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Reptilian Nutrition and Disease

  1. #1
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    Reptilian Nutrition and Disease

    Without a doubt, one of the main concerns in herpetological care are health problems arising from an inadequate diet. Nutritional requirements will vary between species as well as individuals depending on their health, reproductive status and age. Feeding your reptile the appropriate foods and quantities is essential for long-term health and longevity. The key to preventing nutritionally related diseases is to be familiar with the specific requirements of the species in your care. Appropriate heating also plays an important role in nutrition. In ectothermic animals the metabolic processes governing digestion are dependent on environmental factors, mainly temperature. If these environmental factors are not optimal, even a perfectly balanced meal could go to waste because of inadequate digestion.



    Reptiles can roughly be divided into three nutritional groups: herbivores, omnivores and carnivores. Each of the groups has their own set of typical problems. Knowing which nutritional category your species belongs to will help you with diagnosis of nutritionally related disorders. However, any disease may be found in nearly any species.

    Generally, the diseases related to nutrition can be roughly divided into two groups: either caused by a deficiency or a toxic overdose of a certain nutrient.

    Although nutritional supplementing is likely essential for herbivorous and insectivorous reptiles, very little research has been conducted to establish specific nutritional needs of reptiles. Optimal supplementing is likely to vary depending on the nutritional content of the animal feed, body size, age, health status and other factors. Typical recommendations on using powdered supplements is to dust the animals feed every other feeding session. Species specific supplements are available to provide the reptile with the most necessary nutrients for optimum health.

    There are two main nutrients to consider; vitamins and minerals. Other nutrients include proteins, carbohydrates, fats and fibre. Herbivorous reptiles are likely to be exposed to anti-nutritional factors from the vegetables they eat which decreases the bioavailability of specific nutrients. You will need to be aware of these compounds so not to overburden the reptile with anti-nutrients by inappropriate feeding of vegetables high in these compounds. Nutrition within an animal will affect all aspects of the animals development, if the animal does not receive the required level of nutrition or is given more than the body requires the animal will become prone to disease and illness as deficiencies or toxicities occur. This will be discussed below…

  2. #2
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    VITAMINS


    Vitamin A



    Function

    Vitamin A is important for the maintenance of vision (especially in dim light), growth and development, repairing of damaged tissues, new cell growth and cell differentiation, the immune function and is important for the proper functioning of the eyes, skin, mucus membranes and ducts.


    Vulnerable Species

    Herbivores: Hypovitaminosis A is a commonly seen problem in chelonians such as box turtles, young red eared terrapins and other chelonians.



    Deficiency


    As vitamin A plays such a key role in the maintenance of the mucus membranes a deficiency will show immediate changes. The mucus membranes will harden and thicken causing the salivary and mucus glands to block up. This causes the oral and respiratory secretions to dry and cellular debris to build up because of poor functioning of the ciliary mechanisms whose role is in the removal of foreign particles from the airways. Swelling of the eyelids is also commonly observed along with the development of a condition known as xerophthalmia (dry eyes), as displayed in the picture above. A "parrot beak" and/or oral abscesses may also be indications of a diet lacking in vitamin A or beta-carotene. Other symptoms may include a runny nose, wheezing, raw infected skin, thickening of the horny layers of the skin, oedema (the swelling of the limbs due to fluid accumulation because of liver failure), and loss of appetite and weight.

    It's role in the maintenance of the immune system means a deficiency makes respiratory and digestive tract infections more common. The most frequently seen example is pneumonia as seen in red eared terrapins which adopt a lop-sided position when swimming due to lung collapse or congestion which reduces buoyancy on the affected side. Upper respiratory tract infections are also common in tortoises suffering from hypovitaminosis A.


    Toxicity

    Toxicities are rare and are typically caused by over-supplementation or rarely through veterinarian error when excessively high concentrations of vitamin A are administered via injection. Acute toxicity develops with clinical signs appearing as dermal burns caused by dry skin that sloughs off leaving red raw patches, abnormal bone development and liver enlargement. Frequently death occurs within 24- 48 hours.


    Prevention

    Appropriate oral supplementation of vitamin A or Beta-carotene is recommended along with the inclusion of foods containing vitiamin A or beta-carotene within the animals diet. (N.B.- Beta-carotene is the main safe dietary source of vitamin A).

    Injections with highly concentrated vitamin A are an option but are not recommended. Supplements given orally are absorbed much slower into the system than if they were injected allowing for a safer and more controlled rate of absorption. Animals suffering with dermal burns due to hypervitaminosis A should be given burn wound therapy, antibiotics and open wounds addressed.


    Foods

    Vitamin A is found in dark green and yellow vegetables and yellow fruits, such as watercress, swiss chard, turnip greens, carrots, squash (butternut squash), sweet potatoes, pumpkin, cantaloupe, and apricots, and for non-herbivorous species vitamin A can be obtained from animal sources such as liver and whole eggs.



    Vitamin B1 (Thiamine)



    Function

    Needed for energy metabolism and the proper functioning of the nervous system.


    Vulnerable Species

    Largely seen in fish eating animals such as Garter Snakes, Gharials and aquatic Turtles as well as herbivores like the Green Iguana.



    Deficiency


    Hypovitaminosis B1 is a disease commonly caused by the feeding of large quantities of raw fish, particularly salt water fish. This is due to the fact that the guts of fish house an enzyme known as Thiaminase which deactivates vitamin B1 rendering it useless. The freezing of green vegetables, especially leafy greens, can also cause it as the freezing process causes a leaching out of B1. Clinical signs may include weight loss despite eating well, but are largely neurological and includes a lack of balance or coordination, opistholonus (hyperextension of the body), blindness, torticollis (abnormal head position), weakness, sinking of the eyes into the orbit and twitches and head tremors. Garter and water snakes display an inability to right themselves with the snake continually flipping onto its back. It also affects the nervous system in snakes that are fed exclusively on fish, giving rise to convulsions and ultimately death. Fish that contain particularly high concentrations of this enzyme include; smelt, milkfish, green snapper, cod, grey mullet and can also be found in others like minnows and goldfish.

    Reptiles also synthesis vitamin B1 within the intestinal tract, antibiotic therapy may induce thiamine deficiency by killing the intestinal microflora.


    Prevention

    A deficiency can be avoided by feeding fish that have been gutted, as most thiaminase is present in the gut, or by lightly pre-cooking the fish, which will inactivate the thiaminase enzyme. It has been reported that if fish are heated to 80˚C for five minutes prior to feeding, the enzyme is destroyed. It has been further recommended, to add 20mg B1 to each kg of fish after cooling before being fed to the animal; however, the deficiency can also occur even when fish are fed together with a vitamin B supplement because relatively small amounts of the enzyme thiaminase are able to deactivate very large amounts of thiamine.

    Because of this problem it is often advised feeding garter and water snakes on rodent prey rather than fish.


    If the reptiles intestinal microflora has been compromised by antibiotic treatment, this microflora can be reintroduced by feeding Lactobacillus cultured products.



    Vitamin B7 (Biotin)



    Function

    Necessary for cell growth, the production of fatty acids, and the metabolism of fats and amino acids.


    Vulnerable species

    Gila Monsters, Bearded Lizards and Monitor Lizards


    Deficiecy

    A biotin deficiency can only be induced if the reptiles' diet consists of 100 percent raw eggs. Even though this seems very unlikely, cases have been reported in species like Monitors (Varanus sp.) and Gila Monsters which enjoy raw eggs in the wild and have been fed a diet consisting of exclusively raw eggs in captivity. Although the egg yolk contains high levels of B vitamins, the raw egg white contains the anti-nutritive factor avidin, which binds to biotin, making it unavailable to the body. In the wild, most eggs consumed by reptiles are already fertile or have been incubated for a period of time, which in turn decreases the avidin content. However, unfertilised hens eggs are high in avidin, these are the eggs which are fed in captivity. Furthermore, these oviphagous reptiles would likely eat other items in addition to eggs. Clinical signs usually manifest themselves as skin lesions, muscular weakness, tremors and anorexia.


    Prevention

    A change in the diet with the inclusion of raw meat and small mammals and vitamin supplementation is usually enough to reverse the damage. It is recommended to feed a minimal level of raw eggs to such reptiles.



    Vitamin C



    Function

    It is an antioxidant vitamin needed for the formation of collagen to hold the cells together and for healthy teeth, gums and blood vessels; also improves iron absorption and resistance to infection.


    Deficiency


    Vitamin C is typically synthesized in sufficient quantities in the kidneys and/or intestines by microflora within the gastrointestinal tract of reptiles, so if internal synthesis were impaired by renal or intestinal disease than dietary sources may be insufficient to meet requirements for this vitamin. vitamin C deficiency causes the onset of scurvy which may be identified by sudden skin rupturing or spontaneous bleeding from the gums. Scurvy can cause reduced collagen synthesis or decreased strength of certain tissues, including skin and blood vessels. Vitamin C deficiency is suspected to be important in the occurrence of mouth rot (stomatitis) in reptiles and also other problems such as poor wound healing.

    Vitamin C deficiency may also occur in reptiles fed on rodents that possess a deficiency due to underfeeding prior to being offered as food.


    Prevention

    prey animals should be fed adaquatly before being fed to the reptile or culled and stored. Oral supplementation of ascorbic acid may also be recommended.



    Vitamin D3 (See also Calcium and post on MBD)



    Function

    Promotes absorption and use of calcium and phosphorus from the intestinal tract for healthy bones and teeth.


    Deficiency

    Vitamin D3 aids in calcium homeostasis by facilitating the absorption of calcium. This nutrient can be obtained either from the diet or produced in the skin after exposure to Ultra-Violet Light. 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.


    Toxicity

    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. This often occurs in herbivores such as tortoises fed on tinned cat and dog food. Excess supplementation must be avoided as this too can lead to problems of calcification of the soft tissues.


    Prevention

    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.



    Vitamin E



    Function

    Protects red blood cells and helps prevent destruction of vitamin A and C.


    Deficiency

    This disease can cause steatitis (yellow fat disease) and mostly affects aquatic reptilian species (such as crocodilians and chelonians) that have been fed a diet consisting mainly of fish with a high percentage of polyunsaturated fatty acids, e.g. fish like tuna, mackerel, mullet and smelt. Reptiles that have been fed mainly obese rats can also develop the condition because of the increased fat content of the prey animal. Polyunsaturated fatty acids use up the bodies vitamin E reserves. If the food animals were not stored appropriately, the fatty acids in the carcass can become rancid, contributing significantly to the disease. Clinical signs can be subtle, from anorexia to more specific signs, such as lingual ulcerations due to the hardening of the fat pad at the base of the tongue. Organs may adhere to one another causing the development of large tissue masses, along with necrosis of the liver and lesions on the skin. The skin may also become necrotic and slough due to the development of a condition called ischemia. Vitamin E deficiency may also result in cardiac or skeletal muscle weakness leading to myopathy and cardiomyopathy, death may result.


    Toxicity

    Hypervitaminosis E is very rare but may occur because of a reduction in fat metabolism or absorption due to lack of dietary green plant material for herbivores.


    Prevention

    Supplementation with vitamin E and correct feeding techniques help prevent this disease. Excess oily fish or fish oil supplements should be avoided, and vitamin E supplementation has been recommended to reduce the likelihood of steatitis developing in reptiles fed on a high fish ration. Fish and other feeder animals should be fed as fresh as possible and a varied diet is further recommended.



    Vitamin K


    Function

    Necessary for normal blood clotting and synthesis of proteins found in plasma, bone, and kidneys.


    Deficiency

    Vitamin K deficiency is relatively rare but has mainly been reported to occur in crocodilians. Vitamin K is normally produced by bacteria in the intestinal tract. If prolonged antibiotics are given this can upset the normal bacteria resulting in inadequate vitamin K production. A deficiency usually appears as a spontaneous haemorrhage, like bleeding from the gums.


    Prevention


    Supplementation of vitamin K may be provided. A varied diet may also reduce the incidence of this disorder.
    Last edited by Cat001; 11-23-2017 at 09:06 PM.

  3. #3
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    MINERALS


    Calcium (Ca) (See also Vitamin D3 and MBD)



    Function

    Needed for healthy bones and teeth, normal blood clotting, muscle and nervous system functioning.


    Deficiency

    Calcium is an essential ion in the body which is responsible for a large number of important physiological processes such as muscular contractions, the formation of the skeleton and mineralisation of bone matrix. Bones represent a large reservoir for calcium storage holding 99% of calcium in the body which is deposited as a crystalline form.

    When the available level of free calcium in the blood drops, calcium is then released from the bones into the blood system. Extensive resorption of calcium occurs from bones during dietary deficiencies, leaving only fibrous tissue , this is considerably weaker and so the ‘bones’ thicken to maintain their strength. Even so the bones are weakened, and bowing of long bones and spontaneous fractures occur in lizards, collapsing of spinal vertebrates and deformities in most reptiles and deformed, lumpy shells in chelonians. A calcium deficiency can result in a number of problems apart from malformation of the skeleton including the thinning of the eggshells and problems with the nerves and muscles. a drop in calcium causes the over-excitability of nerves and muscles as calcium has an influence on the membrane permeability to Sodium. When calcium levels fall, sodium permeability increases which causes skeletal muscles to discharge and contract resulting in muscle spasms. In severe cases this can interfere with respiratory muscles that may result in death by asphyxiation. A drop in calcium levels to such an extent may be the result of vitamin D deficiency (caused typically by insufficient levels in the diet or less commonly from renal or liver disease), excessive levels of phosphorus, or hypoparathyroidism, either due to damage to the parathyroid glands or their removal after surgery.

    The ratio of calcium to phosphorus is important - as one increases the other decreases and vice versa. A ratio of 2:1 calcium to phosphorus is desirable in growing reptiles and 1.5:1 for adults. In high egg laying periods, to keep pace with output of calcium into shells 10:1 may be needed.

    Deficiencies may be seen in lizards such as green iguanas water dragons and chelonians fed on diets with excessive levels of oxalates, (compounds which bind calcium and prevent absorption). These foods include: spinach, rhubarb, cabbage, peas, potatoes and beet greens which are occasionally fed to herbivorous and omnivorous species of reptiles in excessive amounts. Additionally, other foods contain very little calcium such as celery, cucumber and lettuce and therefore should be fed sparingly to herbivorous reptiles. In the case of carnivorous reptiles, feeder insects are generally very low in calcium content whilst inversely high in phosphorus. For this reason supplementation and ‘gut loading’ of the live prey is required. Feeding of meat without bone has also contributed to nutritional imbalances. Excessive phosphorus levels can be an issue as they cause the formation of insoluble calcium phosphate which reduces levels of usable calcium.


    Toxicity

    There is considerable focus on insufficient calcium causing problems but it is important to be aware that excess can also create its own issues. Excesses in calcium can lead to the formation of renal stones which may induce nausea and sickness along with abdominal pain and the onset of renal hypertension, also acute pancreatitis, muscle weakness, fatigue and cardiac disorders. Causes include hyperthyroidism and hyperparathyroidism leading to the over activation of vitamin D3 and excessive absorption of calcium via the GI tract as well as excessive bone resorption. Excessive calcium also reduces the use of proteins, fats, phosphorus, magnesium, zinc, iron, iodine and can lead to soft tissue mineralisation if in conjunction with inadequate or excessive Vitamin D3 levels.


    Prevention

    The correct ratio of calcium to phosphorus must be provided along with the correct provision of vitamin D3, either from the use of UV lighting or supplementation as appropriate to the species.



    Iodine (I)



    Vulnerable Species

    Tortoises, especially Giant Land Tortoises.


    Deficiency

    Iodine deficiency is reported to be common in tortoises, which results in inadequate amounts of thyroid hormone being produced (a condition called hypothyroidism). This condition is seen most often in Giant Land Tortoises which have a high requirement for iodine, and also in reptiles fed high quantities of brassica plants (a group of plants which includes cabbage, cauliflower, kale. rape, swede, turnip, brussels sprouts, and broccoli) which are high in goitrogens. (goitergens - supress thyroid function). Iodine deficiency causes goitre, the swelling of the neck and fluid retention (myxoedema).


    Toxicity

    Like with a deficiency,iodine toxicity can result in the development of goitre. Excess iodine added to water may cause species such as the axlotle to shed its external gills.



    Phosphorus (P) (See also MBD)


    Function

    Needed for healthy bones and teeth, energy metabolism, and acidbase balance in the body.


    Deficiency

    Phosphorus is widespread in plant and animal tissue, but in some plants may be bound up in an unavailable form known as phytates.


    Toxicity

    Levels of phosphorus are controlled in the body as they are for calcium, the two being in equal and opposite equilibrium with each other. Therefore if dietary phosphorus levels exceed calcium levels appreciably the parathyroid glands become stimulated to produce more parathyroid hormone and nutritional secondary hyperparathyroidism occurs. Phosphorus influences the bioavialability of calcium as it binds with Calcium to form an insoluble salt which is deposited in the bones thereby reducing the useable levels of Calcium. This leads to progressive bone demineralisation and renal damage due to high circulating levels of parathyroid hormone. High phosphorus reduces the amount of calcium which can be absorbed from the gut, as it complexes with calcium present there. This is a problem in reptiles fed pure meat with no calcium or bone supplement, and in herbivores which are predominantly fruit and lettuce consumers as these are high phosphorus low calcium foods. Furthermore, low calcium / high phosphorus diets frequently allow bladder stones to form.


    Prevention

    Animals must be given the correct phosphorus to calcium ratio through appropriate feeding and correct supplementation.



    Selenium (Se)


    Function

    A trace element that plays a role in immune function and reproduction. It further prevents damage to cells and tissues.


    Deficiency

    Selenium is seldom mentioned in reptile nutrition yet it is a critical nutrient. symptoms of a deficiency usually appear similar to that of a vitamin E deficiency and can impact on muscles, immune function, vision, and/or the nervous system.


    Toxicity

    A toxicity may cause abnormalities to the nails and skin and softening of the bones (selenosis).
    Last edited by Cat001; 11-23-2017 at 09:13 PM.

  4. #4
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    ANTI-NUTRIENTS


    Oxalates

    Oxalates chiefly affects calcium but also has an affect with magnesium metabolism. Calcium Oxalic acid binds calcium and forms calcium oxalate which is insoluble, indigestible crystals. Therefore, calcium oxalate adversely affects the absorption and utilisation of calcium in the animals' body.

    Spinach, for example, contains a high level of calcium, but the oxalic acid it also contains binds up all but about 5% of it during the digestion process, working at a rate of 1 unit of oxalic acid binding up almost 100 units of calcium. Vitamin A can help reduce the effect a little. A positive feature of oxalic acid is that the crystals help clean the digestive system and may offer some other benefits in small amounts. Foods high in oxalic acid include spinach, kale, lettuce, broccoli, swiss chard and parsley. A varied diet can prevent any nutritional issue, as well as careful and moderate feeding of foods high in oxalic acid.



    Goitrogens

    Goitrogens cause an enlargement of the thyroid gland, and contribute to the develop of goitre (swelling of the neck) by blocking iodine absorption.Since thyroid hormones play an important part in the control of body metabolism their deficiency results in reduced growth and reproductive performance. They are found in many foods, such as legumes (e.g. soybean and groundnut), strawberries, peaches, radishes, brassicas (cabbages, broccoli, and all of the greens- turnip, radish, mustard, collards, etc). A varied diet can prevent any nutritional issue, as well as careful and moderate feeding of foods high in goitrogens.



    Tannins

    Tannins are water soluble compounds that bind with proteins and Iron. Tannins also have the ability to complex with vitamin B12 and have been reported to cause intestinal damage and may possibly cause cancer. Tannins are found in many sour tasting fruits and berries includingsour grapes, pomegranates, and persimmons. These compounds are one of the reasons that oak leaves and acorns are considered toxic to reptiles.



    Phytic Acid


    Phytic acid occurs naturally throughout the plant kingdom and is present in considerable quantities within many of the major legumes and oilseeds. This includes peas, beans, nuts, grains and seeds. Phytic acid acts as a strong chelator, forming protein and mineral-phytic acid complexes; the net result being reduced protein and mineral bioavailability. Phytic acid is reported to chelate metal ions such as calcium, magnesium, zinc, copper and iron to form insoluble complexes that are not readily absorbed from gastrointestinal tract. (Chelate comes from the word for ‘lobster claw’, and came to mean ‘shell’ in general. Here it is used to refer to the way chelating agents ‘grab’ nutrients). It has been found that the greatest effect of phytic acid on human nutrition is its reduction of zinc bioavailability. The major part of the phosphorus contained within phytic acid are largely unavailable to animals due to the absence of the enzyme phytase within the digestive tract of many animals, however, in other animals it can help make phosphorous bio-available to the animal eating it. It is advised to avoid raw, unprocessed seeds and grains.

Please reply to this thread with any new information or opinions.

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