Conflicting advice on vitamin D and calcium supplementation

[The_Four_Toed_Edward]

I am worried whether my tortoise is going to get enough vitamin D here in Finland, so I did some research. Unfortunately the advice I found was conflicting, and as a new keeper I don’t know what advice is good and which sources to trust. So, I decided to turn to you with my questions and the answers I found. I will list under the question the answers I got with bullet points. The number in brackets coincides with the numbers listed down in my sources list.

So tell me, what answers would you give to my questions? Is the info I found correct? Are the sources I found good? I would love to hear your opinion and the arguments behind it.

What is the proper Ca: P? Why should I use calcium supplementation?

• It is usually advised that the Ca: P ratio of the total ration is between 1:1 and 2:1. (2)
• For tortoise diets, the traditional recommendation for calcium to phosphorus ratio (Ca: P) is 2:1 at the minimum. A ratio of 5:1, or higher, would be even better. (3)
• Based on newer studies, the need for calcium in tortoises may be even greater than previously thought. For example, a recent study done on plants eaten by Egyptian tortoises in the wild revealed that the mean Ca: P ratio was about 14:1. The Ca: P ratio ranged from 3.92 to 32.44 (The Batagur #2, TTPG, 2012).(3)
• The calcium-to-phosphorus ratio of captive diets is also typically far lower overall than is seen in the wild. Some typical examples include Plantago sp., with Ca: P ratios of above 20:1 and Opuntia sp., where Ca: P ratios can be as high as 78:1. (6)
• In order to make bones less brittle, we mix in some phosphorous for toughness, in a ratio of about three to four parts calcium to one part phosphorous. This is called the Calcium: Phosphorous Ratio, abbreviated Ca: P. A good Ca: P would be 2:1, a poor one would be 0.5:1. Too much phosphorus in relation to calcium and the bones get soft. (7)
• You can sprinkle some phosphorus free calcium carbonate powder on foods, especially if you use grocery store greens, to up the calcium content. (3)
• There is no reason to be afraid to offer supplemental calcium ato give our tortoises the best chances for success. (4)
• Calcium is essential for healthy blood and also helps to regulate heartbeat. (6)
• In addition, calcium assists in the process of blood clotting and prevent the accumulation of too much acid or too much alkali in the blood. It also plays a part in muscle growth, muscle contraction nerve transmission. (6)
• Calcium aids in the body’s utilization of iron helps activate several enzymes (catalysts important in metabolism) and helps regulate the passage of nutrients in and out of cell walls. (6)
• One problem in relying exclusively upon dietary selection is that many plants that on the surface appear to offer good, or positive calcium-to-phosphorus ratios, also contain chemicals that inhibit calcium take-up. (6)
• Vitamin and calcium supplements: Think of these as insurance- their purpose is to make sure the tortoises get everything they need even if the food we offer may be lacking in something. (7)

Why should I use reptical?

• Cuttlefish bone is a long-standing method of providing extra calcium to tortoises, and especially to turtles, as it floats readily in water. The main chemical constituents of cuttlebone are calcium carbonate, sodium chloride, calcium phosphate, magnesium salts and an abundance of micro-trace elements. Despite its high gross calcium content, cuttlefish bone is relatively poorly absorbed, and as such should not be relied upon as the sole source of calcium supplementation. It can, however, be employed as a secondary source. (1)
• On balance, the safest and most effective calcium supplements for routine use with captive tortoises would appear to be a calcium carbonate based, phosphorus-free ground calcium powder, preferably of commercial quality, either with or without added vitamin D3. (1)
• Reptical with D3- 13.7 IU per gram of powder (4)

What happens if my tortoise gets too much calcium? How high of a risk is there for that?

• In theory, excessively high intakes of calcium may interfere with the absorption of other nutrients such as iron and zinc, however, in chelonia we are not aware that such effects have been demonstrated. Other potential adverse effects of chronic intakes of high doses of calcium include Hypervitaminosis-D in the case of supplements containing both calcium and vitamin D. (1)
• Recent human studies indicate that increased intake of calcium does not increase risk of kidney stones. However, restricting dietary calcium may increase urinary excretion of oxalate which in turn increases risk of kidney stones in addition to causing bone developmental problems. (1)
• The indiscriminate use of mineral supplements is a highly dangerous practice for several reasons: If the base ration already contains sufficient mineral content excessive supplementation may result in toxic levels or mineral imbalances. Metabolic bone disease can result from excessive mineral intake as well as deficiency. (2)
• High amounts of calcium in the form of mineral supplements may not be digested and used by the animal, and this calcium can pass through the digestive tract and interfere with the availability of other minerals (eg copper, iron, zinc) in the ration by : Competing for receptor sites in the gastrointestinal tract and Binding with other minerals making them unavailable to the animal. (2)
• It is generally known that too much calcium results in secondary deficiencies of zinc, copper and iodine, mal-absorption of essential fatty acids, and formation of calcium-containing bladder stones. (5)
• In theory, excessively high intakes of calcium may interfere with the absorption of other nutrients such as iron and zinc, however, in we are not aware that such effects have been demonstrated. Other potential adverse effects of chronic intakes of high doses of calcium include Hypervitaminosis-D. (6)

How much calcium should I give my tortoise and how often?

• If mineral supplements have to be given to avoid deficiency disease because the base ration is inadequate, they should be used sparingly and with caution. (2)
• The frequency of calcium supplementation depends on the animal's diet, time of the year, and the stage of the tortoise. (3)
• A general recommendation from Simon Girling, a UK zoological veterinary surgeon (Pet Owner's Guide to the Tortoise, 2002), is to offer plain calcium daily. (3)
• Andy Highfield of Tortoise Trust (Promoting Proper Bone Development, 2003) recommends daily supplementation with phosphorus free, plain calcium. (3)
• Reptiles should have 1.3-8mg of calcium per Calorie of food being offered per day. (7)

Why I should supplement vitamin D to my tortoise, since I live in Finland? (Note: my tortoise spends his time outside only from May to August, and even then not every day. Inside he has a UV bulb in his indoor enclosure) Should I give him vitamin D orally? Is a UV bulb enough?

• As a general rule, if you live in an area where tortoises and turtles occur naturally and your animals are able to spend at least three or four hours outdoors in unfiltered sunlight daily, you probably do not need to rely upon oral D3 supplements. A calcium supplement alone should suffice. If you live in a northern, cloudy area where tortoises and turtles do not occur naturally, or your animals’ outdoor time is restricted, it is recommended that you do use a supplement on a regular basis. (1)
• In fact, genuine cases of primary vitamin deficiency (that it a deficiency caused by a lack of the vitamin in the diet rather than as a consequence of inability to metabolise the vitamin due to some other health problem) are quite rare. In the last 7 or 8 years we have encountered maybe 5 or 6 cases of primary vitamin deficiency in tortoises. In all of the cases we have seen, the base-line diet of the animals concerned was by any standards grossly inadequate and limited in range. There is virtually no chance of vitamin deficiencies occurring in tortoises which are fed on a well balanced, varied diet. (2)
• Vitamin D precursors can be present in food, or can be synthesised in the skin when it is exposed to ultraviolet sunlight. So maintaining levels of this vitamin should not be a problem for most wild tortoises which tend to live in arid, dry, environments with long sunshine hours. However, it is different when these animals are shipped and kept in colder climates, or if they are kept indoors out of direct sunlight*. For non-carnivores on a deficient ration, and not exposed to sufficient sunlight, vitamin D supplementation may be necessary. (2)
• There is evidence that artificial ultraviolet light sources may be ineffective at maintaining skin synthesis of vitamin D. (2)
• Vitamin D deficiency (true rickets) results in : Poor bone mineralisation with soft bendy bones or brittle bones that fracture easily and muscle tremors. (2)
• I cannot figure the dosage you get from the sun because there are far too many variables, but if your tortoise has free access to sunlight strong enough to give you a good tan, then you don't need to worry about this. If you live so far north that it is hard to tan in the winter, you may need to supplement with either UVB light or vitamins. (4)
• UVB light (from bulbs) is a HUGE question mark right now- what is the best way to offer general UVA for vision and behaviors, and UVB-295nm range for D3 fabrication? Heck if I know. I would suggest that if you are using UVB lighting in your set-up (and you should, for several reasons), then you may STILL want to offer some supplemental vitamin D at the lower dosage end. (4)
• Vitamin D is present in many foods, but be aware that some studies have suggested that dietary D does not work as well as 'solar D'- or maybe not at all. In any case, it probably does not do exactly the same thing as 'solar D' does. (4)
• There is no reason to be afraid to offer supplemental vitamin D to give our tortoises the best chances for success. (4)
• Research shows that D3 is also very important for immune function and is of benefit in auto-immune disease and as a preventative measure for cancer. (5)
• If you live in a northern, cloudy area where tortoises and turtles do not occur naturally, or your animals’ outdoor time is restricted, it is recommended that you do use a vitamin D supplement on a regular basis. (6)
• Vitamin and calcium supplements: Think of these as insurance- their purpose is to make sure the tortoises get everything they need even if the food we offer may be lacking in something. (7)
• Vitamin D deficiency usually occurs through poor diet and/or no provision of Ultraviolet lighting but can also be the result of an absence in parathyroid hormone secretion (hypoparathyroidism) due to damage to the parathyroid glands. A deficiency results in the development of MBD characterised by poor bone mineralisation with the development of soft bendy bones or brittle bones that fracture easily along with muscle tremors. This condition can be exacerbated by high phosphorus or low calcium in the animals diet e.g. lettuce/ celery/ cucumber for herbivores or meat only /day old mice/ chicks for carnivorous species. (8)

What happens if I give my tortoise too much vitamin D? How high is the risk?

• Oversupplementation can cause toxic side-effects and also affect the availability of other nutrients like Copper and Iodine. There is some evidence that reptiles may be inefficient at absorbing vitamin D from the gastrointestinal tract. In addition, excess supplementation must be avoided as this can lead to problems of excess calcification. (2)
• Products containing vitamin D3 should always be used very sparingly, if at all (use good quality UVB bulbs instead), because vitamin D3 can be dangerous if overdosed orally. (3)
• Instead of powdered vitamins and minerals, you can also use commercial tortoise foods as supplements. I rotate between powder supplements and commercial diets; I don't use them together. A little bit of everything to round out the diet. (3)
• You cannot overdose on vitamin D created by the sun or UVB lighting. While there are risks from too-strong UV on animals (skin cancer, eye damage, etc.), vitamin D overdose is not one of them! (4)
• Hypervitaminosis D3 occurs due to over supplementation (especially in reptiles who are also exposed to UV light) which leads to the calcification of soft tissues such as the wall of the arteries and kidneys creating hypertension and organ failure. Excess supplementation must be avoided as this too can lead to problems of calcification of the soft tissues. (8)

How much vitamin D should I supplement my tortoise with and how often? (Again, note: my tortoise spends his time outside only from May to August, and even then not every day. Inside he has a UV bulb in his indoor enclosure)

• The degree to which you may need to use a supplement containing vitamin D3 will vary according to several factors, principal among these being how far north you are situated, and the number of hours exposure to natural sunlight your animals receive or the type and intensity of UV-B supplemental lighting employed. (1)​
• We would suggest three times per week as an absolute minimum. If you provide high output UV-B lamps, and have adequate basking facilities, you may be able to rely upon these to promote adequate D3 synthesis but personally, I would prefer to hedge my bets by supplementing with a combined calcium and D3 supplement orally at least twice a week. (1)
• Do not dose with 'pure' vitamins unless under veterinary direction - some pure vitamins (such as vitamins A & D are highly toxic if taken in excess). These should only be used as part of a treatment program to correct a properly diagnosed specific deficiency. (2)
• The frequency of vitamin supplementation depends on the animal's diet, time of the year, and the stage of the tortoise. (3)
• Andy Highfield of Tortoise Trust (Promoting Proper Bone Development, 2003) recommendation for vitamin D3 varies. If your tortoises spend 3-4 hours outside daily and you live in an area that has wild tortoises, you probably do not need to supplement vitamin D3. Otherwise, provide a small amount of oral vitamin D3 about 2-3 times a week. (3)
• The target range for vitamin D is probably around 5-10 International Units (IU) per kilogram of tortoise a day. (4)
• For the dosing, I would aim for:
  - 7ish IU per kilogram (or, about 0.007ish IU per gram) per day for tortoises without supplemental UVB.
  - 5ish IU per kilogram (or, about 0.005ish per gram) per day for tortoises with UVB lighting.
  - no supplemental D for tortoises under natural sunlight, especially nearer the Equator.
  - The doses can be offered daily, every few days, or weekly, whatever is convenient as long as they get the dose they would have gotten if it was offered every day. (4)
• We would suggest three times per week as an absolute minimum. If you provide high output UV-B lamps and have adequate basking facilities, you may be able to rely upon these to promote adequate D3 synthesis but personally, I would prefer to hedge my bets by supplementing with calcium and D3 supplement orally at least twice a week. (6)
• Reptiles should get 10-20IU’s per kilogram of body weight a day. (7)

Other questions about vitamin D and calsium: Is six months per year enough? What supplements for vitamin D are safe? Does vitamin D supplementation even do anything without sun?

• Some vitamins are washed out of the body daily and need constant replenishment- B, C, K, etc. Vitamins A, D, and E are stored in the fat and used as needed. Since they are needed every day by a growing or active tortoise, we do not want the fat reserves to get too low, so need to help ensure an on-going dosage. (Note that the flip side of this is that the tortoise needs a healthy amount of body fat to store energy in as well! A good argument for making sure they get enough food.) Hibernating tortoises need to store enough vitamin D to withstand the winter, so it is very possible that at least some species can absorb enough from being outside to last the winter indoors. (I am not sure I would count on this for non-hibernating species.) (4)
• Let the buyer beware! Recent reports have said that many animal and reptile vitamins do not contain what the label says- even some ‘big name’ vitamin labels were found to be inaccurate- most often in regards to how much calcium is present. Some experts are recommending
  crushing human vitamins, which are more regulated, to ensure the proper nutrients. (7)
• Vitamin D supplementation may be necessary, however, there is evidence that some reptiles may be inefficient at absorbing vitamin D from the gastrointestinal tract. There is further evidence that artificial Ultra-Violet light sources may be ineffective at maintaining skin synthesis of vitamin D as different species have evolved to take advantage of different wavelengths and dispersal patterns of UV radiation depending on the environment the species originated from. UV lighting may also require replacing after 6 months (even if they are still working) as they may lose part of their spectrum. Furthermore, UV lighting requires correct positioning to allow for the correct intensity of UV lighting to reach the animal. It is important to note that a range of species-specific strategies are used to obtain adequate amounts of D3 for calcium homeostasis. It is important to know whether your species relies heavily on photo biosynthesis, dietary sources, a combination or has simply evolved to not require any supplemental D3. (8)

Sources list:
(1) https://www.tortoisetrust.org/articles/calcium.htm

(2) https://www.studbooks.eu/articles/all-about-vitamins-minerals-and-tortoises/

(3) https://startortoises.net/diet-supplements.html

(4) https://tortoiseforum.org/threads/vitamin-d-supplements-dosage-information.21330/ (The original post by Madkins007)

(5) https://www.russiantortoise.net/calcium.htm

(6) https://crazycrittersinc.com/what-are-the-calciumvitamin-and-mineral-needs-of-tortoises/

(7) https://tortoiselibrary.com/nutrition-2/nutrients/

(8) https://reptile-savvy.weebly.com/vitamin-d3.html

 

[The_Four_Toed_Edward]

I am worried whether my tortoise is going to get enough vitamin D here in Finland, so I did some research. Unfortunately the advice I found was conflicting, and as a new keeper I don’t know what advice is good and which sources to trust. So, I decided to turn to you with my questions and the answers I found. I will list under the question the answers I got with bullet points. The number in brackets coincides with the numbers listed down in my sources list.

So tell me, what answers would you give to my questions? Is the info I found correct? Are the sources I found good? I would love to hear your opinion and the arguments behind it.

What is the proper Ca? Why should I use calcium supplementation?

• It is usually advised that the Ca ratio of the total ration is between 1:1 and 2:1. (2)
• For tortoise diets, the traditional recommendation for calcium to phosphorus ratio (Ca) is 2:1 at the minimum. A ratio of 5:1, or higher, would be even better. (3)
• Based on newer studies, the need for calcium in tortoises may be even greater than previously thought. For example, a recent study done on plants eaten by Egyptian tortoises in the wild revealed that the mean Ca ratio was about 14:1. The Ca ratio ranged from 3.92 to 32.44 (The Batagur #2, TTPG, 2012).(3)
• The calcium-to-phosphorus ratio of captive diets is also typically far lower overall than is seen in the wild. Some typical examples include Plantago sp., with Ca ratios of above 20:1 and Opuntiasp., where Ca ratios can be as high as 78:1. (6)
• In order to make bones less brittle, we mix in some phosphorous for toughness, in a ratio of about three to four parts calcium to one part phosphorous. This is called the Calciumhosphorous Ratio, abbreviated Ca. A good Ca would be 2:1, a poor one would be 0.5:1. Too much phosphorus in relation to calcium and the bones get soft. (7)
• You can sprinkle some phosphorus free calcium carbonate powder on foods, especially if you use grocery store greens, to up the calcium content. (3)
• There is no reason to be afraid to offer supplemental calcium ato give our tortoises the best chances for success. (4)
• Calcium is essential for healthy blood and also helps to regulate heartbeat. (6)
• In addition, calcium assists in the process of blood clotting and prevent the accumulation of too much acid or too much alkali in the blood. It also plays a part in muscle growth, muscle contraction nerve transmission. (6)
• Calcium aids in the body’s utilization of iron helps activate several enzymes (catalysts important in metabolism) and helps regulate the passage of nutrients in and out of cell walls. (6)
• One problem in relying exclusively upon dietary selection is that many plants that on the surface appear to offer good, or positive calcium-to-phosphorus ratios, also contain chemicals that inhibit calcium take-up. (6)
• Vitamin and calcium supplements: Think of these as insurance- their purpose is to make sure the tortoises get everything they need even if the food we offer may be lacking in something. (7)

Why should I use reptical?

• Cuttlefish bone is a long-standing method of providing extra calcium to tortoises, and especially to turtles, as it floats readily in water. The main chemical constituents of cuttlebone are calcium carbonate, sodium chloride, calcium phosphate, magnesium salts and an abundance of micro-trace elements. Despite its high gross calcium content, cuttlefish bone is relatively poorly absorbed, and as such should not be relied upon as the sole source of calcium supplementation. It can, however, be employed as a secondary source. (1)
• On balance, the safest and most effective calcium supplements for routine use with captive tortoises would appear to be a calcium carbonate based, phosphorus-free ground calcium powder, preferably of commercial quality, either with or without added vitamin D3. (1)
• Reptical with D3- 13.7 IU per gram of powder (4)

What happens if my tortoise gets too much calcium? How high of a risk is there for that?

• In theory, excessively high intakes of calcium may interfere with the absorption of other nutrients such as iron and zinc, however, in chelonia we are not aware that such effects have been demonstrated. Other potential adverse effects of chronic intakes of high doses of calcium include Hypervitaminosis-D in the case of supplements containing both calcium and vitamin D. (1)
• Recent human studies indicate that increased intake of calcium does not increase risk of kidney stones. However, restricting dietary calcium may increase urinary excretion of oxalate which in turn increases risk of kidney stones in addition to causing bone developmental problems. (1)
• The indiscriminate use of mineral supplements is a highly dangerous practice for several reasons: If the base ration already contains sufficient mineral content excessive supplementation may result in toxic levels or mineral imbalances. Metabolic bone disease can result from excessive mineral intake as well as deficiency. (2)
• High amounts of calcium in the form of mineral supplements may not be digested and used by the animal, and this calcium can pass through the digestive tract and interfere with the availability of other minerals (eg copper, iron, zinc) in the ration by : Competing for receptor sites in the gastrointestinal tract and Binding with other minerals making them unavailable to the animal. (2)
• It is generally known that too much calcium results in secondary deficiencies of zinc, copper and iodine, mal-absorption of essential fatty acids, and formation of calcium-containing bladder stones. (5)
• In theory, excessively high intakes of calcium may interfere with the absorption of other nutrients such as iron and zinc, however, in we are not aware that such effects have been demonstrated. Other potential adverse effects of chronic intakes of high doses of calcium include Hypervitaminosis-D. (6)

How much calcium should I give my tortoise and how often?

• If mineral supplements have to be given to avoid deficiency disease because the base ration is inadequate, they should be used sparingly and with caution. (2)
• The frequency of calcium supplementation depends on the animal's diet, time of the year, and the stage of the tortoise. (3)
• A general recommendation from Simon Girling, a UK zoological veterinary surgeon (Pet Owner's Guide to the Tortoise, 2002), is to offer plain calcium daily. (3)
• Andy Highfield of Tortoise Trust (Promoting Proper Bone Development, 2003) recommends daily supplementation with phosphorus free, plain calcium. (3)
• Reptiles should have 1.3-8mg of calcium per Calorie of food being offered per day. (7)

Why I should supplement vitamin D to my tortoise, since I live in Finland? (Note: my tortoise spends his time outside only from May to August, and even then not every day. Inside he has a UV bulb in his indoor enclosure) Should I give him vitamin D orally? Is a UV bulb enough?

• As a general rule, if you live in an area where tortoises and turtles occur naturally and your animals are able to spend at least three or four hours outdoors in unfiltered sunlight daily, you probably do not need to rely upon oral D3 supplements. A calcium supplement alone should suffice. If you live in a northern, cloudy area where tortoises and turtles do not occur naturally, or your animals’ outdoor time is restricted, it is recommended that you do use a supplement on a regular basis. (1)
• In fact, genuine cases of primary vitamin deficiency (that it a deficiency caused by a lack of the vitamin in the diet rather than as a consequence of inability to metabolise the vitamin due to some other health problem) are quite rare. In the last 7 or 8 years we have encountered maybe 5 or 6 cases of primary vitamin deficiency in tortoises. In all of the cases we have seen, the base-line diet of the animals concerned was by any standards grossly inadequate and limited in range. There is virtually no chance of vitamin deficiencies occurring in tortoises which are fed on a well balanced, varied diet. (2)
• Vitamin D precursors can be present in food, or can be synthesised in the skin when it is exposed to ultraviolet sunlight. So maintaining levels of this vitamin should not be a problem for most wild tortoises which tend to live in arid, dry, environments with long sunshine hours. However, it is different when these animals are shipped and kept in colder climates, or if they are kept indoors out of direct sunlight*. For non-carnivores on a deficient ration, and not exposed to sufficient sunlight, vitamin D supplementation may be necessary. (2)
• There is evidence that artificial ultraviolet light sources may be ineffective at maintaining skin synthesis of vitamin D. (2)
• Vitamin D deficiency (true rickets) results in : Poor bone mineralisation with soft bendy bones or brittle bones that fracture easily and muscle tremors. (2)
• I cannot figure the dosage you get from the sun because there are far too many variables, but if your tortoise has free access to sunlight strong enough to give you a good tan, then you don't need to worry about this. If you live so far north that it is hard to tan in the winter, you may need to supplement with either UVB light or vitamins. (4)
• UVB light (from bulbs) is a HUGE question mark right now- what is the best way to offer general UVA for vision and behaviors, and UVB-295nm range for D3 fabrication? Heck if I know. I would suggest that if you are using UVB lighting in your set-up (and you should, for several reasons), then you may STILL want to offer some supplemental vitamin D at the lower dosage end. (4)
• Vitamin D is present in many foods, but be aware that some studies have suggested that dietary D does not work as well as 'solar D'- or maybe not at all. In any case, it probably does not do exactly the same thing as 'solar D' does. (4)
• There is no reason to be afraid to offer supplemental vitamin D to give our tortoises the best chances for success. (4)
• Research shows that D3 is also very important for immune function and is of benefit in auto-immune disease and as a preventative measure for cancer. (5)
• If you live in a northern, cloudy area where tortoises and turtles do not occur naturally, or your animals’ outdoor time is restricted, it is recommended that you do use a vitamin D supplement on a regular basis. (6)
• Vitamin and calcium supplements: Think of these as insurance- their purpose is to make sure the tortoises get everything they need even if the food we offer may be lacking in something. (7)
• Vitamin D deficiency usually occurs through poor diet and/or no provision of Ultraviolet lighting but can also be the result of an absence in parathyroid hormone secretion (hypoparathyroidism) due to damage to the parathyroid glands. A deficiency results in the development of MBD characterised by poor bone mineralisation with the development of soft bendy bones or brittle bones that fracture easily along with muscle tremors. This condition can be exacerbated by high phosphorus or low calcium in the animals diet e.g. lettuce/ celery/ cucumber for herbivores or meat only /day old mice/ chicks for carnivorous species. (8)

What happens if I give my tortoise too much vitamin D? How high is the risk?

• Oversupplementation can cause toxic side-effects and also affect the availability of other nutrients like Copper and Iodine. There is some evidence that reptiles may be inefficient at absorbing vitamin D from the gastrointestinal tract. In addition, excess supplementation must be avoided as this can lead to problems of excess calcification. (2)
• Products containing vitamin D3 should always be used very sparingly, if at all (use good quality UVB bulbs instead), because vitamin D3 can be dangerous if overdosed orally. (3)
• Instead of powdered vitamins and minerals, you can also use commercial tortoise foods as supplements. I rotate between powder supplements and commercial diets; I don't use them together. A little bit of everything to round out the diet. (3)
• You cannot overdose on vitamin D created by the sun or UVB lighting. While there are risks from too-strong UV on animals (skin cancer, eye damage, etc.), vitamin D overdose is not one of them! (4)
• Hypervitaminosis D3 occurs due to over supplementation (especially in reptiles who are also exposed to UV light) which leads to the calcification of soft tissues such as the wall of the arteries and kidneys creating hypertension and organ failure. Excess supplementation must be avoided as this too can lead to problems of calcification of the soft tissues. (8)

How much vitamin D should I supplement my tortoise with and how often? (Again, note: my tortoise spends his time outside only from May to August, and even then not every day. Inside he has a UV bulb in his indoor enclosure)

• The degree to which you may need to use a supplement containing vitamin D3 will vary according to several factors, principal among these being how far north you are situated, and the number of hours exposure to natural sunlight your animals receive or the type and intensity of UV-B supplemental lighting employed. (1)​
• We would suggest three times per week as an absolute minimum. If you provide high output UV-B lamps, and have adequate basking facilities, you may be able to rely upon these to promote adequate D3 synthesis but personally, I would prefer to hedge my bets by supplementing with a combined calcium and D3 supplement orally at least twice a week. (1)
• Do not dose with 'pure' vitamins unless under veterinary direction - some pure vitamins (such as vitamins A & D are highly toxic if taken in excess). These should only be used as part of a treatment program to correct a properly diagnosed specific deficiency. (2)
• The frequency of vitamin supplementation depends on the animal's diet, time of the year, and the stage of the tortoise. (3)
• Andy Highfield of Tortoise Trust (Promoting Proper Bone Development, 2003) recommendation for vitamin D3 varies. If your tortoises spend 3-4 hours outside daily and you live in an area that has wild tortoises, you probably do not need to supplement vitamin D3. Otherwise, provide a small amount of oral vitamin D3 about 2-3 times a week. (3)
• The target range for vitamin D is probably around 5-10 International Units (IU) per kilogram of tortoise a day. (4)
• For the dosing, I would aim for:
  - 7ish IU per kilogram (or, about 0.007ish IU per gram) per day for tortoises without supplemental UVB.
  - 5ish IU per kilogram (or, about 0.005ish per gram) per day for tortoises with UVB lighting.
  - no supplemental D for tortoises under natural sunlight, especially nearer the Equator.
  - The doses can be offered daily, every few days, or weekly, whatever is convenient as long as they get the dose they would have gotten if it was offered every day. (4)
• We would suggest three times per week as an absolute minimum. If you provide high output UV-B lamps and have adequate basking facilities, you may be able to rely upon these to promote adequate D3 synthesis but personally, I would prefer to hedge my bets by supplementing with calcium and D3 supplement orally at least twice a week. (6)
• Reptiles should get 10-20IU’s per kilogram of body weight a day. (7)

Other questions about vitamin D and calsium: Is six months per year enough? What supplements for vitamin D are safe? Does vitamin D supplementation even do anything without sun?

• Some vitamins are washed out of the body daily and need constant replenishment- B, C, K, etc. Vitamins A, D, and E are stored in the fat and used as needed. Since they are needed every day by a growing or active tortoise, we do not want the fat reserves to get too low, so need to help ensure an on-going dosage. (Note that the flip side of this is that the tortoise needs a healthy amount of body fat to store energy in as well! A good argument for making sure they get enough food.) Hibernating tortoises need to store enough vitamin D to withstand the winter, so it is very possible that at least some species can absorb enough from being outside to last the winter indoors. (I am not sure I would count on this for non-hibernating species.) (4)
• Let the buyer beware! Recent reports have said that many animal and reptile vitamins do not contain what the label says- even some ‘big name’ vitamin labels were found to be inaccurate- most often in regards to how much calcium is present. Some experts are recommending
  crushing human vitamins, which are more regulated, to ensure the proper nutrients. (7)
• Vitamin D supplementation may be necessary, however, there is evidence that some reptiles may be inefficient at absorbing vitamin D from the gastrointestinal tract. There is further evidence that artificial Ultra-Violet light sources may be ineffective at maintaining skin synthesis of vitamin D as different species have evolved to take advantage of different wavelengths and dispersal patterns of UV radiation depending on the environment the species originated from. UV lighting may also require replacing after 6 months (even if they are still working) as they may lose part of their spectrum. Furthermore, UV lighting requires correct positioning to allow for the correct intensity of UV lighting to reach the animal. It is important to note that a range of species-specific strategies are used to obtain adequate amounts of D3 for calcium homeostasis. It is important to know whether your species relies heavily on photo biosynthesis, dietary sources, a combination or has simply evolved to not require any supplemental D3. (8)

Sources list:
(1) https://www.tortoisetrust.org/articles/calcium.htm

(2) https://www.studbooks.eu/articles/all-about-vitamins-minerals-and-tortoises/

(3) https://startortoises.net/diet-supplements.html

(4) https://tortoiseforum.org/threads/vitamin-d-supplements-dosage-information.21330/ (The original post by Madkins007)

(5) https://www.russiantortoise.net/calcium.htm

(6) https://crazycrittersinc.com/what-are-the-calciumvitamin-and-mineral-needs-of-tortoises/

(7) https://tortoiselibrary.com/nutrition-2/nutrients/

(8) https://reptile-savvy.weebly.com/vitamin-d3.html

I didn't realize writing the post that if I wrote Ca : P all together it would turn into this Ca Sorry for the inconvenience reading this post!

 

[ZEROPILOT]

Correct diet and a correct type of uvb light will provide the vitamin D.
Does your tortoise get outdoors sunlight?
Do you have a T5 HO linear strip florescent UVB tube?
What is the diet?
We usually only use calcium/mineral supplements for baby tortoises. Adults generally get what they need from diet and sunlight. (Actual or artificial)

 

[jaizei]

I didn't realize writing the post that if I wrote Ca : P all together it would turn into this Ca Sorry for the inconvenience reading this post!

I went through an added a space between colon and p. You can also use the icode tag to overide the auto-smilies like this: Ca:p

 

[The_Four_Toed_Edward]

I went through an added a space between colon and p. You can also use the icode tag to overide the auto-smilies like this: Ca:p

Thanks, I am still a new member on the forum, so I didn't realice it before posting!

 

[The_Four_Toed_Edward]

Correct diet and a correct type of uvb light will provide the vitamin D.
Does your tortoise get outdoors sunlight?
Do you have a T5 HO linear strip florescent UVB tube?
What is the diet?
We usually only use calcium/mineral supplements for baby tortoises. Adults generally get what they need from diet and sunlight. (Actual or artificial)

My tortoise gets outdoor sunlight only from May to August, and even then not everyday beacuse the weather here in Finland doesn't really permit that. Plus there aren't any native turtles and tortoises here in Finland. I am also worried, beacause humans produce D3 only when UVI is at least 3, but that happens here in northern Finland only on a cloudless day in the middle of summer, for a maxium of 7 hours per day. That's why it is recommended for 0-17 year olds, pregnant women and over 70 year olds to take supplementary vitamin D every day around the year. As for adults aged 17 to 70 supplementary vitamin D is recomended in the winter months.

He has a lucky reptile led sun flood in 18w. I am looking into getting a T5 HO linear strip florescent UVB tube or something similar in a bulb form.

There is still a lot of snow outside, so this is his current diet and what he has been eating in the winter:

Different types of lettuces, also low in nutritional value: (iceberg lettuce, endive and romaine lettuce). Fruits and vegetables with high sugar content: (bell pepper, fennel, carrot and turnip). Types of cabbage: (Broccoli, cauli flower, asparagus, tenderstem broccoli, rucola, cabbage, napa cabbage, brussels sprout, leaf cabbage, red cabbage and bok choi). Fresh herbs: (Basilica, coriander, dill, mint, thyme, salvia, lemon balm, rosemary, oregano, tarragon, lovage and lemongrass). Occasionally some other vegetables like spinach, celery, sorrel, globe artichoke, cucumber, zucchini, eggplant, squash, pumpkin and radish.

With his food I strive for variety. As a supplement to add fiber he gets soaked Agrobs Testudo Herbs and some rabbit hay pellets (I am trying to finish the bag) four times a week. He is going to be eating mainly wild weeds in the summer.In the summer I think he isn't going to be needing the supplementation?

He is currently getting the repticalc calcium powder once a week, since I want to make sure his diet has the right Calcium to Phosphorus ratio. I thought this wouldn't do any harm, especially as the plants I feed him now aren't ideal. What do you think about the claims of artificial UV and vitamin D not being enough?

 

[Littleredfootbigredheart]

He has a lucky reptile led sun flood in 18w. I am looking into getting a T5 HO linear strip florescent UVB tube or something similar in a bulb form.

I’ll leave it to the more experienced members to answer your other queries.
But it’s definitely recommended to go with the t5 strips, ideally mounted into a reflector, the bulb versions are notorious for not giving out enough uv, the strips will cover a much larger surface area within your enclosure🙂

 

[ZEROPILOT]

Don't use any "bulb" type uvb source.

 

[Tom]

Way too much to read. I got through about half of it, and it was mostly good info. You are overthinking this tremendously. Just give a little pinch of calcium with D3 a couple of times a week and you will be good.

The reason there is so much info on this is because all of it works, and that is because there is a wide margin of error. If you give no calcium at all the tortoise will be fine. If you give calcium every day the tortoise will be fine. Here are some general guidelines:
1. If feeding the correct diet of a wide variety of broadleaf weeds, no calcium supplementation is necessary.
2. If feeding a lot of grocery store greens and lettuce, a small pinch two or three times a week is all that is needed and will meet the tortoise's needs.
3. Growing babies and egg laying females can benefit from a little bit more calcium supplementation, while fully grown adult males really don't need much calcium supplementation.
4. The low amount of D3 in most supplements is not enough to overdose when used normally. People nearer to the equator whose tortoises get a good diet and lots of sunshine really do not need any D3 supplementation. People who live in the north of Finland should probably use a supplement with D3 in it.

 

[Alex and the Redfoot]

I am worried whether my tortoise is going to get enough vitamin D here in Finland, so I did some research. Unfortunately the advice I found was conflicting, and as a new keeper I don’t know what advice is good and which sources to trust. So, I decided to turn to you with my questions and the answers I found. I will list under the question the answers I got with bullet points. The number in brackets coincides with the numbers listed down in my sources list.

So tell me, what answers would you give to my questions? Is the info I found correct? Are the sources I found good? I would love to hear your opinion and the arguments behind it.

What is the proper Ca: P? Why should I use calcium supplementation?

• It is usually advised that the Ca: P ratio of the total ration is between 1:1 and 2:1. (2)
• For tortoise diets, the traditional recommendation for calcium to phosphorus ratio (Ca: P) is 2:1 at the minimum. A ratio of 5:1, or higher, would be even better. (3)
• Based on newer studies, the need for calcium in tortoises may be even greater than previously thought. For example, a recent study done on plants eaten by Egyptian tortoises in the wild revealed that the mean Ca: P ratio was about 14:1. The Ca: P ratio ranged from 3.92 to 32.44 (The Batagur #2, TTPG, 2012).(3)
• The calcium-to-phosphorus ratio of captive diets is also typically far lower overall than is seen in the wild. Some typical examples include Plantago sp., with Ca: P ratios of above 20:1 and Opuntia sp., where Ca: P ratios can be as high as 78:1. (6)
• In order to make bones less brittle, we mix in some phosphorous for toughness, in a ratio of about three to four parts calcium to one part phosphorous. This is called the Calcium: Phosphorous Ratio, abbreviated Ca: P. A good Ca: P would be 2:1, a poor one would be 0.5:1. Too much phosphorus in relation to calcium and the bones get soft. (7)
• You can sprinkle some phosphorus free calcium carbonate powder on foods, especially if you use grocery store greens, to up the calcium content. (3)
• There is no reason to be afraid to offer supplemental calcium ato give our tortoises the best chances for success. (4)
• Calcium is essential for healthy blood and also helps to regulate heartbeat. (6)
• In addition, calcium assists in the process of blood clotting and prevent the accumulation of too much acid or too much alkali in the blood. It also plays a part in muscle growth, muscle contraction nerve transmission. (6)
• Calcium aids in the body’s utilization of iron helps activate several enzymes (catalysts important in metabolism) and helps regulate the passage of nutrients in and out of cell walls. (6)
• One problem in relying exclusively upon dietary selection is that many plants that on the surface appear to offer good, or positive calcium-to-phosphorus ratios, also contain chemicals that inhibit calcium take-up. (6)
• Vitamin and calcium supplements: Think of these as insurance- their purpose is to make sure the tortoises get everything they need even if the food we offer may be lacking in something. (7)

Why should I use reptical?

• Cuttlefish bone is a long-standing method of providing extra calcium to tortoises, and especially to turtles, as it floats readily in water. The main chemical constituents of cuttlebone are calcium carbonate, sodium chloride, calcium phosphate, magnesium salts and an abundance of micro-trace elements. Despite its high gross calcium content, cuttlefish bone is relatively poorly absorbed, and as such should not be relied upon as the sole source of calcium supplementation. It can, however, be employed as a secondary source. (1)
• On balance, the safest and most effective calcium supplements for routine use with captive tortoises would appear to be a calcium carbonate based, phosphorus-free ground calcium powder, preferably of commercial quality, either with or without added vitamin D3. (1)
• Reptical with D3- 13.7 IU per gram of powder (4)

What happens if my tortoise gets too much calcium? How high of a risk is there for that?

• In theory, excessively high intakes of calcium may interfere with the absorption of other nutrients such as iron and zinc, however, in chelonia we are not aware that such effects have been demonstrated. Other potential adverse effects of chronic intakes of high doses of calcium include Hypervitaminosis-D in the case of supplements containing both calcium and vitamin D. (1)
• Recent human studies indicate that increased intake of calcium does not increase risk of kidney stones. However, restricting dietary calcium may increase urinary excretion of oxalate which in turn increases risk of kidney stones in addition to causing bone developmental problems. (1)
• The indiscriminate use of mineral supplements is a highly dangerous practice for several reasons: If the base ration already contains sufficient mineral content excessive supplementation may result in toxic levels or mineral imbalances. Metabolic bone disease can result from excessive mineral intake as well as deficiency. (2)
• High amounts of calcium in the form of mineral supplements may not be digested and used by the animal, and this calcium can pass through the digestive tract and interfere with the availability of other minerals (eg copper, iron, zinc) in the ration by : Competing for receptor sites in the gastrointestinal tract and Binding with other minerals making them unavailable to the animal. (2)
• It is generally known that too much calcium results in secondary deficiencies of zinc, copper and iodine, mal-absorption of essential fatty acids, and formation of calcium-containing bladder stones. (5)
• In theory, excessively high intakes of calcium may interfere with the absorption of other nutrients such as iron and zinc, however, in we are not aware that such effects have been demonstrated. Other potential adverse effects of chronic intakes of high doses of calcium include Hypervitaminosis-D. (6)

How much calcium should I give my tortoise and how often?

• If mineral supplements have to be given to avoid deficiency disease because the base ration is inadequate, they should be used sparingly and with caution. (2)
• The frequency of calcium supplementation depends on the animal's diet, time of the year, and the stage of the tortoise. (3)
• A general recommendation from Simon Girling, a UK zoological veterinary surgeon (Pet Owner's Guide to the Tortoise, 2002), is to offer plain calcium daily. (3)
• Andy Highfield of Tortoise Trust (Promoting Proper Bone Development, 2003) recommends daily supplementation with phosphorus free, plain calcium. (3)
• Reptiles should have 1.3-8mg of calcium per Calorie of food being offered per day. (7)

Why I should supplement vitamin D to my tortoise, since I live in Finland? (Note: my tortoise spends his time outside only from May to August, and even then not every day. Inside he has a UV bulb in his indoor enclosure) Should I give him vitamin D orally? Is a UV bulb enough?

• As a general rule, if you live in an area where tortoises and turtles occur naturally and your animals are able to spend at least three or four hours outdoors in unfiltered sunlight daily, you probably do not need to rely upon oral D3 supplements. A calcium supplement alone should suffice. If you live in a northern, cloudy area where tortoises and turtles do not occur naturally, or your animals’ outdoor time is restricted, it is recommended that you do use a supplement on a regular basis. (1)
• In fact, genuine cases of primary vitamin deficiency (that it a deficiency caused by a lack of the vitamin in the diet rather than as a consequence of inability to metabolise the vitamin due to some other health problem) are quite rare. In the last 7 or 8 years we have encountered maybe 5 or 6 cases of primary vitamin deficiency in tortoises. In all of the cases we have seen, the base-line diet of the animals concerned was by any standards grossly inadequate and limited in range. There is virtually no chance of vitamin deficiencies occurring in tortoises which are fed on a well balanced, varied diet. (2)
• Vitamin D precursors can be present in food, or can be synthesised in the skin when it is exposed to ultraviolet sunlight. So maintaining levels of this vitamin should not be a problem for most wild tortoises which tend to live in arid, dry, environments with long sunshine hours. However, it is different when these animals are shipped and kept in colder climates, or if they are kept indoors out of direct sunlight*. For non-carnivores on a deficient ration, and not exposed to sufficient sunlight, vitamin D supplementation may be necessary. (2)
• There is evidence that artificial ultraviolet light sources may be ineffective at maintaining skin synthesis of vitamin D. (2)
• Vitamin D deficiency (true rickets) results in : Poor bone mineralisation with soft bendy bones or brittle bones that fracture easily and muscle tremors. (2)
• I cannot figure the dosage you get from the sun because there are far too many variables, but if your tortoise has free access to sunlight strong enough to give you a good tan, then you don't need to worry about this. If you live so far north that it is hard to tan in the winter, you may need to supplement with either UVB light or vitamins. (4)
• UVB light (from bulbs) is a HUGE question mark right now- what is the best way to offer general UVA for vision and behaviors, and UVB-295nm range for D3 fabrication? Heck if I know. I would suggest that if you are using UVB lighting in your set-up (and you should, for several reasons), then you may STILL want to offer some supplemental vitamin D at the lower dosage end. (4)
• Vitamin D is present in many foods, but be aware that some studies have suggested that dietary D does not work as well as 'solar D'- or maybe not at all. In any case, it probably does not do exactly the same thing as 'solar D' does. (4)
• There is no reason to be afraid to offer supplemental vitamin D to give our tortoises the best chances for success. (4)
• Research shows that D3 is also very important for immune function and is of benefit in auto-immune disease and as a preventative measure for cancer. (5)
• If you live in a northern, cloudy area where tortoises and turtles do not occur naturally, or your animals’ outdoor time is restricted, it is recommended that you do use a vitamin D supplement on a regular basis. (6)
• Vitamin and calcium supplements: Think of these as insurance- their purpose is to make sure the tortoises get everything they need even if the food we offer may be lacking in something. (7)
• Vitamin D deficiency usually occurs through poor diet and/or no provision of Ultraviolet lighting but can also be the result of an absence in parathyroid hormone secretion (hypoparathyroidism) due to damage to the parathyroid glands. A deficiency results in the development of MBD characterised by poor bone mineralisation with the development of soft bendy bones or brittle bones that fracture easily along with muscle tremors. This condition can be exacerbated by high phosphorus or low calcium in the animals diet e.g. lettuce/ celery/ cucumber for herbivores or meat only /day old mice/ chicks for carnivorous species. (8)

What happens if I give my tortoise too much vitamin D? How high is the risk?

• Oversupplementation can cause toxic side-effects and also affect the availability of other nutrients like Copper and Iodine. There is some evidence that reptiles may be inefficient at absorbing vitamin D from the gastrointestinal tract. In addition, excess supplementation must be avoided as this can lead to problems of excess calcification. (2)
• Products containing vitamin D3 should always be used very sparingly, if at all (use good quality UVB bulbs instead), because vitamin D3 can be dangerous if overdosed orally. (3)
• Instead of powdered vitamins and minerals, you can also use commercial tortoise foods as supplements. I rotate between powder supplements and commercial diets; I don't use them together. A little bit of everything to round out the diet. (3)
• You cannot overdose on vitamin D created by the sun or UVB lighting. While there are risks from too-strong UV on animals (skin cancer, eye damage, etc.), vitamin D overdose is not one of them! (4)
• Hypervitaminosis D3 occurs due to over supplementation (especially in reptiles who are also exposed to UV light) which leads to the calcification of soft tissues such as the wall of the arteries and kidneys creating hypertension and organ failure. Excess supplementation must be avoided as this too can lead to problems of calcification of the soft tissues. (8)

How much vitamin D should I supplement my tortoise with and how often? (Again, note: my tortoise spends his time outside only from May to August, and even then not every day. Inside he has a UV bulb in his indoor enclosure)

• The degree to which you may need to use a supplement containing vitamin D3 will vary according to several factors, principal among these being how far north you are situated, and the number of hours exposure to natural sunlight your animals receive or the type and intensity of UV-B supplemental lighting employed. (1)​
• We would suggest three times per week as an absolute minimum. If you provide high output UV-B lamps, and have adequate basking facilities, you may be able to rely upon these to promote adequate D3 synthesis but personally, I would prefer to hedge my bets by supplementing with a combined calcium and D3 supplement orally at least twice a week. (1)
• Do not dose with 'pure' vitamins unless under veterinary direction - some pure vitamins (such as vitamins A & D are highly toxic if taken in excess). These should only be used as part of a treatment program to correct a properly diagnosed specific deficiency. (2)
• The frequency of vitamin supplementation depends on the animal's diet, time of the year, and the stage of the tortoise. (3)
• Andy Highfield of Tortoise Trust (Promoting Proper Bone Development, 2003) recommendation for vitamin D3 varies. If your tortoises spend 3-4 hours outside daily and you live in an area that has wild tortoises, you probably do not need to supplement vitamin D3. Otherwise, provide a small amount of oral vitamin D3 about 2-3 times a week. (3)
• The target range for vitamin D is probably around 5-10 International Units (IU) per kilogram of tortoise a day. (4)
• For the dosing, I would aim for:
  - 7ish IU per kilogram (or, about 0.007ish IU per gram) per day for tortoises without supplemental UVB.
  - 5ish IU per kilogram (or, about 0.005ish per gram) per day for tortoises with UVB lighting.
  - no supplemental D for tortoises under natural sunlight, especially nearer the Equator.
  - The doses can be offered daily, every few days, or weekly, whatever is convenient as long as they get the dose they would have gotten if it was offered every day. (4)
• We would suggest three times per week as an absolute minimum. If you provide high output UV-B lamps and have adequate basking facilities, you may be able to rely upon these to promote adequate D3 synthesis but personally, I would prefer to hedge my bets by supplementing with calcium and D3 supplement orally at least twice a week. (6)
• Reptiles should get 10-20IU’s per kilogram of body weight a day. (7)

Other questions about vitamin D and calsium: Is six months per year enough? What supplements for vitamin D are safe? Does vitamin D supplementation even do anything without sun?

• Some vitamins are washed out of the body daily and need constant replenishment- B, C, K, etc. Vitamins A, D, and E are stored in the fat and used as needed. Since they are needed every day by a growing or active tortoise, we do not want the fat reserves to get too low, so need to help ensure an on-going dosage. (Note that the flip side of this is that the tortoise needs a healthy amount of body fat to store energy in as well! A good argument for making sure they get enough food.) Hibernating tortoises need to store enough vitamin D to withstand the winter, so it is very possible that at least some species can absorb enough from being outside to last the winter indoors. (I am not sure I would count on this for non-hibernating species.) (4)
• Let the buyer beware! Recent reports have said that many animal and reptile vitamins do not contain what the label says- even some ‘big name’ vitamin labels were found to be inaccurate- most often in regards to how much calcium is present. Some experts are recommending
  crushing human vitamins, which are more regulated, to ensure the proper nutrients. (7)
• Vitamin D supplementation may be necessary, however, there is evidence that some reptiles may be inefficient at absorbing vitamin D from the gastrointestinal tract. There is further evidence that artificial Ultra-Violet light sources may be ineffective at maintaining skin synthesis of vitamin D as different species have evolved to take advantage of different wavelengths and dispersal patterns of UV radiation depending on the environment the species originated from. UV lighting may also require replacing after 6 months (even if they are still working) as they may lose part of their spectrum. Furthermore, UV lighting requires correct positioning to allow for the correct intensity of UV lighting to reach the animal. It is important to note that a range of species-specific strategies are used to obtain adequate amounts of D3 for calcium homeostasis. It is important to know whether your species relies heavily on photo biosynthesis, dietary sources, a combination or has simply evolved to not require any supplemental D3. (8)

Sources list:
(1) https://www.tortoisetrust.org/articles/calcium.htm

(2) https://www.studbooks.eu/articles/all-about-vitamins-minerals-and-tortoises/

(3) https://startortoises.net/diet-supplements.html

(4) https://tortoiseforum.org/threads/vitamin-d-supplements-dosage-information.21330/ (The original post by Madkins007)

(5) https://www.russiantortoise.net/calcium.htm

(6) https://crazycrittersinc.com/what-are-the-calciumvitamin-and-mineral-needs-of-tortoises/

(7) https://tortoiselibrary.com/nutrition-2/nutrients/

(8) https://reptile-savvy.weebly.com/vitamin-d3.html

Thank you for that post! Great to see this information compiled in one place.

I wish I can find references to papers where artificial UVB light was proven to be ineffective. Likely, it was true a while ago with older type lamps (T8 or T12).

Also, I'm still confused by D3 oral supplementation: if D3 is poorly absorbed from gastrointestinal tract how can we overdose it? Maybe only by providing huge exccess (like human D3 drops or shots).

And some nice additions to your collection of reading materials (thanks to jaizei for sharing these):
http://www.uvguide.co.uk/index.htm (old but still useful, now all discussions have moved to a Facebook group)
https://www.licht-im-terrarium.de/ - a good source of information on reptile lightning

 

[The_Four_Toed_Edward]

Way too much to read. I got through about half of it, and it was mostly good info. You are overthinking this tremendously. Just give a little pinch of calcium with D3 a couple of times a week and you will be good.

The reason there is so much info on this is because all of it works, and that is because there is a wide margin of error. If you give no calcium at all the tortoise will be fine. If you give calcium every day the tortoise will be fine. Here are some general guidelines:
1. If feeding the correct diet of a wide variety of broadleaf weeds, no calcium supplementation is necessary.
2. If feeding a lot of grocery store greens and lettuce, a small pinch two or three times a week is all that is needed and will meet the tortoise's needs.
3. Growing babies and egg laying females can benefit from a little bit more calcium supplementation, while fully grown adult males really don't need much calcium supplementation.
4. The low amount of D3 in most supplements is not enough to overdose when used normally. People nearer to the equator whose tortoises get a good diet and lots of sunshine really do not need any D3 supplementation. People who live in the north of Finland should probably use a supplement with D3 in it.

Thank you for your advice! I will be using the repticalc with D3 2-3 times a week during the colder months, since he is now eating grocery store greens.

You are right, I am probably overthinking it. I just got a bit scared from all the articles stating how dangerous it is to overdose on calcium and especially D3 if given orally. You are probably right, that I am on the safe side with those things

 

[The_Four_Toed_Edward]

I wish I can find references to papers where artificial UVB light was proven to be ineffective. Likely, it was true a while ago with older type lamps (T8 or T12).

Yeah, as you can see a lot of those reverences are old. I will also try to find the original references that people were talking about on those websites. It would be interesting to know what kind of lamps were used.

 

[The_Four_Toed_Edward]

Also, I'm still confused by D3 oral supplementation: if D3 is poorly absorbed from gastrointestinal tract how can we overdose it? Maybe only by providing huge exccess (like human D3 drops or shots).

As for this, I was wondering that too. Hence the title "conflicting advice". Some sources were warning about overdosing, some were saying tortoises can't get any use out of D3 given orally, go and figure...

 

[The_Four_Toed_Edward]

I wish I can find references to papers where artificial UVB light was proven to be ineffective. Likely, it was true a while ago with older type lamps (T8 or T12).

I wasn't able to find the resources referenced in those articles, but I found one study that might be the kind they are referencing with a quick search on google scholar: https://avmajournals.avma.org/view/journals/ajvr/73/11/ajvr.73.11.1781.xml

This experiment was done using a self-ballasted mercury-vapor lamp and a fluorescent UVB-emitting lamp. These were compared to a group of tortoises that were exposed to sunlight in an outdoor enclosure located in the natural geographic range of Hermann's tortoises.

Basically the result was that the mean ± SD plasma 25-hydroxyvitamin D3 concentrations for tortoises exposed to the mercury-vapor and fluorescent lamps were significantly lower on day 35 than they were on day 0, while the mean ± SD plasma 25-hydroxyvitamin D3 concentration for tortoises exposed to sunlight did not differ significantly between days 0. Mean day 35 plasma 25-hydroxyvitamin D3 concentration was significantly higher for tortoises exposed to sunlight versus those exposed to mercury-vapor or fluorescent lamps. Sunlight provided significantly more UVB radiation than did the mercury-vapor or fluorescent lamps.

These results aren't of course conclusive, but it just goes to show how much of the info we can't be 100% sure of yet. So, it is clear why there is so much conflicting advice

 

[Alex and the Redfoot]

As for this, I was wondering that too. Hence the title "conflicting advice". Some sources were warning about overdosing, some were saying tortoises can't get any use out of D3 given orally, go and figure...

Human D3 drops has 400U in one drop. So I think I know how to overdose...

 

[The_Four_Toed_Edward]

Human D3 drops has 400U in one drop. So I think I know how to overdose...

Yeah, it is easy to overdose when doing the supplementation wrong... Maybe I shouldn't take the overdosing warning all too seriously, considering the amount I am giving my tortoise (a pinch of repticalc with D3, 2 to 3 times a week).

 

[The_Four_Toed_Edward]

I wasn't able to find the resources referenced in those articles, but I found one study that might be the kind they are referencing with a quick search on google scholar: https://avmajournals.avma.org/view/journals/ajvr/73/11/ajvr.73.11.1781.xml

This experiment was done using a self-ballasted mercury-vapor lamp and a fluorescent UVB-emitting lamp. These were compared to a group of tortoises that were exposed to sunlight in an outdoor enclosure located in the natural geographic range of Hermann's tortoises.

Basically the result was that the mean ± SD plasma 25-hydroxyvitamin D3 concentrations for tortoises exposed to the mercury-vapor and fluorescent lamps were significantly lower on day 35 than they were on day 0, while the mean ± SD plasma 25-hydroxyvitamin D3 concentration for tortoises exposed to sunlight did not differ significantly between days 0. Mean day 35 plasma 25-hydroxyvitamin D3 concentration was significantly higher for tortoises exposed to sunlight versus those exposed to mercury-vapor or fluorescent lamps. Sunlight provided significantly more UVB radiation than did the mercury-vapor or fluorescent lamps.

These results aren't of course conclusive, but it just goes to show how much of the info we can't be 100% sure of yet. So, it is clear why there is so much conflicting advice

Also, here is a study claiming that artificial UV light is effective enough on bearded dragons, but not tortoises: https://d1wqtxts1xzle7.cloudfront.n...-1gENAgCmQ__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA

 

[Alex and the Redfoot]

I wasn't able to find the resources referenced in those articles, but I found one study that might be the kind they are referencing with a quick search on google scholar: https://avmajournals.avma.org/view/journals/ajvr/73/11/ajvr.73.11.1781.xml

This experiment was done using a self-ballasted mercury-vapor lamp and a fluorescent UVB-emitting lamp. These were compared to a group of tortoises that were exposed to sunlight in an outdoor enclosure located in the natural geographic range of Hermann's tortoises.

Basically the result was that the mean ± SD plasma 25-hydroxyvitamin D3 concentrations for tortoises exposed to the mercury-vapor and fluorescent lamps were significantly lower on day 35 than they were on day 0, while the mean ± SD plasma 25-hydroxyvitamin D3 concentration for tortoises exposed to sunlight did not differ significantly between days 0. Mean day 35 plasma 25-hydroxyvitamin D3 concentration was significantly higher for tortoises exposed to sunlight versus those exposed to mercury-vapor or fluorescent lamps. Sunlight provided significantly more UVB radiation than did the mercury-vapor or fluorescent lamps.

These results aren't of course conclusive, but it just goes to show how much of the info we can't be 100% sure of yet. So, it is clear why there is so much conflicting advice

And here go the lamps they were using:

Solar Glo, 125-W mercury-vapor bulb, Exo Terra, Rolf C. Hagen Inc, Montréal, QC, Canada.

Repti Glo 5.0, 24-W fluorescent bulb, Exo Terra, Rolf C. Hagen Inc, Montréal, QC, Canada.

I suspect, 12 years ago they were less effective than now and perhaps had worse spectre. And T8 5.0 (5% UVB?) is not a good choice for testudos. Maybe UVGuide has old reports on these.

 

[The_Four_Toed_Edward]

And here go the lamps they were using:

Solar Glo, 125-W mercury-vapor bulb, Exo Terra, Rolf C. Hagen Inc, Montréal, QC, Canada.

Repti Glo 5.0, 24-W fluorescent bulb, Exo Terra, Rolf C. Hagen Inc, Montréal, QC, Canada.

I suspect, 12 years ago they were less effective than now and perhaps had worse spectre. And T8 5.0 (5% UVB?) is not a good choice for testudos. Maybe UVGuide has old reports on these.

Yeah, that just goes to show how technology has advanced. I chose the source, since it was from the same time period as the articles I read. You are probably right that the bulbs used in these kind of studies are a better fit to some other reptiles.

 

[Alex and the Redfoot]

Also, here is a study claiming that artificial UV light is effective enough on bearded dragons, but not tortoises: https://d1wqtxts1xzle7.cloudfront.net/67426553/Effects_of_different_vitamin_D_sources_on_blood_biochemistry_of_bearded_dragons_and_Hermann_s_tortoises-libre.pdf?1621949809=&response-content-disposition=inline;+filename=Effects_of_two_dietary_vitamin_and_miner.pdf&Expires=1713346062&Signature=KGpGrBu6xlgd5hlLr19Gc2azbw~1TTUZ1NwP34iuX4mZlkZvWO56y4WvwrefJx5C2aoZE47IKP2rwueVVWCi1carYyx16jJinDyCpeGNjkiuBfG3WqAx9~7WMd04tud77Ps1kdbOL~2kNYXL-yKs5miEYjGbs77X2P62rtwLWnttRZo2L6jXVjsESEpb3T3TtXBqwS1Hov1kU6Xbv2J~RDDwEjPFOUE9r4Tey4NX4PBvoWON5LzpQzvfqXmv8INAgpJgE5VY3VJXuIf7cewUaH4p378X5-Kg6A5dr9WMGrMR8INjZdfUP5J8zr5GceDKosGKHTDAhUDO-1gENAgCmQ__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA

This one is recent enough. Thank you! I'll take a look later.

Perhaps, Markw84 and jaizei can explain everything (they are probably most knowledgeable on this topic out of active forum members). I don't mention them in hope they will find this thread when they have enough time.