All about vitamins, minerals and Tortoises
A C Highfield
There is a great deal of misunderstanding concerning the role of
vitamins and minerals. Many people believe that the more you get of
both the better - this is categorically not true, indeed, some
vitamins and minerals can be positively dangerous if taken in excess.
What is actually required is a balanced intake of essential vitamins
and trace-elements - not massive doses of individual vitamins in
isolation which serve only to upset the balance and may cause relative
deficiencies elsewhere.
It is also important to dispense with the myths, common among
tortoise keepers, that vitamin deficiencies are the cause of a great
deal of frequently encountered diseases or that a vitamin injection
is necessary to assist with hibernation. Both claims are totally
incorrect. 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.
There are two common ways in which additional vitamins may be given:
Oral vitamin supplements
These are useful as a guarantee that all necessary vitamins are being
supplied - but again, they are not essential if the base-line diet is
of high quality and is sufficiently varied. Animals on natural browse
do not need vitamin supplements, although calcium supplements may still be necessary.
Vitamin injections
These should only be used to deliver specific vitamins in cases where
a specific vitamin deficiency is known to exist. We are totally
opposed to the routine use of vitamin injections - in most cases, they
serve no useful purpose and indeed are a frequent cause of introduced
infection via the injection site. Very few deficiencies are so acute
that the much more effective and safer oral delivery route is not a
satisfactory mode of treatment. Acute vitamin-A deficiencies may be
dealt with by injection, but few other cases require this treatment.
The use of a routine "vitamin booster" before or after hibernation is
a complete waste of time.
VITAMINS Vs. MINERALS
Many people are unclear as to the difference between vitamins and
minerals, and especially about how the two interact (many minerals,
calcium for example, depend upon the presence of certain vitamins
such as vitamin-D before they can be absorbed).
Vitamins are organic substances which help regulate bodily functions.
Acting as co-enzymes, vitamins aid the action of enzymes during the
metabolism of dietary nutrients. There are about a dozen major
vitamins, a deficiency of any one of which will result in a serious
deficiency disease. Vitamins are only required in relatively small
quantities, but have a major effect upon the body's reproductive,
digestive, nervous and muscular systems. Vitamins also affect tissue
growth and anti-body production.
Some important vitamins are:
VITAMIN-A
Important to the condition of the skin and mucous membranes, eye
(especially retinal) condition, biochemical and reproductive
functions. Plants contain carotene which is converted to true
vitamin-A in the body.
VITAMIN-B COMPLEX
The B-complex vitamins are water soluble and excesses are excreted in
the urine. Vitamin B1, thiamine, is a regulator in the carbohydrate
metabolism; Vitamin B2, riboflavin, is a co-enzyme in energy release
and interacts with vitamin B6 and vitamin B12; Vitamin B3, niacin, is
also crucial to the energy metabolism and is often obtained by
converting the amino-acid tryptophan - this process requires the
presence of thiamine, riboflavin and pyridoxine; Vitamin B6,
pyridoxine, is involved in energy conversion from glycogen and in the
synthesis of haemoglobin and antibodies; Vitamin B12 interacts with
folic acid to govern the production of red blood cells. A deficiency
causes pernicious anaemia and neurological symptoms. This vitamin is
only produced within the gastro-intestinal tract when various
micro-organisms act upon trace level cobalt. Deficiencies can occur
following malabsorbtion syndrome or as a consequence of severe
parasite infestations. The B-complex is just that. A matrix of
interacting and inter-dependant compounds.
VITAMIN-D
Sometimes called 'the sunshine vitamin', vitamin-D is a fat soluble
vitamin which is essential to the absorption and utilisation of
calcium and phosphorous, as such, it plays a major role in bone
formation. It can be obtained either naturally, by the action of
ultra-violet light on sterols in the skin, or orally by
supplementation - virtually all specialist calcium/mineral supplements intended
for reptile use contain
vitamin D in sufficient quantity.
VITAMIN-C
Vitamin-C has many functions, but as it is present in almost all
fruits and green vegetables, deficiencies are extremely unlikely in
tortoises.
VITAMIN-E
Many plants contain vitamin-E which is an antioxidant and works in
conjunction with vitamins A and C.
VITAMIN-K
A fat-soluble coagulation vitamin. This vitamin is synthesised in the
gut by bacterial action and is also found in plant foods. It is
especially abundant in green, leafy plants.
MINERALS
Minerals are quite different from vitamins and are both chemical
regulators and construction materials - Calcium forms a major part of
a tortoise's body, more than any other mineral. Calcium deficiency is
also extremely common as a growing tortoise requires substantial
quantities of this mineral in order to build its skeleton.
The building of healthy bone tissue is the result of many vitamins and
minerals acting in cooperation with each other.
It is essential to note that calcium is poorly absorbed by the body
whereas phosphorus is readily absorbed - if a diet is heavy in
phosphorus in relation to calcium, the excess phosphorus will prevent the uptake
of calcium to the bone. It is very easy to
feed a diet too concentrated in phosphorus because it is available in
nearly every foodstuff whereas calcium is relatively rare. We must
knowingly choose calcium bearing foods when designing diets for
captive animals.
Calcium and phosphorus together account for three-fourths of the
mineral elements in the body, and five other elements account for most
of the rest. It is important to note that their actions are
interrelated; no one mineral can function without affecting the
others.
The major function of calcium is to act in cooperation with phosphorus
to build and maintain bones. Calcium is essential for healthy blood
and also helps to regulate heartbeat. In addition, calcium assists in
the process of blood clotting and helps prevent the accumulation of
too much acid or too much alkali in the blood. It also plays a part
in muscle growth, muscle contraction and nerve transmission. 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.
Calcium absorption is very inefficient. Two factors effect absorption
directly; the availability of calcium in the diet and the current body
need. Unabsorbed calcium is excreted.
Certain substances interfere with the absorption of calcium. When
excessive amounts of fat combine with calcium, an insoluble compound
is formed which cannot be absorbed. Other substances that can disrupt this process
include oxalates and phytic acid.
Phosphorus
Phosphorus is the second most abundant mineral in the body. It functions along with calcium. A
balance of calcium and phosphorus is needed for these minerals to be
effectively used by the body.
Phosphorus plays an important part in almost every chemical reaction
within the body. It is important in the utilization of carbohydrates,
fats and protein for growth, maintenance, and repair of cells and for
the production of energy. It aids in the transference of heredity
traits from parents to offspring. It is also necessary for proper
skeletal growth, kidney function and transference of nerve impulses.
If phosphorus content is high, additional calcium must be taken to
maintain proper balance. Phosphorus is available in a wide variety of foods
and further supplementation is not necessary.
Miscellaneous trace elements
Calcium, chlorine, phosphorus, potassium, magnesium, sodium, and
sulfur are present in relatively high amounts in the body tissues.
Other minerals are present in the most minute quantities but are
essential for proper body functioning. Iron, copper, and fluorine are
present in sufficient quantities from deep green leafy plants. Iodine
is needed to maintain a positive calcium balance, so a multi-mineral
mixture containing iodine should be provided in addition to
supplementation of raw calcium.
GENERAL GUIDELINES
Try to ensure that all diets are as varied as possible - in this way,
a wide cross-section of trace elements will be made available.
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.
Provide vitamins orally rather than by injection for preference.
The regular use of a safe, properly formulated multi-vitamin and
mineral preparation will ensure that dietary deficiencies do not
occur.
Aim for a high calcium - low phosphorous
balance in tortoise diets
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