« Guinea pigs: what to know and how to care » | This article presents tips and elements of veterinary knowledge about guinea pigs. It explains what owners should be aware of when keeping guinea pigs as pets.
Guinea pigs are lively rodents. They originally come from South America where they started to be domesticated circa 1000 B.C. They were used as a source of protein by the Incas. Following the discovery of the Americas, guinea pigs were imported into Europe about 500 years ago, where they have since been used as pets rather than meals. When those little furies benefit from owners with great husbandry skills, they are less likely to become ill or die.
- This blog is intended as a source of general information for pet owners. It does not constitute specific veterinary advice towards a particular medical case. If you are concerned with a particular aspect of your pet’s health, please, book a video appointment to talk with a qualified veterinarian.
Guinea pigs: what to know about them?
Anatomy and physiology
Males and females have a pair of nipples located in the inguinal area (groin). They also show 4 digits on their anterior feet whilst the posterior feet have three digits. Short claws can be observed and might require a trim from time to time.
Guinea pigs’ teeth keep growing throughout their lives, which can bring some mouth problems known as dental malocclusion. They have 20 teeth with the following dental formula (per half mouth): 2 x (2 incisors, 0 canine, 2 premolars and 6 molars).
From their pharynx up to its end, the digestive tract measures 2.3m, on average. It takes approximately 20h for the food to be processed from one side to the other. Guinea pigs are coprophagic animals and they will ingest faeces from their anus many times per day. Older individuals might lose an ability to do so, which lead them to develop faecal impactions. In this case, guinea pigs will require help to relieve the impaction.
Sexing guinea pigs is rather easy. Males have scrotal pouches and the penis can be everted by applying pressure at its base. Females will show a Y shape in the perineal area. Guinea pigs are able to reproduce at 2 months of age for females and at 3 months for males. They are capable to breed the year round.
Gestation lasts between 59 and 72 days (68 days on average). Females won’t make a nest and are usually fast to deliver, with only a matter of minutes between births. They generally produce a litter of 2 to 4 however, numbers can vary between 1 and 13!
At birth, guinea pigs weigh between 45g and 115 g with those under 60g less likely to survive. Females will eat the placenta. Young guinea pigs are born « fully furred », with open eyes and able to stand. It is very important they receive the milk from their mum for 5 days at the very least. Failure to this will result in death of the pups. Weaning will occur at 21 days post birth or when a weight of 180g is reached.
It is possible to foster orphans with a lactating female or by using a formula (4% fat, 8% protein and 3% lactose). If hand-reared, pups can be fed from 12h post birth, every 2h until their 5th day. After 5 days, they can be fed every 4h.
Guinea pigs: how to care for yours?
Behaviour, housing and feeding
Guinea pigs are social by nature and they will tend to look for physical contact with their peers. They will gather in small crowds but won’t groom each other.
They can exhibit aggressive behaviour by pulling their mate’s hair or nibbling ears, especially when stressed or their enclosure is too crowded.
If they are used to be handled by people very early in their lives, they will become great pets. Although, the major particularity of guinea pigs is the way they respond to a stressful situation: « freeze or flight ». This means that when facing danger or scared, they will either remain immobile or swiftly escape, which can prompt some problems or accidents.
Those small rodents tend to be vocal and literature has identified a series of recognisable sounds:
When planning to house a guinea pig, one should bear in mind they will produce a significant amount of faeces. They will tip unstable things over, such as food/water containers and they have a tendency to be « a bit messy », defecating about everywhere.
The minimal amount of available space for an adult pet guinea pig should be 1,300 square cm. They can be housed in plastic or metallic cages with side panels of at least 25cm in height. However, since they don’t climb or jump, the box does not necessarily need a rooftop. Because wire mesh can cause leg injuries, it is recommended to use a plain material for flooring.
Bedding can be made up of either cellulose fibre, shredded newspaper, wood shavings or straw. Guinea pigs should be housed at a temperature ranging from 18 to <24 degree celsius. Their enclosure should be placed in a quiet, adequately ventilated environment, away from direct sunlight. They will tolerate cooler temperatures better as they can easily suffer from hyperthermia. Hence, it is recommended not to keep them in areas with high temperature and humidity.
Their living space should be kept very clean and the bedding must be changed regularly to prevent ammonia levels from rising, with potential to cause all sorts of complications.
Guinea pigs will form their « judgement » about food very early in their lives. Hence, they could later refuse to eat anything they have not been used to. This can cause them to refuse new food and to become anorexic, which will be dangerous. To avoid such potential threat to their future wellbeing, it is recommended to get them accustomed to a variety of foods when they are still young.
Guinea pigs are strictly herbivorous and require a minimum level of crude fibre of 10% and between 18% to 20% of crude protein depending on life stages (growth, lactation). They are dependent on external sources of vitamin C because they are deficient in the enzyme called L- gluconolactone oxidase. Therefore, when kept as pets, owners must ensure vitamin C is provided at a daily rate of 10mg/kg per adult. Pregnant, lactating and growing individuals must receive daily vitamin C rates of 30mg/kg.
Therefore, guinea pigs will need to be fed a diet taking their specific requirements in consideration. Ideally, they should receive a combination of guinea pigs pellets (18% – 20% crude proteins; 10% – 16% fibre, fortified with vitamin C), high quality grass hay available at all times and a handful of fresh greens. Fruits and dry cereals, if offered, should be considered more a small treat than the basis of the diet. All fresh vegetables and fruits must be properly washed before being offered. They must be removed from the enclosure within a few hours if they have not been eaten.
It is worth noting several points about vitamin C:
- in pellets, 50% of the initial quantity of vitamin C might disappear 90 days after opening, hence it is best to purchase a diet with stabilised vitamin C
- red and green peppers, broccoli, tomatoes, kiwi and oranges are rich in vitamin C
- kale, parsley, beet greens, chicory and spinach are rich in vitamin C but also in calcium and oxalates, hence they are best offered in very limited quantities
- vitamin C can be added to drinking water at a concentration of 1g/L; however, within 24h 50% of the vitamin C will have disappear, especially in an open container
- water must be changed daily as to make sure the vitamin C content is fully preserved for the benefit of the guinea pig
Guinea pigs: what could make them sick?
Conditions affecting guinea pigs (non exhaustive list)
Please, bear in mind that sick guinea pigs are less able to cope with veterinary procedures and/or visits to the vets (i.e.: being transported and handled). They could easily go into respiratory or cardiac arrest, hence the greatest caution is needed when dealing with them in such context.
Those diseases are rather common and possibly the major causes of why guinea pigs might become unwell.
Conditions affecting the digestive system are most of the time related to teeth and the composition of the diet guinea pigs receive. Vitamin C and fibre deficiency, as well as infection and trauma, are reasons why teeth tend to show malocclusion.
Owners and veterinarians should seek to investigate guinea pigs’ mouths during checks because problems with those can be the cause of other health issues involving the digestive tract.
Other conditions of the digestive system involve gut stasis, enteritis, diarrhea, enterotoxemia (associated with oral consumption of antibiotics; or due to a problem with the gut flora), fecal impaction, hepatic lipidosis (secondary to anorexia) and cancers.
Important: a guinea pig who stops eating must be considered a matter of veterinary emergency.
Guinea pigs are very sensitive to respiratory infections. They will catch those especially if their environment is not properly ventilated or if the air becomes polluted.
To avoid infectious respiratory diseases (bacterial and viral pneumonia) in guinea pigs, it is recommended to use bedding made of paper rather than wood chips, due to the release of particles in the air.
A list of non-infectious respiratory diseases is provided as follow in relevant literature: foreign body inhalation, choke, bloat, molar malocclusion, thoracic trauma, electrocution, pulmonary adenoma.
Urinary and reproductive diseases:
Guinea pigs can suffer from urinary calculi and urinary tract bacterial infections. Calculi can be found in the urethra, bladder or even in kidneys, ureters and other less common places of the genital and urinary system.
A diet rich in pellets and low in fibre and low variety of fruits and vegetables is understood to trigger such troubles. Pellets containing alfalfa and calcium may also promote the formation of urinary calculi.
Affected guinea pigs can show troubles to urinate, urine might have blood in it. The guinea pig might stop eating or show signs of pain. They will need to be seen by a veterinarian.
Other conditions involving the urinary and reproductive system are listed below:
- nephritis, renal cysts, kidney failure
- ovarian cysts, prolapse of the uterus, troubles giving birth
- toxemia during pregnancy, mastitis, metritis, pyometra
Important: « scrotal plugs » are made of a mix of soiled bedding and secretions which stick to the genital area of the guinea pig (male or female). If left unattended, these plugs can result in secondary infections. Thus, guinea pigs will need particular attention and husbandry care as a matter of prevention.
Among the most common conditions affecting the skin: ringworms such as Trichophyton mentagrophytes and external parasites such as mites, lice and Demodex (rarely).
Although ringworms tend to be diagnosed with a Wood’s lamp (fluorescence), T. mentagrophytes does not behave in such ways. Hence veterinarians will offer other methods for diagnosis (fungal culture) when they suspect ringworm infections in a guinea pig.
Another skin condition commonly seen in guinea pigs is called pododermatitis. This will occur due to inappropriate bedding such as it is abrasive or not clean, leading to inflammation and swelling of the skin under the feet. This will give room for infection to develop, which can equally lead to a series of severe conditions as a butterfly effect. A deficiency in vitamin C could also be the root cause of the condition. Obesity does not help as well, hence, as a matter of prevention, it is strongly advised to provide a proper diet, a clean and suitable environment as well as monitoring the guinea pig’s weight.
- Ringworms and certain mites can potentially be passed to humans (zoonoses). They also tend to be difficult to entirely eradicate from the environment, hence the problem might come back.
- Affected guinea pigs can appear to their owners as to have a seizure whereas they are undergoing intense scratching from parasites. This can lead to serious trauma and secondary skin infections. So, they must be seen by a veterinarian to be diagnosed and treated asap.
- Severe cases of pododermatitis might lead to the death of the animal, hence prevention through good husbandry is mostly recommended.
Muscular and neurological diseases:
Because of a genetic mutation, guinea pigs are unable to synthesise their own vitamin C. This is why it is vital they get it directly from the food they eat. Vitamin C is critical for the formation of type IV collagen which is involved in the proper functioning of organs of the body.
For example, without collagen, teeth become wobbly and impair the proper feeding of the animal. Blood vessels are also affected by lack of collagen and this lead to haemorrhage. Signs might start to develop within 2 weeks of vitamin C deficiency.
Guinea pigs can also suffer from osteoarthritis and other less reported musculoskeletal conditions. Those are generally understood to be related to issues with vitamins and minerals and husbandry problems.
Eye and other diseases:
Guinea pigs can suffer corneal ulceration, most often secondary to trauma. They also commonly present with conjunctivitis which is the result of infection or a deficiency in vitamin C.
Chlamydophila caviae is known to cause guinea pig inclusion conjunctivitis (GPIC). Symptoms will appear mild to severe. This disease is listed for its zoonotic potential, which means it could be passed to humans interacting with guinea pigs. Some guinea pigs might host the pathogen whilst showing no symptoms. Additionally, presence of Chlamydophila caviae has been reported in a cat, his owner and in rabbits.
It is worth noting guinea pigs are sensitive to high temperature. They can develop heat stress in temperature of 24 degree celsius when housed outdoors. Heat stress can send them into coma and they may die despite supportive treatments to cool them down.