Guinea pigs are natural herbivores, who would spend their time foraging and grazing in small herds in the wild. Their teeth are continuously growing, which is one of the reasons why they need plenty of roughage to chew; this wears down their teeth and helps prevent serious dental problems. Providing sufficient fibre in their diet is also very important for both their gastrointestinal system and general health.

For your guinea pigs to be happy and healthy, they need plenty of the following in their diets:

• A constant supply of grass and/or grass hay (such as Timothy, Oaten, Barley, or grassy hay). Guinea pigs should not be fed Lucerne (alfalfa) or Clover hay, as these are too high in protein and calcium. The hay that you fed should be available 24 hours a day and of good quality, dry, and sweet smelling. The hay should ideally be contained in a hayrack or basket to prevent it sitting on the enclosure floor and getting contaminated by your guinea pigs’ waste and becoming damp, dirty, and mouldy; this is unhygienic and could make your guinea pigs sick.
• Fresh leafy green vegetables & herbs should be fed daily. Some examples of these include bok choy/other Asian greens, dark leafed lettuce varieties, dandelion greens, snow peas, and herbs such as marjoram, borage, marigold, nasturtium, rosemary, parsley, coriander, basil, and dill. Other foods that are good to fed guinea pigs a few times a week include broccoli, cabbage, celery, endive, carrot tops, brussel sprouts, kale, silverbeet, mint and fruits such as apples (no seeds), mango, and papaya.
• A dietary source of Vitamin C because (like humans), guinea pigs cannot synthesize Vitamin C from other food substances. This is usually supplied sufficiently by the fresh leafy green veggies, but it is safer to supplement this with Vitamin C rich foods such as turnip greenss, mustard greens, green, orange, and red capsicums fed daily. Foods like carrots, kiwifruit, berries, and pineapple are also great as a source of Vitamin C and a tasty treat for your friend but only fed them a few times a week, not every day as they have quite a high sugar content.

Make sure that you source grass, herbs and vegetables that have not been sprayed by any chemicals, as these could harm your guinea pig. Lawnmower clippings should never be fed to your guinea pig as these can cause gastrointestinal blockages that can make your pet very sick.

High quality commercial ‘Guinea Pig’ pellets (minimum 16% fibre content) may be offered in small quantities, but these should not form the main part of the diet. Although many contain adequate levels of Vitamin C, this is only when it is very fresh and within just a few months these foods no longer contain Vitamin C.

Guinea pigs must have access to clean fresh water at all times.

Uneaten food should be removed from your guinea pig’s enclosure after a few hours to ensure that these don’t rot or become moldy and harm your guinea pig.

It’s important to also know what not to feed guinea pigs, as there are plenty of items that might seem harmless but can in fact cause significant health issues. Make sure you do not feed your guinea pigs the following foods (this is not an exhaustive list): cereals, grains, nuts, seeds, corn, beans, peas, buttercups, garden shrubs (such as hemlock or privet), lilies of any kind, sweet peas, nightshade, oak, avocado, onion grass, onions, potato tops, beans; beetroot, mushrooms, daffodils, foxglove, rhubarb leaves or human foods such as breads, biscuits, sweets, sugar, breakfast cereals, dairy products, chocolate, pasta, crackers, or pickled foods.

If you need to change your guinea pig's diet, please make sure you introduce any changes gradually over a few weeks.