Selecting Healthy Tortoise Foods-A Guide

Annie Lancaster

So you want to feed store bought produce to your animals?

 A grazing tortoise needs a high fiber, high calcium and low phosphorus diet.  A calcium to phosphorus ratio of at least 2:1 needs to be maintained.  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 irreversible health problems.

Some species such as Redfoots, Hingebacks, and Box Turtles tolerate some animal protein in the diet as well as a little more vegetable protein and sugars than their grassland grazing cousins, but the balance of calcium to phosphorus remains critical, as does water content , oxalate content.

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.)

Many of these items are also very high in oxalic acid. Oxalates can contribute to significant renal and bone development problems.  One must weigh the good along with the bad when choosing any food item.

Items marked with RED are of items to avoid.  BLUE indicates the component, contents, etc. that may be harmful.  Do your homework and if at all possible, offer natural items (rather than those in the supermarket.)   Natural foods after all, are what a tortoise would generally eat if not in captivity, and duplicating wild diets as closely as possible will help to maintain peak health. 

Tortoises have kept themselves healthy in the wild for millions of years.

** = data unavailable  DM = Dry Matter Basis

 

Item Serving Size Oxalic Acid g per 100g Ca/P  (in mg) Water Content (%) Fiber Content (g) Total Sugars (g) Protein Content (%)
Apple 100g ** 5/11 83.90 12.25

10.10

0.91
Broccoli 100g .19 47/66 90.69 13.59 1.70 13.49
Bok-Choy/Pac Choi 100g ** 105/37 95.32 1.00

1.18

1.50
Cabbage 100g .10 40/26 92.18

2.50

3.20 1.28
Chard (Swiss) 100g ** 51/46

92.66

1.60 1.10

1.80

Banana 100g ** 5/22 74.91 2.60 12.23 1.09
Watermelon 100g ** 7/11 91.45 0.40 6.20 0.61
Chives 100g 1.48 92/58 90.65 2.50 1.85 3.27
Iceberg Lettuce 100g .33 18/20 95.64 1.20 1.97 0.90
Romaine Lettuce 100g .33 33/30 94.61 2.10 1.19 1.23
Tomato (Red) note: leaves, stems are toxic 100g ** 10/24 94.50 1.20 2.63 0.88
Cauliflower 100g .15 22/44 91.91 2.50 2.40 1.98
Kiwi 100g ** 34/34 83.07 3.00 8.99 1.14
Red Leaf Lettuce 100g .33 33/28 95.64 0.90 0.48 1.33
Collard Greens 100g .45 145/10 90.55 3.60 0.46 2.45
Zucchini (Courgette) 100g .02 15/38 94.64 1.10 1.73 1.21
Red Cabbage 100g ** 45/30 90.39 2.10 3.83 1.43
Beet Greens 100g .61 117/41

91.02

3.70 0.50 2.20
Parsley 100g 1.70 138/58 87.71 3.30 0.85 2.97
Spinach 100g .97 99/49 91.40 2.86 0.42 2.86
Green Bean 100g .36 37/38 90.27 3.40 1.40 1.82
Purslane 100g 1.31 65/44 93.32 ** ** 1.30
Green Pea 100g .05 25/108 78.86 5.10 5.67 5.42
Brussels Sprout 100g .36 42/69 86.00 3.80 2.20 3.38
Cucumber 100g .02 16/24 95.23 0.50 1.67 0.65
White Clover (Dry-Hay) DM 92% HIGH ** ** 20.90 ** 21.40+
Alfalfa Hay DM 90% ** 12/51 ** 27.0 ** 15.3+
Mustard Greens
Chinese Cabbage (pe-tsai) 100g ** 77/29 94.39 1.20 1.41 1.20
Yellow Corn 100g .01 2/89 75.96 2.70 3.22 3.22

When compared to what we know about other food items, the differences become very clear.

Opuntia Cactus 100g ** 164/16 94.12 2.20 1.15 1.32
Bermuda Hay DM 92% ** ** ** 27.60 ** 5.50-8.00
Hibiscus Flower 100g ** 215/37 ** ** ** 0.96
Grape Leaf 100g ** 363/91 73.30 11.0 6.3 5.6
Shepherd's Purse 100g ** 208/86 ** ** ** 4.20
Ryegrass Hay DM 86% ** ** ** 26.00 ** 7.40
Dandelion 100g ** 140/42 ** 3.50 ** 2.70
Mallow-Common 100g ** 249/69 ** ** ** 4.40
Timothy Hay DM 89% ** ** ** 30.20 ** 6.30
Orchard Hay DM 89% ** ** ** 30.00 ** 8.00

 

The plants listed below can potentially cause problems with bladder stones, renal failure, and some are listed in databases as poisonous.

Please use the utmost care when deciding what plants you offer to your tortoises!  While a few of the plants listed are OK to use with cautious moderation, (clover, for example) overeating of any of these plants may cause serious illness

 

VETCH Vicia spp are OK but the Lotus spp can be toxic. Also very high in protein when plants are young...use in moderation, if at all.
RAPE Opinions vary as to toxicity and cultivars developed from the wild  http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Brassica+rapa+campestris Potentially toxic due to glucosinolates http://www.rvc.ac.uk/Estates/plants/brassnap.htm    Brassicas are generally high in goitrogens.
KELP Extremely high in sodium unless pharmaceutically refined, do NOT feed "dried" kelp to tortoises under any circumstances, unless sodium cntent can be verfied as absent. 
ALFALFA Far too high in vegetable protein.  Avoid entirely.
CEREAL BUCKWHEAT This is #2 on the list of Oxalic acid containing plants - go to the ARS High-Low chemical enquiry database and type in oxalic acid: http://www.ars-grin.gov/duke/highchem.html
DICHONDRA Legume, should be used in strict moderation in  broadleaf eatng species only.
WILD MUSTARD, MUSTARD GREENS High in oxalic acid and goitrogens,  Negative Ca:P ratio.
COLLARD GREENS (see table above) High in goitrogens and phytic acid.
IMPATIENS High in oxaclic acid/oxalates.
MILK THISTLE When grown on nitrogen rich soils, especially those that have been fed with chemical fertilizers, this plant can concentrate nitrates in the leaves. Nitrates are implicated in stomach cancers." Ref: PFAF http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Silybum+marianum

If used, grow in un-enriched soil ONLY.

STINGING NETTLE Appears on toxic lists, unsure of toxic properties, so the verdict is still out.   http://www.ansci.cornell.edu/plants/alphalist.html

When growing,  unpleasant to humans who touch it

BABY'S BREATH Could be any of the following: Euphorbia corollata (Wild spurge; Prairie Baby's Breath Euphorbiaceae) - toxic & carcinogenic http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Euphorbia+corollata Galium mollugo (Hedge bedstraw); False Baby's Breath; False Baby's-breath Rubiaceae G. elatum. G. erectum) - oxalic acid Gypsophila oldhamiana (Manchurian baby's breath; Manchurian Baby's Breath; Oldham's Baby's-breath Caryophyllaceae) - saponins http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Gypsophila+oldhamiana Gypsophila paniculata (Baby's breath; Tall Baby's-breath Caryophyllaceae - saponins) Ref: PFAF http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Gypsophila+paniculata  

When in doubt of true species name, play it safe. Common names can be dangerous.  

CLOVER (see table above) Clovers are often listed on toxic plant lists which can worry and confuse people. The reason is clover can, if damaged by frost or wind-scorch, develop cyanogenic compounds. Clovers also contain high levels of  protein. The proportions of the clovers and other leguminaceae needs to be kept as low as possible, particularly as they germinate more quickly than other seeds, and can suppress growth of other nutritionally important plants.  

Offer clovers only in strict quantities.

FLAX Cyanide producing compounds.  http://www.ansci.cornell.edu/plants/alphalist.html

Another plant with a common name that can be a harmful species if the wrong one is chosen..   

ITALIAN DANDELION (Chicorium intybus) This is a Chicory which is good food and much liked but safe only when grown on unenriched soil, as it is one of the plants that is a 'nitrogen sponge', indeed is actually used to 'clean up' the soil of nitrates. Feed sparingly if growing in desert soils...

DO NOT GROW IN ENRICHED SOILS!

ENDIVE Cultivar of chicory, OK to feed,  but see information regarding chicory.
LETTUCES: Iceberg, and similar (see table above) Very low nutrition and Ca:P negative. Can cause loose stools, digestive upset and vitamin deficiencies.
CHINESE LANTERN, Physalis spp Poisonous leaves and stems.
BEGONIA - semperflorens  Flowers; leaves -calcium oxalate crystals
PRIMROSE

Only wild desert primroses are considered safe, wild Gopherus are observed eating them, OTHERS (cultivars) are considered to be potentially toxic.

PORTULACA (moss rose)

Leaves; Flowers- Grandiflora - Plants may contain up to 9.3% oxalates and are known to cause acute oxalate poisoning, this one is dangerous.

LAVENDER-Lavandula angustifolia Found on various toxic lists-unsure of safety for reptiles.
RUSSIAN VINES Extremely  high in oxalic acid
Wild Carrot-Daucus carota High oxalic acid, goitrogens, tannins, negative Ca:P ratio. 

Roots not naturally consumed by wild tortoises anyway.

Common Sorrel- Rumex & Oxalis ssp Very high in oxalic acid. http://www.ars-grin.gov/duke/../cgi-bin/duke/highchem.pl
'Pink Purslane'-Leaves; Flowers- Montia sibirica - Portulacaceae 5th highest oxalic acid containing genus
Parsley Extremely high Oxal:Ca ratio = 14:1 (also causes diarrhea) 
Curled dock- Flowers; Leaves; Root - Rumex Dangerously high in oxalic acid
Black mustard- entire plant- Brassica Nigra Seeds and pods toxic.
Buckwheat, Polygonaceae Very high in oxalic acid
Wisteria spp. (wisteria) The seed of all members of this genus is poisonous.  http://website.lineone.net/%7edellantonio/engweb/page3.html http://www.ars-grin.gov/duke/highchem.html
Forsythia ssp Contains glycoside.
Chickweed Contains saponins.  Offer in strict moderation.
Saint Johns Wort - Hypericum Entire plant toxic  http://envhort.ucdavis.edu/ce/king/PoisPlant/Tox-SCI.htm
JOHNSONGRASS-Sorghum halepense  Leaves and stems, especially young plants. Contains cyanogenic glycoside.   http://vet.purdue.edu/depts/addl/toxic/plant43.htm
Croton, Codiaeum spp All parts toxic, alkaloids, irritant sap. http://www.ces.ncsu.edu/depts/hort/consumer/poison/Codiava.htm http://website.lineone.net/%7edellantonio/engweb/page3.html
BROAD LEAFED TREFOIL Lotus corniculatus is toxic: "All parts of the plant are poisonous, containing cyanogenic glycoside (hydrogen cyanide)http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Lotus+corniculatus http://www.ansci.cornell.edu/plants/alphalist.html http://herbwisdom.tripod.com/toxic.htm

GLOSSARY OF TERMS USED

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 forms,  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.
GLUCOSIDE: See glycoside. A glycoside in which the sugar constituent is glucose.
OXALIC ACIDOxalic 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.
GLYCOSIDE:  Glycosides are drugs used for treating heart disease in humans and animals. (Digitalis is derived from the foxglove plant for example) and ingesting these plants can cause serious illness.  Symptoms include diarrhea, vomiting, dizziness, loss of consciousness and heart failure.

 

Special thanks to Linda King for her assistance regarding tortoise diets and potentially harmful plants.

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References: United States-Canadian Tables of Feed Composition, National Academy of Sciences

USDA Nutrient Database

Wild Edible Plants

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