Gerbil Food Supplements

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Food that can supplement the main staple diet

When supplementing the various commercial mixes a wide variety of foodstuffs are available

Bird feed

These can include various bird foods, especially those that contain smaller seeds, such as a foreign finch, canary or budgie mix. Other suitable bird foods to add in small quantities are racing pigeon mix, high protein chicken feed for egg layers, Cockatiel mix or Parrot mix. A good birdseed mix is usually a good place to start for homemade mixes because gerbils by nature are natural seedeaters.

 Horse feed

Food for horses can be used too. These usually consist of rolled oats, corn, barley and Alfalfa. They can be bought either mollassed to make them sweeter tasting or without molasses added. However it's wiser to opt for unmollassed versions of the feed.

High protein food supplements

Egg biscuits or dried cat or dog foods can also be used for young or breeding animals to increase the protein content and to ensure they get an adequate mineral content in the diet. Alfalfa is also very high in protein and calcium. It should be noted though that % values of alfalfa would be lower than on the packet because the very high fibre content binds some of the protein and calcium, so values after ingestion are much lower.

Nuts and seeds from health shop outlets

There are simply dozens of nutritious nuts and seeds available from these sources or some of the larger supermarkets. Don't feed any salted or roasted nuts but opt for nuts in their raw state. Hazelnut, pistachio, cashew, walnut, peanut, Brazil nuts and pine nuts can all be offered safely in small quantities for your gerbils. Seeds such as pumpkin and sunflowers are also regarded as treats and are extremely nutritious. With shelled nuts it's often best to crack the shells to start them off, then scatter them around the tank. This in itself is good practice, as it promotes foraging behaviour in the gerbil.


Kashi Cereal

Kashi is recommended as a healthy breakfast cereal for humans, and is greatly enjoyed by gerbils too. It consists of puffed cereals such as soy, and looks similar to rice crispies or sugar puffs, minus the sugar. It is fairly high in protein and is an excellent food to add to regular feed.

Fresh or freeze dried insects

Some gerbils will eat insects when they are available; the same goes for their wild cousins, as it offers them a source of moisture and nutrition. However saying this, their nutritional values are quite neglible. Water content is around 50% of bodyweight, and larvae types have a very high fat content and protein is around 5% for earthworms to around 10% for crickets, Regarding vitamin contents this can vary dramatically from species to species, for example earthworms have extremely low values of vitamin E, where as waxworms are much higher, however things like vitamin A are negligable throughout most live foods offered. Also calcium concentrations are usually very low in insects and larvae, and there is nearly always an imbalance in calcium:phosphorous ratios, with one exception which is the pinhead cricket.

As for trace elements usually there are sufficient concentrations of copper, iron, magnesium, phosphorous and zinc to meet requirements of mammals, but things like supermealworms and waxworms contain extremely low amounts of magnesium.

If you do decide to offer your gerbils live foods, certain precautions should be taken.  Care should be taken to not feed bugs that have died in the storage containers, especially mealworms as this can pose a health risk. Also, because of the way in which mealworms and other insect larvae are produced, there can be the usual risks of Salmonella and E.Coli present. Also its best to feed mealworms supervised in a deep bowl, as often they will escape, then burrow under the shavings and can emerge later as large beetles. The safest way to go is to use freeze-dried insects, they are fairly nutritious and are less messy to use.

I personally don't feed live foods to Mongolians, but freeze dried food and also insectivorous bird feed is used to feed some other smaller gerbil species throughout the early spring, summer, and autumn months, but I omit this practice during the winter months.

Fresh fruit and vegetables

Other supplements that are commonly fed to gerbils are fruit and vegetables, and we often include a weekly/fortnightly feed of small portions of either fruit or vegetables. Fruit and vegetables can be wide ranging, but I must stress that both fruit and vegetables must be given as treats and in small quantities. What we should remember is that fruits from plants would only be available to gerbils towards the end of the season. Greenstuffs from several plants (see wild staple diet) are usually available to them from spring onwards, It is only in captivity and through human intervention that they are available on a year round basis. So it would be wiser to feed greenstuffs till say august and include fruit supplementations towards the end of the season. In this way we could roughly mimic their natural wild diet.

Toxic potential of fruits and vegetables

In small portions the various fruits and vegetables present little risk to gerbils or rodents in general, but overuse or chronic use can easily lead to problems. We must bear in mind that several foods, which we avoid giving our gerbils, such as onions, and plants high in Oxalic acid etc, are present in their wild habitat and are consumed by them. Allium (onions and garlic families)* species are prevalent in their wild habitat, and are most probably part of their wild diets, as are plants species such as Atriplex and several plants from the Chenopodiaceae family, which are very high in Oxalic acid. However Allium species are bulbs and as you know, take a full season for the bulb to develop and aren't usually lifted till autumn, so the percentage of these foods in their wild diet would be extremely small or restricted only to their leaves. Gerbils have probably developed a high tolerance to plants high in Oxalic acid and some species such as the fat sand rat (a specialised leaf eating gerbil) consume huge quantities of plants such as Atriplex halimus which is very high in Oxalic acid.

* Dogs and cats are sensitive to plants from the Allium family and can easily develop haemolytic anaemia if they eat enough onions or garlic. This goes for both cooked and fresh portions of the bulb.

What a lot of people fail to realise is that all fruit plants and vegetables produce naturally occurring pesticides to help them against insect attacks. And much research has gone into the potential carcinogenic effects of synthetic and naturally occurring pesticides on rodents, and the data is freely available if you search for it.

Dr. Lois Swirsky Gold is Director of the Carcinogenic Potency Project at the Environmental Health Sciences Centre (NIEHS), University of California, Berkeley, and a Senior Scientist at the E.O Lawrence Berkeley National Laboratory. She has published 110 papers on the methodology of risk assessment, analyses of animal cancer tests, and the implications for cancer prevention and regulatory policy. Her Carcinogenic Potency Database (CPDB), analyses the results of 5500 chronic, long-term cancer tests on 1400 chemicals. Dr. Gold's work has addressed many vital issues in the field of risk assessment. What I present here is only a glimpse into the vast amount of research that has been conducted on rodents to establish potential toxic dosages, or dosage levels that are known to cause cancers in rodents.

A common misconception is that substances if they are naturally occurring are safe; this has been shown many times not to be true. Many medicinal herbs that were once thought to improve health have recently been shown to be quite hazardous to humans. Since most of these carcinogenic tests are conducted on rodents to find their LD value (lethal dosage) we should really take note of this research. A huge proportion of these potentially dangerous chemicals that humans are exposed to on a daily basis occur naturally.

In humans the exposure to natural pesticides (the chemicals that plants produce to defend themselves) is 1500 mg daily; in comparison, the total daily exposure to all synthetic pesticide residues combined is 0.09 mg; thus, 99.99% of the pesticides humans ingest are natural.

Since the toxicology of natural and synthetic chemicals are similar, one expects and finds, a similar positivity rate for carcinogenicity among synthetic and natural chemicals.

This research has shown that humans are probably 'living in a sea of naturally occurring rodent carcinogens' as defined by these tests conducted on rodent populations.

Data from research shows that although only a small proportion of natural pesticides in plant foods have been tested, the 37 that are rodent carcinogens among the 71 tested occur in more than 50 common plant foods. It is probable that almost every fruit and vegetable in the supermarket contains natural pesticides that are potentially carcinogenic to rodents

A common argument is that these naturally occurring pesticides are safer because they are part of human evolutionary history, and mechanisms have evolved to cope with these naturally occurring chemicals. This assumption has been proved false many times in these rodent carcinogen tests, and that toxic hazards are similar for natural or synthetic chemicals. The general public also tends to view chemicals as being only synthetic, and to think of synthetic chemicals as toxic; however, virtually every natural chemical will be toxic at some dosage.

It must also be remembered that gerbils and rodents that have been domesticated, have not had no where near enough time to evolve any sort of 'toxic harmony' with many of the newer fruits and vegetables that are now becoming more widely available on supermarket shelves, and wouldn't be present at all in their natural environments. Once in captivity the staple rodent diet has changed markedly along with their recent domestication. Indeed very few of the plants and fruits given as treats, like banana chips, dried peas, corn, and many other vegetables and fruits would not be present in their native staple diets. Therefore natural selection works far too slowly for these rodents to have evolved any specific resistances to the food toxins present in these newly introduced plants.

Another thing that we should bear in mind is that when humans grow these plants on crop land, is that no plot of land is immune to attacks from insects, so plants need chemical defences (plus often synthetic chemicals are sprayed) to survive any pest attacks. Plant breeders work hard to develop new strains of plants to be more and more insect resistant, this basically means that they are being bred to contain a much higher percentage of natural plant toxins. The potential hazards of this are obvious. A good example of this recently includes a strain of newly developed highly insect resistant celery, and people who harvested it developed severe rashes when they were exposed to sunlight. It was found out that this pest resistant celery contained 6200 ppb (parts per billion) of carcinogenic and mutagenic chemical called psoralens instead of the 800ppb present in common celery.

Below is a list of all the known naturally occurring carcinogenic toxins present in plants, all of which were ascertained by testing on rodents.

Carcinogenicity status of natural pesticides tested in rodents (Fungal toxins are not included)

 We must remember though that all these were given in specifically high dosages to establish lethal dosages or dosages that will eventually cause cancer in rodents. Mammals have many natural body defences that buffer against normal exposures to toxins and these are usually general, rather than tailored for each specific chemical. Thus they work against both natural and synthetic chemicals. The same could be said for rodents. General defences of mammals include the continuous shedding of cells exposed to toxins, these include the surface layers of the mouth, oesophagus, stomach, intestine, colon, skin and lungs and these cells are discarded every few days; DNA repair enzymes, which in return repair DNA that can be damaged from a whole host of many different sources. Detoxification enzymes are also present in the liver and other organs, which generally target groups of chemicals rather than individual chemicals. These defences of mammals are usually general, rather than specific for each chemical and this in itself makes good evolutionary sense. The reason that herbivores or even omnivores evolved general defences to toxins is presumably to be prepared to counter a wide ranging and ever-changing array of plant toxins in an evolving world. For e.g. if a herbivore had defences against only one specific type of toxins, it would be at a great disadvantage in obtaining new food when favoured foods became scarce or unavailable, or if plants evolved new chemical defences.

So does all this data present mean we should studiously avoid fruit and vegetable supplementation for our rodents? Well of course it doesn't! The obvious benefits of vitamin, minerals, etc, far outweigh the potential dangers from their use. They should be regarded as food supplements. What it does indicate though is that over use of single foodstuffs and indeed a high intake of certain foodstuffs can indeed present problems long term for them. Another thing to bear in mind is that we shouldn't always be on the look out for strange exotic fruits and vegetables. All too often on forums I see 'will ugli fruit, star fruit, etc, etc, be ok for my gerbils?' Although here I must say if it's generally all right for humans to eat it will be ok for rodents. But the truth of the matter is that often very little research has been conducted into the toxic potential of these newer fruit and vegetable introductions. A rule of thumb is stick to trusted fruit and vegetables that have been used for small mammals since their domestication. A 'suck it and see' mentality may prove disastrous to your animals if no research is available on the newer fruits or vegetables in question. A holistic approach to diet should always be employed, and should always be diverse, but also well balanced, and this should include vegetables as well as fruit. They key word that should be employed is moderation.

Dried fruit and vegetables

These can be varied and are enjoyed by gerbils in small quantities. Sultanas, raisins, banana chips, apple, apricots etc, are readily eaten when in their dried state. They are sweet tasting and high in simple sugars, and who doesn't like a nice treat now and again! My own gerbils particularly like dried apricots. Vegetable flakes such as carrot, peas, and beetroot are also very much appreciated and are available in many commercial rodent mixes. Again they key word is moderation and remember once fruit is dried it is effectively concentrated, so at all times use common sense and give in gerbil sized portions.

Citrus fruit

A lot of sources do not recommend citrus fruits, but in small treat like quantities they will do no harm, and especially so if given dried. That is providing the gerbil actually like them! The high water content of citrus fruits could cause loose stools, but if it were dried fruit it would be more preferable. Again though remember a gerbil size portion is very tiny, so if it actually likes it, a small portion once a week or fortnight would do no harm.


Peas, beans and lentils are known as pulses. They are the seeds of plants belonging to the plant family Leguminosae, it's name originating from the characteristic pod or legume that protects the seeds while they are forming and ripening. With approximately 13,000 species, the family Leguminosae is the second largest in the plant kingdom. They can be eaten fresh or dried and come in a wide range of varieties with a range of colours, flavours, and textures. The well known peanut or groundnut is also a legume rather than a nut. All pulses, except for Soya beans, have a similar in nutritional content. They are very rich in protein, carbohydrate and fibre, and also low in fat, which is mostly of the unsaturated kind. They are also important sources of some B vitamins. Fresh pulses contain vitamin C, but this declines after harvesting and virtually all vitamin C is lost from dried pulses. A lot of pulses have to be cooked thoroughly before use, but many such as green peas or green beans are perfectly safe to eat raw.

 Kidney Beans and related Beans

Contained in kidney and similar related beans, is a toxic agent known as Phytohaemagglutnin or Kidney Bean Lectin. However it is in kidney beans where the highest concentration is found (Phaseolus vulgaris). The unit of toxin measure is the haemagglutinating unit (hau). Raw kidney beans contain from 20,000 to 70,000 hau, while fully cooked beans contain from 200 to 400 hau. White kidney beans, another variety of Phaseolus vulgaris, contain about one-third the amount of toxin as the red variety. Broad beans (Vicia faba) contain 5 to 10% the amount that red kidney beans contain.

As few as 4 or 5 beans can bring on symptoms, and symptoms vary from between 1 to 3 hours. Onset is usually marked by extreme nausea, followed by vomiting, which may be very severe. Diarrhoea develops somewhat later (from one to a few hours), with accompanying abdominal pain.

Lima Beans*

Lima beans are known to contain cyanide compounds, which is why many countries, including the America, restrict commercially grown varieties to those with very low cyanogen levels. However the lima beans grown in Java and Burma have 20 to 30 times the concentration allowed in most Western countries. They must be cooked very thoroughly to allow the hydrogen cyanide gas produced to be driven off.

* see cyanides in plant species.

Soya Beans

In their raw state these contain an anti-trypsin factor (or trypsin inhibitor), which prevents the assimilation of the amino acid Methionine. Soya beans require careful lengthy cooking to ensure destruction of this inhibitor. They should be soaked for at least 12 hours, drained and rinsed then covered with fresh water and brought to the boil. Soya beans should be boiled for the first hour of cooking. They can then be simmered for the remaining 2-3 hours that it takes to cook them. Other Soya products (e.g. tofu, tempeh, soya milk, soya sauces and miso) are quite safe to use. Soya beans can also be sprouted, but the sprouts should be quickly blanched in boiling water to inactivate the trypsin inhibitor.

Sprouting Beans & seeds

Many whole pulses for example, aduki, chickpeas, whole lentils, marrowfat peas, mung and soya beans) can be sprouted which increases their nutritional value. Various seeds contained in a gerbil mix can be sprouted as well, and can be a nice treat once they have been thoroughly washed to occasionally added to their diet.


As an owner of gerbils, if you insist on using herbs or herbal remedies, you must remember that many haven't been tested for toxicity or carcinogenic potential, and as such should be treated with some caution. Many though are well known by homeopathic vets, and are approved for use in small quantities for animals. However some well known ones have recently been shown to have just the opposite effect.

Comfrey is a medicinal herb that is carcinogenic in rats. Formerly, it was recommended for well-being, but currently the PDR (Physicians Desk Reference) for Herbal Medicines indicates: 'One should entirely forgo internal administration of the drug [comfrey], due to the presence, however small, of pyrrolizidine alkaloids which have hepatotoxic and carcinogenic effects. It has been determined that traces of the alkaloids present a danger.'

Poisoning epidemics by pyrrolizidine alkaloids have occurred in the developing world. In the U.S A, poisonings, including deaths have been associated with use of herbal teas containing comfrey. Pyrollizidine alkaloids reportedly reduce taurine, (which is needed in the diet by animals such as cats) which is a hepato-protective chemical; therefore, individuals who are low in taurine (e.g. vegetarians, since taurine is present in meat but absent in vegetables) may be at greater risk of poisoning from pyrrolizidine alkaloids, and has been mentioned is also a known rodent carcinogen.

Coltsfoot Has been shown to be a liver carcinogen in rats. The PDR for Herbal Medicines cautions that the pyrrolizidine alkaloids in flowers are possibly hepatotoxic and carcinogenic. Also the above list includes several well-known herbs such as Basil that are known rodent carcinogens.

Dandelion, Yarrow, Horsetail & Whitethorn  All of these plants contain contain Caffeic acid. This is a secondary plant metabolite and has no relation to caffeine, but has been recently reported in studies to cause cancer in mice. Caffeic acid was tested for carcinogenicity by oral administration in mice, where it produced renal cell adenomas in females, and a high incidence of renal tubular cell hyperplasia in animals of each sex. Studies show that in rodents, their intestinal bacteria may alter the formation of these metabolites of Caffeic acid which leads to these problems. Dandelion is also a well known diuretic, so much so that Dandelion root is a registered drug in Canada.  This in effect will cause a much increased frequency of urination, which to a gerbil may prove to be deleterious to their long term health as the animal has evolved highly efficient kidneys to conserve water.

White & Red Clover  White clover has high volumes of Prussic acid (cyanide) in it. This is made worse in lawn conditions as it increases if its been cut or trampled on. White clover has caused fatalities in cattle, so in gerbils poisoning would occur with a much lower dosage.  Red clover (and white clover too) often carries a leaf fungus known as black patch fungus that causes “slobbers” in horses causing excessive dehydration in the animal.

However some weeds/herbs from the garden can also be used as a treat, but be careful you don't pick these from roadside verges and from places such as municipal gardens, play parks, etc, as these can be tainted with exhaust fumes and toxic pesticides may have been sprayed on communal garden displays, parks, etc. It should also be noted that all fruit, vegetables and herbs, etc should be thoroughly washed and anything left uneaten should be removed after an hour or so. This is because if left to their own devices, gerbils will bury the food and in a short time it will become mouldy and a potential reservoir for harmful bacteria and fungus.


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