO REPTILES||100g||12:52||73.23||6.7||0.66||2.00|
|Beets||100g||16:40||81.10 ± 23.80||87.58||2.8||6.76||1.61|
|Bell Pepper, Green||100g||10:20||93.89||1.7||2.40||0.86|
|Bell Pepper, Red||100g||7:26||1.1||91.21||2.1||4.20||0.99|
|Bell Pepper, Yellow||100g||11:24||92.02||0.9||unk||1.00|
|Green Leaf Lettuce||100g||36:29||94.98||1.3||0.78||1.36|
|Kale||100g||150:92||1.9 ± 1.4||84.04||3.6||2.26||4.28|
|Lettuce, Red Leaf||100g||33:28||95.64||0.9||0.48||1.33|
|Okra||100g||82:61||61.5 ± 7.8||89.58||3.2||1.48||1.93|
|Olives, Black||100g||88:3||27.4 ± 19.2||79.99||3.2||0.00||0.84|
|Sweet Potato||100g||30:47||29.1 ± 39.4||77.28||3.0||4.18||1.57
|Tomato, Red||100g||10:24||6.50 ± 5.80||94.52||1.2||2.63||0.88|
Glossary of Terms
- PHYTIC ACID: Phosphorus as stored in plants. Phytic acid inhibits the uptake of calcium and can cause problems with Metabolic Bone Disease, renal failure, shell pyramiding and bladder stones.
- CYANOGENIC: Contains dietary cyanide.
- GOITROGENIC– A food item which contains “iodine binders.” When iodine absorption is blocked a goiter may form, impairing thyroid function and causing hypothyroidism.
- SAPONIN : Any of a class of glycosides, found widely in plants, that have detergent properties and form a lather when shaken with water..Most saponins can be toxic and speed up hemoglobin degradation.
- TANNIN: a glucoside.
- OXALIC ACID: Oxalic acid binds with important nutrients, making them inaccessible to the body, regular consumption of large amounts of foods high in oxalic acid over a period of weeks to months may result in nutrient deficiencies, most notably of calcium. Oxalic acid is a strong acid, and is irritating to living tissues all by itself. Extremely high doses are fatal. Oxalates, on the other hand, form tiny little insoluble crystals with sharp edges, which are also irritating to tissue. So, high levels of oxalic acid/oxalates in the diet lead to irritation of the digestive system, and particularly of the stomach and kidneys. They may also contribute to the formation of kidney stones (the most common form of kidney stone is composed of calcium oxalate). Also results in bladder stones in tortoises.
- GLYCOCIDES: Compounds formed from a simple sugar and another compound by replacement of a hydroxyl group in the sugar molecule. Many drugs and poisons derived from plants are glycosides. Digitalis is a good example.
First Published 3/11/2001 Last Update 4/17/2017
Special thanks to Linda King for her kind assistance regarding tortoise diets and potentially harmful plants.