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Zoological Medicine 2008
Wildlife and Exotic Animal Nutrition
G. Kaufman, DVM
Tufts University
2008

1. Basics

Feeding wildlife and exotic animals can be one of the most challenging aspects of their care. In fact, errors in nutritional management are often the primary cause of disease and death in these animals. Mistakes are made for a variety of reasons. Often times the caretaker is simply ignorant of generally well documented facts concerning the feeding of the particular animal. This may be due to misinformation in popular literature, someone else's misguided experience, or poor intuition and research on the part of the owner. However, nearly as often the facts are simply not known and even well researched and thought out nutritional strategies omit an essential component or balance of nutrients required for the animals health and/or survival. For some reason animals seem to make it into captivity faster than they can be thoroughly studied in the wild. This disparity then produces unfortunate circumstances of high captive mortality, poor reproductive success in captivity, and further exploitation or depletion of wild populations to fulfill whatever demand is driving the system.

The grass is always greener...reaching for fresh grass.
The grass is always greener...reaching for fresh grass.

How do we face this challenge with animals we know so little about? Thoroughly researching the available literature is an obvious place to start, but often without easy answers. Many reports are contradictory and require some discrimination or first hand knowledge to feel confident about the information. Two types of basic information are essential to "guessing" an appropriate regimen.

  • What do we know about the animals "wild" diet?

  • Is there a domestic animal model that is similar physiologically and/or phylogenetically?

This information is useful to help recreate the correct diet, and also to allow utilization of commercially available diets and supplements that could assist in providing a reasonably balanced diet. It would be nearly impossible to simulate the "wild diet" exactly even if this information was known (unlikely). The types of animal foodstuffs and plant foodstuffs found in the wild setting are simply not available in the supermarket or through a supply catalog. Our best guesses can hopefully be formulated utilizing knowledge of the nutritional contents of available fresh foods and prepared animal diets to provide a consistent source of balanced and readily available food. Closely monitoring and recording growth, reproduction, longevity and general health is always required to verify an adequate nutritional strategy. Flexibility must be maintained to adjust the diet as information becomes available.

1.1. Commercial resources

In addition to the conventional domestic animal diets, there are several companies that offer non-domestic diets or supplements. These have been very useful and should be utilized when possible to help take the guess work out of balancing a ration. Some resources are sited below, others are mentioned in the Appendix of the textbook (Hand, c2000):

  • Mazuri foods, a division of Purina Mills, Inc. PO Box 66812, St. Louis MO 63166-6812, providing the widest selection of zoo animal feeds for reptiles, birds and mammals. http://www.mazuri.com/

  • Zeigler Bros., Inc. PO Box 95, Gardners, PA, 17324-0095. Zoo animal and pet exotic diets. http://www.zeiglerfeed.com/

  • Premium Nutrition Products, Inc. PO Box 2094, Mission, KS 66202, Zupreem diets. http://www.zupreem.com/

  • Multi-Milk and Zoologic milk replacers from Pet-Ag, Inc. 30W432 Rte. 20, Elgin, IL 60120 http://www.petag.com/

  • Oxbow Animal Health. 29012 Mill Rd., Murdock NE 68407, 1-800-249-0366. Pet rabbit and rodent diets. http://www.oxbowanimalhealth.com/

  • Nutrition Support Services, Inc. Walkabout Farm, PO Box 625 Pembroke, VA 24136. Owner: Susan Donoghue, VMD, DACVN Phone: (540) 626-3081 Fax: (540) 626-3564 E-Mail: WalkaboutF@aol.com http://www.herpnutrition.com/

  • Harrison's Bird Foods http://www.harrisonsbirdfoods.com/ 7108 Crossroads Blvd., Suite 325, Brentwood, TN 37027, 1-800-346-0269

  • Kaytee birds and small animal food http://www.kaytee.com/

  • Pretty Bird International, 5810 Stacy Trail , Stacy, MN 55079, 1-800-356-5020, http://www.prettybird.com/

    Food warning
    Food warning

    Feed guide
    Feed guide

2. Mammals – Rabbit and Rodent nutrition

Rabbits and rodents have been used in research for a long time. With the recent upsurge in pet ownership, there have been important advances made in understanding rabbit nutrition particularly and have resulted in many improvements in available formulated diets for these animals.

2.1. Rabbits

Rabbits are true herbivores and are considered monogastric hind gut fermenters (similar to a horse). Wild rabbits are considered 'browsers', and are very selective in what they eat.

Rabbit GI Tract

large distensible stomach (155 of total volume

large distensible stomach (15% of total volume)

large intestine

sacculus rotundus rabbit only

cecum (40%)

colon 1 meter long in NZW

Cecotrophy or coprophagy is a necessary part of a rabbits daily routine and is required for efficient use of their herbivore diet. Additional vitamins and proteins are obtained through this behavior. The special "cecal pellets" are normally produced at night or early morning and are also called "night feces".

Rabbits have very efficient gastrointestinal absorption of calcium in the diet. They normally maintain high serum calcium levels (up to 14 mg/dl), and excrete most of the excess calcium through the kidneys (as opposed to the liver/bile in other mammals). This is true of wild rabbits, cottontails and pikas as well.

In captivity our domestic rabbits are classically fed rabbit pellets with or without supplemental foods. Most available rabbit pelleted rations are designed for laboratory use and are not always suitable for pet rabbits.

Diets including rabbit pellets alone or rabbit pellets and alfalfa hay have been linked to disorders of excessive calcium, obesity, hepatic lipidosis and chronic soft stools. One source recommends calcium at 0.4 - 0.5% of the diet for non-lactating animals. Processed rabbit diets are usually very high in calcium (e.g. see above) and may produce hypercalcemia and related disorders, most often involving the urinary tract. Vitamin D in the diet does not seem to influence the uptake of dietary calcium, but may influence the development of soft tissue mineralization.

Purina Rabbit Chow Complete Blend

Oxbow Bunny Basics/T

Guaranteed Analysis

Guaranteed Analysis

Crude Protein, not less than

16.0%

Crude Protein (min)

14.00%

Crude Fat, not less than

1.5%

Crude Fat (min)

1.50%

Crude Fiber, not less than

17.0%

Crude Fiber (min)

25.00

Crude Fiber, not more than

20.0%

Crude Fiber (max)

28.00%

Calcium, not less than

0.6%

Moisture (max)

10.00%

Calcium, not more than

1.1%

Calcium (min)

0.35

Phosphorus, not less than

0.4%

Calcium (max)

0.80%

Salt, not less than

0.5%

Phosphorus (min)

0.25%

Salt, not more than

1.0%

Salt (min)

0.50

Vitamin A, not less than

4000 IU/lb

Salt (max)

1.00%

Vitamin A (iu/kg)

20,000

Vitamin D (iu/kg)

880

Vitamin E (iu/kg)

140

Copper (mg/kg)

20

A diet of pellets alone, without any added roughage may contribute to the development of hairballs. Roughage or fiber in the diet has been shown to increase motility. Loss of motility can contribute to the development of constipation and cecal obstruction.

The Ideal Rabbit Diet
Quality high fiber rabbit pellets (e.g. Oxbow)
Timothy hay (free choice)Fresh fruits and vegetables
Occasional other grains/treats

Timothy hay and fresh vegetables make up part of a healthy rabbit diet.
Timothy hay and fresh vegetables make up part of a healthy rabbit diet.

It is recommended to supplement pelleted diets with additional fiber such as timothy hay (lower in calcium than alfalfa) and mixed vegetables and fruits. Fresh foods should be introduced gradually to allow for adequate acclimatization of the gut to the more complex components. Rapid introduction or over-consumption of fresh foods may lead to diarrhea.

2.2. Guinea Pigs

Guinea pigs are normally fed a diet including fresh good quality Guinea pig pellets and fresh fruits and vegetables. Course roughage such as hay may predispose the pig to lymphadenitis. Like rabbits, guinea pigs also have problems handling too much calcium and frequently develop idiopathic calcium related diseases, usually involving the urinary tract. Unlike rabbits, guinea pigs have an absolute dietary vitamin C requirement. A deficiency will result in scurvy and eventual death from secondary complications. Clinical signs of scurvy include a poor hair coat, anorexia, gingivitis, generalized pain, arthropathy especially at costochondral junctions, diarrhea, and respiratory infections. Vitamin C is normally added to all good quality guinea pig diets (pellets). Guinea pigs should never be fed rabbit pellets because they do not have vitamin C added. Pelleted diets must be stored adequately (dry and cool, 22°C) to preserve the vitamin content. 3 months after the date of manufacture, the vitamin C content cannot be guaranteed. Often times, the date of manufacture and the storage history prior to purchase of the pellets is unknown, allowing problems to arise. Some owners will routinely supplement their pigs with fresh citrus fruit daily, or give vitamin C supplements. Always supplement with vitamin C for any disease condition . A subclinical deficiency likely contributes to many disease states.

Vitamin C Supplementation in the Guinea Pig

200 mg/L in drinking water (fresh daily)

800 mg/kg of pelleted diet (milled)

50 mg/guinea pig/day

Laboratory guinea pig diet formulation

Crude protein

18.0%

Crude fat

4.0 %

Crude fiber

14.0%

Calcium

0.90%

Phosphorus

0.40%

Vitamin D

2.00 IU/g

Vitamin C

840 ppm

Zeigler Bros., Inc.

2.3. Rats

Rats and mice are classically fed rodent chows made for laboratory use. Many companion animals are also supplemented with fresh foods, seeds, nuts and table scraps. Rats particularly are omnivorous in their tastes and will eat just about anything. A major problem with rats in a non-laboratory setting is obesity from overindulgence and feeding too high calorie foods with little exercise. This condition will compromise their health especially later in life (2 years!).

Laboratory rodent diet formulation

Crude protein

22.0%

Crude fat

5.0 %

Crude fiber

4.0%

Calcium

1.20%

Phosphorus

0.95%

Vitamin D

4.00 IU/g

Zeigler Bros., Inc.

Wild rabbits and rodents may be fed commercial rabbit and rodent chows. Palatability and recognition may be an issue. Fresh foods are often more readily accepted and may require cutting fresh grass, clover, etc. to encourage eating in captivity. Feeding baby wild rabbits is somewhat different from domestic (European) rabbits. Sources of information include The House Rabbit Handbook (for domestic bunnies) and the NWRA's Principles of Wildlife Rehabilitation for more information on wild baby rabbits.

3. Mammals – Carnivore Nutrition

Ferrets are domestic animals that also have well researched nutritional information. They are obligate carnivores similar to cats and require higher protein and fat diets than dogs. Diets formulated specifically for ferrets are available and are preferred. Premium quality cat foods may be adequate for feeding ferrets, although cheaper generic cat foods are not adequate because they usually contain significant amounts of plant proteins which are not suitable for ferrets.

Recommended analysis for ferret diet

Crude protein

38%

Crude fat

18 %

Crude fiber

3.5%

Ash

6.5%

Moisture

6.5%

Bell, 1995

3.1. Wild Carnivores

Wild carnivores should be fed group specific commercial diets when available (e.g. Mazuri brand from Purina). Dental disease and other oral development problems may arise with carnivores when only soft foods are given. Consequently many zoos will supplement carnivore diets with bones and other sources of roughage. Because larger animals, particularly lions and tigers, require large quantities of food, it is common to find individuals feeding less expensive "homemade" diets: raw hamburger and chicken necks with or without a sprinkle of a vitamin or mineral supplement are typical. These diets may be that are usually poorly balanced. Raw hamburger and chicken necks with or without a sprinkle of a vitamin or mineral supplement are typical. These diets may be poorly balanced and result in severe nutritional deficiencies, particularly in growing animals. Deformities, rickets, nutritional secondary hyperparathyroidism , stunted growth, and other problems are very common in these cases.

Beware of "cheap meat" source diets (usually horsemeat). There have been many reports of pentobarbital residues in some of these diets, sometimes resulting in serious toxicity and some deaths.

Some wild carnivores are quite omnivorous and eat fruits and vegetables on a regular basis as well as a wide variety of meat sources. Supplements can be given in captivity, but should not exceed 10% of the diet. A commercial balanced ration should constitute most of the diet.

Refer to the NWRA's Principles of Wildlife Rehabilitation and the AZA Nutrition Advisory Group online http://nagonline.net/husbandry_chapters.htm for more information.

4. Mammals – Ungulate Nutrition

Many commercial zoo herbivore diets are now available for wild ungulates (e.g. Mazuri). Special commercial diets have also been formulated for llamas and alpacas. Rations for horses, cows, sheep, goats and swine are well documented, balanced and may be suitable for use in non-traditional species. When special diets are not available, feeding wildlife should involve selecting the most closely appropriate model domestic species and proceeding accordingly. For example, horse nutritional guidelines and feedstuffs are appropriate with modification for zebras and elephants, cattle diets for antelope, deer and other ruminants, and swine diets for wild peccaries.

It is important to understand however, that many of these species, so similar to our domestic animals, may have developed requirements specifically adapted to their native environments. Changes in diet through captivity or relocation may result in severe health problems. For example, some animals like giraffe have a natural physiological requirement for browse, while others require particular grasses. It has also been shown that dried hays and grasses commonly fed to our domestic livestock may not contain sufficient Vitamin E for some wild ungulates. Vitamin E related health problems will occur in these animals if supplementation or fresh grasses are not given.

Giraffe feeding
Giraffe feeding

Raising young wild ungulates can be very challenging. Utilization of commercial milk replacers is very valuable, although some modifications may be required to more nearly meet the individual species needs.

Refer to the NWRA's Principles of Wildlife Rehabilitation and the AZA Nutrition Advisory Group online (http://nagonline.net/husbandry_chapters.htm ) for more information.

5. Mammals – Miscellaneous points

5.1. Marsupials

Marsupials span a broad range of gastrointestinal systems and thus nutritional requirements. Many marsupial species have evolved under very specific environmental conditions and very restricted dietary needs. Marsupial mammals in general have a slower metabolic rate than placental mammals and thus require fewer kcal/kg of body mass (KCAL=49xBWkg0.75). Insectivore commercial diets are available from some of the major pet food producers (e.g. Mazuri) and may be used for pet Sugar Gliders.

Recommended Sugar Glider Diet

50% Insectivore diet

50% Leadbeater's Mixture - blend and keep refrigerated
150 ml warm water
150 ml honey
1 shelled hard-boiled egg
25 g high protein baby cereal
1 tsp vitamin/mineral supplement

Treats including meat, diced fruits, bee pollen, worms, insects

(Cathy Johnson Delaney)

5.2. Insectivores

Insectivores have special requirements and can be challenging to feed (see reptiles), although the newer commercial diets (e.g. Mazuri) haveimproved the situation a great deal. Hedgehogs are commonly kept as pets and require a special insectivore diet. They are often fed cat food which is still not high enough in protein content, and too high in fat leading to obesity. Anteaters in a zoo setting will require extra Vitamin K found normally in their ant diet.

Captive African Pygmy Hedgehog (Atelerix albiventris).
Captive African Pygmy Hedgehog (Atelerix albiventris).

5.3. Primates

Primates also have some special dietary requirements. Some primates are leaf eaters and are intolerant of normal primate diets. All primates require a dietary source of Vitamin D3 in the absence of adequate sunlight, and all primates require Vitamin C.

6. Avian Nutrition

In general, little scientific information is available about nutrition in captive birds other than poultry. Many of the same principles used in mammals can be applied to birds. However, birds do possess some unique qualities which make their nutritional requirements different from mammals.

It can be said that birds eat a relatively large amount of food in comparison to their body size. This increased requirement can be attributed to the demands of flight, a continuous athletic activity, and on their increased metabolic rate.

Free-ranging rainbow lorikeets, Trichoglossus haematodus, visit a popular tourist cafe, attracted by the sugar left behind.
Free-ranging rainbow lorikeets, Trichoglossus haematodus, visit a popular tourist cafe, attracted by the sugar left behind.

There are three major stages in a birds life which have a direct impact on their nutritional needs.

  1. Nonbreeding adults: baseline nutritional requirements prevail. Certain periods of nutritional stress increase energy requirements such as during migration, or during seasonal variations with decreased environmental temperatures. Increased protein requirements occur during seasonal molts.

  2. Breeding birds: there are two distinct phases of increased nutritional needs. The first is nest building and egg production. Egg production places special demands on the females need for protein, minerals (especially calcium) and vitamins (especially vitamin D). The second phase is the process of feeding nestlings. Both parents involved in feeding young require extra energy for themselves in order to gather the extra food, as well as specific increases in protein and energy needed for feeding directly to the young.

Growing birds clearly have greater nutritional needs than adult birds. In particular, their protein requirement is significantly higher. Altricial birds (nidicolous birds) are hatchlings which are helpless and featherless and require intensive care by their parents for a number of weeks before they are ready to confront the world. They are normally fed directly by a parent. Pigeons feed their chicks exclusively through regurgitation of "crop milk" during the first week. Crop milk is a special secretion originating in the crop containing 58.6% protein and 33.8% fat. These chicks are weaned onto nearly 100% grain by 2 weeks. Parrots are also altricial birds. Precocial birds (nidifugous birds) are nearly ready to make it on their own as soon as they hatch. They will commonly follow the parent around searching for food. The parent in turn may provide instruction and protection for the young. Ducks are precocial birds.

In general, the avian gastrointestinal system is quite similar to mammals, possessing the same basic organs, and similar enzyme systems. The following enzymes have been found in various species of birds: amylase, maltase, sucrase, lactase, palatinase, lipase, protease, pepsin, trypsin, chymotrypsin, enterokinase, dipeptidase, aminopeptidase, carboxypeptidase, chitinase, and chitobiase. Specific adaptations have evolved to accommodate particular food choices: the beak and mouth, specialized tongues, the crop, the proventriculus, gizzard and variations of ceca.

The intestine itself tends to be relatively short. It is shortest in meat eating birds, and longer in plant eaters. In general, intestinal passage is quite rapid in birds, again allowing for the digestion and efficient utilization of relatively large amounts of food. In the Canada goose, ingested grass is digested and eliminated in 2 hours.

As with mammals, energy requirements can be expressed in kilocalorie requirements (kcal) for maintenance of metabolic functions, body temperature and physical exercise. Smaller birds with faster metabolic rates require more energy per kilogram of body weight than larger birds and thus require more food in relation to mass. This relationship can be expressed by the formulae:

  • Daily basal Kcal requirement = 78 x BWkg0.75 Non-passerines

  • Daily basal Kcal requirement = 129 x BWkg0.75 Passerines

Carbohydrates often provide the most readily available source of energy. These are generally in the form of sugars and starches. Some of the sugars are only minimally digestible by birds, particularly lactose. This sugar, available in milk products, should be limited, otherwise an intolerance and osmotic diarrhea may ensue. Galactose is also toxic to birds if present in amounts greater than 15% of the diet.

Fats can be used directly as an energy source, or are deposited as a future energy source in the storage form of body fat. The essential fatty acids are: linolenic acid, linoleic acid, and arachadonic acid. Animal fats are low in essential fatty acids, where as vegetable fats or oils are high in essential fatty acids.

In the bird, the essential amino acids are: isoleucine, leucine, lysine, methionine, cystine, phenylalanine, tyrosine, threonine, tryptophan, valine, arginine, histidine, and glycine. Glycine is not essential in mammals, but in birds is required for the synthesis of uric acid. These essential amino acids are distributed differently among plant and animal proteins. Plant proteins are deficient in certain essential amino acids, namely lysine, methionine, and tryptophan. These amino acids are available in animal protein sources. Consequently, most birds do require some degree of animal protein in their diets, especially during growth. Some species which are thought of as herbivores actually do ingest animal (usually insect) protein during their growing stage. During this period the parents will actively seek out insects to feed their young, when normally they do not select insects for their own diet (e.g. finches). Even some precocial species will instinctively seek out insects as chicks, while they develop into herbivores as adults (e.g. ducks). It is thought that birds were originally carnivorous or omnivorous, and have developed into herbivores through incidental plant eating associated with insect foraging.

Fiber is felt to be an important part of a birds diet, although no studies have been undertaken to investigate this. In the psittacine, seed hulls provide a fiber source, if swallowed.

Essential Vitamins for Birds

Essential Minerals for Birds

Vitamin A
Vitamin D3
Vitamin E
Vitamin K
Vitamin B1 or thiamin
Vitamin C (for certain passerine birds)
Vitamin B2
Vitamin B6
Vitamin B12
Pantothenic acid
Biotin
Choline
Folic acid

Calcium
Phosphorus
Molybdenum
Iodine
Magnesium
Sodium
Chloride
Potassium
Manganese
Zinc
Iron
Copper
Selenium
Sulphur
Chromium
Silicon
Vanadium
Tin
Nickel

Basic nutrition concepts in birds seem to be similar to those studied in mammals. Much information is available on chickens. There are however, important differences between chickens and turkeys (Gallinaceous birds) and other classes or species. One must remember that chickens have been selectively bred specifically for production of meat and eggs, and the resultant requirements are geared for increasing or maximizing this production. Chickens raised for meat are intended to realize a significant weight gain in a relatively short period of time, without having to live far into adulthood. Consequently, long term studies on the effects of their apparent nutritional requirements are not observed. Laying hens are raised for egg production, involving specific nutritional requirements to maximize egg production. Again they are not intended to live long and healthy lives, but are destroyed once they have outlived their maximum production years. In contrast for example parrots often live very long lives, and longevity is an important factor in their health and nutrition. Consequently, conclusions about general avian nutrition based on poultry nutrition must be made very carefully.

6.1. Feeding Pet Birds (Psittacines)

Parrots are considered omnivores, not strict seed eaters. In the wild, psittacines select a variety of fruits, nuts, seeds, flowers, leaves, and insects. Certain birds will even eat small reptiles, rodents and other small birds. In captivity, we can attempt to provide a "wild type" diet, or can provide a scientifically calculated balanced ration. Unfortunately, bird owners are often misled by bags of food labeled "Parrot mix", thinking that is all they need to feed their pet. There is nothing wrong with feeding a seed based diet to a psittacine, however, seeds are only a small portion of what they really need.

Parrots have very agile and dextrous feet as demonstrated by this Moluccan cockatoo (Cacatua moluccensis) eating her dinner.
Parrots have very agile and dextrous feet as demonstrated by this Moluccan cockatoo (Cacatua moluccensis) eating her dinner.

In general, seeds are low in calcium and high in phosphorus. They are deficient in vitamin A, iodine, and many essential amino acids. They are a good source of energy however. Vegetables and fruits are important components of any psittacines daily ration. They not only provide essential vitamins, minerals, and crude fiber, but are a good source of variety and entertainment in eating. Some fruits and vegetables that are good sources of vitamin A are: cantaloupe, peaches, broccoli, carrots, and collard greens. Legumes are often readily accepted by birds, and offer a wider range of essential amino acids than other vegetables. Peas, black-eyed peas, kidney beans, etc. are well liked. Corn is also readily accepted and is a good source of vitamin A, and methionine.

Pelleted feeds are a sure way of feeding a balanced diet (as far as we know what a balanced psittacine diet is!). Unfortunately many birds do not find pelleted food very interesting, and in some situations, eating is one of the more interesting aspects of the birds day. Because of this, many birds simply won't eat pelleted food unless they are trained to do so as weanlings, or have been very gradually converted to it. With a good deal of patience and persistence, birds can be converted to pellets. In cases where the owner cannot reliably supply a balanced diet, or in an aviary situation, where the convenience and lack of wastage is important, it is worth the extra effort. Commercially available pelleted feeds for psittacines are available from many sources including Lafeber, Purina, Pretty Bird, Kaytee, Zupreem, Harrisons etc. (see beginning of chapter for websites)

Commercially prepared vitamin/mineral/amino acid supplements are very useful, and are necessary when the diet cannot be reliably balanced otherwise. Calcium supplements are given in the form of crushed oyster shell, cuttlebone, egg shells, dairy products and in powdered form. Calcium supplements should always be available, unless the bird is being fed a commercially prepared complete diet.

7. Reptile Nutrition

Feeding and husbandry of captive reptiles is certainly the most challenging aspect in their care and propagation. Reptiles are intimately linked to their environment and have thus developed very specialized niches characteristics which must be satisfied in order to ensure their survival. Our knowledge of most reptile specific requirements for feeding or husbandry is minimal. Consequently errors in these two areas, particularly nutrition constitute the primary causes for morbidity and mortality in captivity. To begin attacking a problem it is absolutely essential that the animal be properly identified and speciated, and that information on natural diet be obtained if available. Once a diet has been chosen strict monitoring of eating habits should be carried out, paying close attention to growth, health and reproduction.

As with birds, many reptiles will change their nutritional requirements through life, corresponding particularly to rapid growth periods, season, food availability, and reproduction.

For simplicity, we can divide reptiles into 4 groups, keeping in mind that each species may have specific requirements beyond this classification:

  • Carnivores

  • Insectivores

  • Omnivores

  • Herbivores

7.1. Carnivorous Reptiles

Carnivorous reptiles are generally easy to feed and rarely develop nutritional problems. This is because they naturally feed on whole prey and it is simple to provide whole prey in the form of whole mice, rats, rabbits, etc. Some species eat eggs and others eat whole birds, while many of the smaller snakes eat amphibians, worms, slugs, etc. It is not a good practice to feed young whole animals (day old chicks or pinkies) as a steady diet. Immature prey animals have poorly mineralized bones and do not contain the appropriate calcium/phosphorus ratio required by the predator species. Feeding whole animals, while simple and complete, is not without problems. There is always a danger of transmitting parasites or other diseases through the food item. Prior freezing while help to reduce this risk. Never use raw skeletal meat (e.g. hamburger, ham, roast beef) as a protein source for the same reasons as stated above: contamination and inadequate Ca:P ratio.

7.2. Insectivores

Insectivores can be challenging to feed. Commercially available crickets and mealworms do not constitute a well rounded diet. Mealworms are extremely fatty and crickets have an excess of chitin which can lead to impactions. Neither has an appropriate Ca:P ratio (mealworms up to 1:9). It is advantageous to offer a variety of insects, including flies and moths, and to supplement with calcium. Diets for crickets can be purchased to " gut load " the animals with calcium and vitamins just before they are fed and thus help counteract the imbalance. Occasionally animals can be converted to a commercial diet although reluctant to eat food that does not move! Cat foods are sometimes used due to their high protein content, however, care must be taken to monitor the fat and potential vitamin imbalance.

For more see the AZA NAG article "Feeding Captive Insectivorous Animals: Nutritional Aspects of Insects as Food" at http://nagonline.net/Technical%20Papers/NAGFS00397Insects-JONIFEB24,2002MODIFIED.pdf

This anole lizard was found on the caribbean island of St. Lucia.
This anole lizard was found on the caribbean island of St. Lucia.

7.3. Omnivores

Omnivores can be fed many different food items, many readily available. Problems arise when too much of any one food is consumed to produce an imbalance. Dog food is often used as a balanced portion of the ration. Care must be taken not to feed too much dog food since the protein, fat and the vitamin/mineral content may be incorrect for the species in question (particularly the vitamin D3 content may be too great). Do not feed cat food. Again, never use skeletal meat alone as a source of protein.

7.4. Herbivores

Herbivores are perhaps the most challenging to feed. They are frequently incorrectly fed an abundance of poor quality vegetables (iceberg lettuce, cucumbers). It is difficult to balance a vegetarian diet. A wide variety of good quality, vitamin rich products must be given. Suggestions are listed at the end of this chapter giving vitamin and mineral contents. Vitamin/mineral supplements are often used along with fresh produce. Care must also be taken not to over supplement with these products. Feeding commercial dog food will result in a variety of nutritional problems for herbivorous reptiles, even though they may readily accept it. Dog food contains too much protein, fat and vitamin D.

7.5. Prepared Diets for Reptiles

There are many commercial diets made for reptiles of different types (Walkabout Farms, Pretty Pets, Zeigler, Mazuri, Zupreem). Some of these food products are of good quality, yet some have been produced with very little research. A good quality product will assist in helping to balance the diet, particularly in the case of herbivores and omnivores. Fresh foods should always be fed in addition to any commercial diet, to help counteract errors in formulation and to provide adequate fiber and moisture. Additional vitamin/mineral supplements should not be given if the diet includes a consistent level of commercial food. This will result in oversupplementation.

7.6. Feeding the Common Iguana

A common iguana eating a plate of mixed vegetables. Note artificial turf substrate and climbing branch in this cage setting.
A common iguana eating a plate of mixed vegetables. Note artificial turf substrate and climbing branch in this cage setting.

Iguanas are very popular as household pets. They are however very difficult to care for and have some special nutritional problems. In the wild, iguanas eat a variety of plants, rarely insects and occasional animal matter to balance their diets. They live in a natural environment with an excess of sunlight and high humidity (depending on the species). Malnutrition is the major health problem seen in the captive iguana. An imbalance in calcium, phosphorus and vitamin D3 leads to stunted growth, pathological fractures, weakness, muscle tremors, tetany and eventual death. In addition, insufficient protein (<22.5%) in the diet of the young growing iguana results in poor growth and general unthriftiness. Unfortunately, the exact requirements for nutrition and management still are not entirely understood. Iguanas seem to have an acute sensitivity to variations in available sunlight and vitamin D3 and the physiology of this phenomenon is still under investigation. In most instances a UVB broad spectrum light source (natural, unfiltered sunlight is preferred) should be provided to assist in vitamin D synthesis. However, this is often not sufficient and oral vitamin D3 must also be given. Oversupplementation with oral vitamin D3 can also occur and is seen regularly, so supplementation must be done with care.

EXAMPLES OF PLANT MATERIALS THAT ARE SAFE AND NUTRITIOUS

adapted from Frye, Fredric L. A practical guide for feeding captive reptiles. Malabar, FL: Krieger Publishing Co., 1991.

Alfalfa: fresh, sun-cured hay, dried leaves, pellets, meal
Apple: fresh, with peel, sliced or grated (discard core and seeds)
Barley: freshly sprouted seeds, freshly grown leaves, sun-cured hay
Beans (several edible varieties: fresh leaves and stems, fruit
Bean sprouts (azuki, black-eyed, garbanzo, lentil, mung, pea, etc.): fresh leaves, stems, blossoms, fruit
Beet: tops, stems, flowers, grated roots
Buffalo grass hay
Cabbage family (kale, napa, broccoli, Brussel's sprouts): do not feed to excess
Cactus: flowers, prickly pears, tender young cactus pads
Carrot: leave, grated root
Clover: fresh, sun-cured hay
Collards: fresh green leaves, flowers
Cotton: leaves, dried or fresh
Cowpea: sun-cured hay, leaves
Crucifers: bok choy, etc.
Dandelion: leaves and stems, flowers, fresh or dried
Dicondra: fresh or sun-cured hay
Eugenia: fresh leaves, fruits
Figs: fresh
Grass clippings: freshly mowed or sun-cured (untreated)
Hibiscus: leaves, flowers, fresh pods
Kudzu: sun-cured hay
Millet: leaves, sun-cured hay
Mint: sun-cured hay
Mixed vegetables: frozen, thawed
Mulberry: freshly picked tender leaves, fruit
Mustard: fresh green leaves, flowers
Nasturtium: leaves, stems, flowers
Okra: fresh, chopped, tender leaves, flowers
Pea: fresh pods, sun-cured hay
Pear: fresh, cut or grated (discard core and seeds)
Peavine: sun-cured hay
Peanut: sun-cured hay with or without nuts
Pelleted commercial chows for guinea pigs and rabbits
Rape: fresh leaves, sun-cured hay
Rutabaga: freshly grated root
Saltbush (winter range): sun-cured hay
Soybean: fresh leaves or sun-cured hay
Squash: freshly grated flesh, blossoms, tender leaves
Stone fruits: peach, nectarine, apricot, plum, etc.
Sunflower: seeds (unsalted) o Timothy: sun-cured hay
Tofu soybean cake
Triticale: freshly sprouted seeds, sun-cured hay
Turnip: fresh leaves, grated root
Vetch: sun-cured Hay
Wheat (soft wheat berries): freshly sprouted, hydroponically grown

Table of Nutrient Content of Some Fruits and Vegetables – ADD LINK TO THIS DOC

8. References and Resources

  • Required Text readings: Small Animal Clinical Nutrition, 4th ed. Hand, Thatcher, Remillard and Roudebush, 2000. Chapters 28, 29, and 30.

  • AZA Nutrition Advisory Group online http://nagonline.net/index.html and http://nagonline.net/husbandry_chapters.htm

  • Bernard, Joni B. and Mary E. Allen. Feeding Captive Insectivorous Animals: Nutritional Aspects of Insects as Food. AZA Nutrition Advisory Group http://nagonline.net/Technical%20Papers/NAGFS00397Insects-JONIFEB24,2002MODIFIED.pdf

  • Crissey,S.D., K.A.Slifka, P.Shumway, and S.B.Spencer. Frozen/Thawed Meat and Prey Items Fed to Captive Exotic Animals: A Manual of Standard Operating Procedures. 2001. U.S. Department of Agriculture, Agricultural Research Service, National Agricultural Library. http://www.nal.usda.gov/awic/pubs/meatprey.pdf

  • Fowler, Murray E. Zoo and Wild Animal Medicine, 5th ed. W.B. Saunders Co., Philadelphia, PA, c2003.

  • Frye, Fredric L. Iguanas: a guide to their biology and captive care. Malabar, FL: Krieger Publishing Co., 1993.

  • Frye, Fredric L. A Practical guide for feeding captive reptiles. Malabar, FL: Krieger Publishing Co., 1991.

  • Harriman, Marinell. The House Rabbit Handbook, 3rd ed. Drollery Press, 1995.

  • Jacobson, Elliott R. Biology, Husbandry and Medicine of the Green Iguana. Malabar, FL : Krieger Publishing Company, 2003.

  • Joosten, Sally and Adele T. Moore. Principles of wildlife rehabilitation: the essential guide for novice and experienced rehabilitators. St. Cloud, MN: National Wildlife Rehabilitators Association, 2002.

  • Koutsos, Elizabeth A., et al. Nutrition of birds in the Order Psittaciformes: a review. Journal of Avian Medicine and Surgery 15 (4) : 257-275, 2001.

  • Robbins, Charles T. Wildlife feeding and nutrition. 2nd ed. Boston: Academic Press, Inc., c1993.

  • Tollefson, C. I. Diets for birds other than poultry. In CRC Handbook series in nutrition and food. Section G: diets, culture media, and food supplements, vol. II. c1977.

  • USDA National Nutrient Database for Standard Reference, Release 18, Nutrient Data Laboratory http://www.ars.usda.gov/main/site_main.htm?modecode=12354500

  • Vohra, P. and Norris, L.C. Qualitative nutrient requirements of birds. In CRC Handbook series in nutrition and food. Section D: Nutritional requirements, vol. 1. c1977.