Can Guinea Pigs Eat Grass? (From Outside, Cat Grass, Wheatgrass…)

Guinea pigs typically eat a diet rich in fiber and forage that includes hay and a variety of vegetables. Piggies are natural herbivores whose ancestors grazed exclusively on forage all day including herbs, weeds, and fresh and dried grasses. So does this mean that pet guinea pigs also thrive on fresh grass found outside?

Generally, guinea pigs LOVE to eat fresh grass and it’s a very natural part of their diet. Guinea pigs can eat many varieties of grass from outside in your yard or grown indoors. However, there are a few things you should know first.

Some of the grass that grows in our modern society is exposed to potential hazards not seen in the wild where our piggies originated. For this reason, it’s important to be vigilant about where you pick grass for your guinea pigs.

Additionally, it’s important to transition your guinea pig gradually if they are not accustomed to eating fresh grass. I’ll weigh the benefits and drawbacks of feeding grass to your furry potatoes below.

TJ and Willow love grazing outside together.

Can You Pick Grass For Your Guinea Pig Outside?

As mentioned above, you can absolutely pick grass for your guinea pig outside, in addition to other guinea pig safe plants such as plantain, dandelion, and clover. However, there are a few things you should know first!

First of all, it’s crucial to pick grass by hand or using scissors only. Mowed grass clippings from a lawnmower ferment and rot quickly in your guinea pig’s stomach, which can cause bloat. They are also mixed with lawnmower fuel which is dangerous for your little potato.

Pick healthy grass that is fresh and green, and shows no signs of mold. Also avoid feeding soggy or wet grass, as this can rot or mold more quickly after picking.

Grass that grows earlier in the season is often sweeter and more nutrient-rich than grass that grows later in the year. Guinea pigs usually love the new growth the most, but it’s also the most likely to cause stomach upsets if it’s fed too much or introduced too quickly.

Fresh grass and dandelions from outside are much appreciated by most piggies!

It’s crucial to choose an area to pick grass that is completely untreated and free from fertilizers, pesticides, herbicides, and other chemicals. All of these are very toxic to guinea pigs and can make them seriously ill or worse. Also, choose an area that has not been soiled by dogs or livestock as this can be toxic to guinea pigs as well.

Avoid boulevards or areas near busy roads that are frequented by pets, or are often exposed to fuel residue from vehicles. It’s also best to avoid any public areas or parks unless you know for certain that they are not treated in any way.

Grass roots are generally safe for guinea pigs, but they are more likely to be contaminated with bugs and dirt, so it’s best to clip just the grass for your guinea pigs and leave the roots in the ground. It’s also a good idea to rinse and pat the grass dry before feeding it to your guinea pig to remove any traces of dirt or small insects.

Can You Take Your Guinea Pig Outside to Graze?

Another way to feed your guinea pig grass is to take them outside to graze themselves while enjoying the fresh air and Vitamin D from the sunshine. Guinea pigs make great little lawnmowers and it’s good for them to get outside. Most guinea pigs are nervous the first few times they go outside, but they soon relax once they realize it is safe and there is so much yummy grass to munch on.

If you take your guinea pigs outside to graze, ensure that they’re in a safe enclosed space like a run or an exercise pen. You can also put a cage top over them and move it around periodically so they can mow down different areas of the lawn.

A run with an enclosed top is ideal to ensure that your guinea pigs are safe from birds of prey. Guinea pigs can slip through small areas quickly and escape from a yard, so it’s always a good idea to set up their own safe enclosure.

However, an open-top ex-pen also works if you are sitting inside with them and supervising very closely. It’s not unheard of for large birds to swoop down and try to grab a guinea pig even with humans near so please be extra vigilant with your piggies.

Willow grazing on grass and some piggy-safe weeds outside in her secure ex-pen.

Other predatory animals like dogs, cats, raccoons, and rats can also pose a risk, so ensure that your piggies are fully supervised at all times when they are outdoors.

Choose a quiet spot to set up your guinea pig run where your guinea pig will be out of direct sunlight or have easy access to shade. If this is not possible, you can create shade by draping towels over part of the run or setting up a barrier to block some of the direct sun.

It’s a great idea to let your guinea pigs out to enjoy the fresh air and sunlight while they graze, as long as the weather is nice for them.

If your yard has any gardens or unsafe weeds or plants, set up your outdoor run a safe distance away from them so your guinea pig can’t eat anything toxic. Additionally, be sure to rake up any mowed grass clippings, unknown leaves, or nuts if there are any on the ground.

Also, ensure your guinea pig has a hiding place while they’re outside in case they get spooked or nervous about something. I like to bring my piggies outside using a soft-sided carrier so they are safe and secure while being carried out. The carrier also gives them a nice place to hide outside if they get scared.

Additionally, it’s important to make sure the temperature is at a comfortable range before taking your guinea pig outside so there is no risk of them catching a chill or suffering from heat stroke. Guinea pigs are most comfortable between 60-85 degrees Fahrenheit.

Also, check the ground temperature by placing your hand on the ground. Guinea pigs are very small and low to the ground, so it’s important to ensure the ground temperature feels comfortable for them before letting them out to run around.

How Much Grass Can Guinea Pigs Eat?

Guinea pigs can eat fresh grass every day as long as it’s been introduced gradually into their diet. If your guinea pig eats large amounts all at once without adapting to it first, it can potentially cause an upset stomach, diarrhea, or other gastrointestinal issues.

For this reason, it’s a good idea to start with a small handful of grass or 10 minutes of grazing at first. Monitor for any digestive upset, abnormal stools, or unusual behavior after adding fresh grass to their diet.

As long as all is good, you can add an extra handful or an additional 10 minutes of grazing each day and increase the amount from there. As long as the grass is introduced gradually, your guinea pig can have several handfuls daily or graze for a few hours a day without an issue.

Rich spring grass is delicious for guinea pigs but it can cause stomach upset if fed too much!

Can Guinea Pigs Eat Too Much Grass?

Guinea pigs are pretty good at self-regulating when they are eating grass. With that said, guinea pigs can eat too much grass on occasion. For example, if your guinea pig is not used to eating grass or if they’ve been off of it for the winter, it can cause some digestive upset or diarrhea if it’s fed too much at once.

Also, the new growth of grass in the spring is richer and more likely to cause these issues if it’s given in large quantities without a gradual introduction.

As long as the grass is introduced slowly, guinea pigs can generally eat grass in unlimited amounts and they will stop or slow their eating when they are full.

However, it’s always a good idea to observe your own guinea pig. If they seem a bit sick or lethargic after eating grass, or if their stools become soft, you may need to slow their intake of grass and introduce it more slowly until their body adapts.

Can Guinea Pigs Eat Grass Instead of Hay?

Hay is generally recommended to make up 80% of your guinea pig’s diet. However, since hay is essentially just fresh grass that has been dried and cured, they contain most of the same nutrients and fiber content. This means that grass can replace some of your guinea pig’s hay requirements.

TJ, the king of the hay bale.

However, it’s still a good idea to include some dried forage in their diet as well. Fresh grass is softer and may not wear down your guinea pig’s back molars as well as hay over time. This can lead to potential dental issues like malocclusion.

Fresh grass is also more likely to cause soft stools, while hay usually prevents this. Feeding both fresh grass and hay gives you the benefits of both and provides a nice balance for your piggies.

Also, if you’re feeding your guinea pig grass regularly, make sure it is not a grain or legume-based type of grass. The most common type of legume grass is alfalfa, which is safe in small quantities but contains too much calcium to feed in large amounts.

Grain-based grasses like barley, oat, wheatgrass, or ryegrass are safe for guinea pigs, but they can cause excess weight gain if they are fed frequently over time.

Can Guinea Pigs Eat Mowed Grass Clippings?

Guinea pigs should never eat mowed grass clippings. There are a few reasons for this. First of all, grass clippings ferment and rot much faster than fresh grass.

When grass clippings ferment in your guinea pig’s stomach, this can cause severe gastrointestinal issues such as bloat and GI stasis. These issues can be dangerous and even life-threatening to guinea pigs.

In addition, lawnmower clippings are mixed with fuel which is toxic to guinea pigs. Grass clippings can also be mixed with poisonous weeds or leaves as they go through the mower, which your guinea pig should not ingest.

To safely feed your guinea pig grass, be sure to pick fresh grass by hand or with scissors only, and rake up any mowed grass clippings before letting your guinea pig graze outside.

Can Guinea Pigs Eat Wet Grass?

It’s best to avoid feeding your guinea pig wet grass. This is because wet grass is a perfect breeding ground for mold and bacteria. If you go through extended periods of dampness, this increases the chances even more. Wet grass also has a tendency to rot and ferment faster once picked. Eating wet grass is also more likely to cause soft stools for your guinea pig.

Additionally, if you take your guinea pig out to graze, the wet grass will get their bellies and legs quite damp which can lead to skin infections or cause them to catch a chill and get sick. Guinea pigs are very low to the ground, so they can get cold very quickly being in contact with wet grass. If you pick grass for your guinea pig, it’s generally best to avoid collecting grass first thing in the morning when it’s covered in dew and mist from overnight.

Can Guinea Pigs Eat Wheatgrass?

Wheatgrass is a popular health food and it’s also super easy to grow yourself. You can often find wheatgrass in health food stores or as seeds or kits to grow your own.

Wheatgrass is very popular for guinea pigs too, and they love it! Since wheatgrass is a grain-based grass, it can cause guinea pigs to gain weight at a faster rate than regular grasses. For this reason, it shouldn’t be fed in large amounts as a replacement for their normal hay and forage.

However, it is perfectly safe to feed wheatgrass to your guinea pigs in moderation a few times a week. You can grow a few pots on your windowsill and let your piggies nibble away at it as it grows.

Can Guinea Pigs Eat Cat Grass?

Cat grass is typically made up of a combination of grain-based grasses like wheatgrass, barley, oat, and ryegrass. Grain-based grasses can cause excess weight gain if they are a regular part of the diet, but they are safe to feed in moderation a few times a week.

This means that cat grass is safe for guinea pigs as long as you don’t go overboard. The majority of the forage in your guinea pig’s diet should be non-grain grasses like timothy, orchard, bluegrass, brome, or sweet meadow grass.

Can Guinea Pigs Eat All Types of Grass From Outside?

Guinea pigs can eat any type of regular, untreated grass from your yard. However, some types of grass are better for guinea pigs than others.

Guinea pigs thrive on timothy and orchard hay, so growing timothy or orchard grass gives them some variety in both fresh and dried form while maintaining the same level of nutrients. You can often find small packs of timothy and orchard grass seeds on Etsy.

However, other types of grass that your guinea pig can eat include brome grass, bluegrass, Bermuda grass, buffalo, or sweet meadow grass.

Grain-based grasses are also safe for guinea pigs but they are higher in fat and shouldn’t be fed in unlimited quantities. Some of these include barley, oat, wheatgrass, and ryegrass. Cat grass fits into this category as well since it is usually made up of a combination of grain grasses.

Guinea pigs can eat many varieties of grass found outside, but some types are better than others!

These types of grain-based grasses can be grown for guinea pigs and fed a few times a week, but they should not be a replacement for your guinea pig’s main forage.

Legume grass, most notably alfalfa, is best avoided or fed in small quantities to guinea pigs as it’s higher in calcium than other grasses. Young or pregnant guinea pigs can eat alfalfa hay or grass on occasion, but adults over 6 months old shouldn’t eat it regularly.

Benefits of Feeding Your Guinea Pig Grass

Grass is a natural part of your guinea pig’s diet and can benefit your furry potato’s health in several ways, which I’ll cover below.

1. Grass is a Natural Part of Your Guinea Pig’s Diet

As grazing herbivores, grass is a very natural source of forage for your guinea pig. Grass and weeds more closely resemble their ancestors’ natural diets, making it a great thing to include in your domesticated piggy’s diet.

Grass and hay should make up 80% of your guinea pig’s diet, so mixing it up between fresh and dried forage gives them more variety and resembles their natural diet more accurately.

2. Grass is High in Fiber and Low in Sugar

Like hay, grass is fiber-rich and easy for guinea pigs to digest. It is also low in sugar and calcium, making it a suitable type of food for guinea pigs to munch on throughout the day.

Guinea pigs need to be constantly eating to keep their digestive tract running smoothly and prevent GI stasis and other gut issues. Since grass is low in sugar and high in fiber, it is suitable for guinea pigs to eat frequently without concern for excess weight gain or gut issues.

3. Eating Grass Helps Wear Down Your Guinea Pig’s Teeth

One of the main benefits of hay is its ability to wear down your guinea pig’s teeth over time due to the repeated chewing motions required to eat the long and fibrous strands. Eating several strands of grass usually has the same effect.

The back molars especially need to be filed down, and these require long strands of grass or hay to reach them. Since your guinea pig’s teeth are constantly growing, they need to constantly be eating forage to wear them down.

Chew toys are great, but they typically only reach the front teeth. The back molars far down in your guinea pig’s mouth are the most important to wear down, as these can grow inwards and trap the tongue if they are not kept short.

Pretty Daisy grazing outside.

4. Guinea Pigs Often Like Grass More Than Hay

In addition to everything else, guinea pigs also LOVE fresh grass. Most piggies wheek excitedly for a fresh pile of grass in their cage and you will rarely find a guinea pig that turns up their nose at it.

This can make fresh grass a great option for guinea pigs that don’t eat enough hay. Grass is often more enticing to them and it has many of the same nutrients and benefits that you’ll find in regular hay.

Risks of Feeding Your Guinea Pig Grass

While grass makes a great addition to your guinea pig’s diet, there are a few potential drawbacks to feeding it, which I’ll cover below.

1. Grass From Outside Can Contain Bugs or Parasites

As with anything outdoors, grass can contain parasite eggs, bugs, or similar things. There is always a risk of this, but you can reduce this somewhat by thoroughly rinsing the grass with clean, cool water right before giving it to your guinea pig. Be sure to pat the grass dry before feeding as many guinea pigs will avoid soggy grass.

If you take your guinea pig outside to graze, there is also a risk of small bugs getting into their fur. Since piggies are low to the ground and not generally fast moving, this makes it likely that they will come into contact with things in nature. However, most bugs are pretty harmless and will jump or fall off again.

Generally, the pros of taking your guinea pigs outdoors outweigh the cons.

2. Too Much Grass Can Cause Digestive Upsets

If you feed too much grass too quickly, there is a chance it can upset your guinea pig’s stomach. Even though grass is good for them, it’s important to increase the amount gradually to prevent any digestive upsets.

Early spring grass may be more likely to cause these issues as it is richer than grass that grows later in the year, so be sure to introduce it slowly.

3. Some Weeds and Plants Growing With Grass Can Be Poisonous

Some types of weeds and plants are toxic to guinea pigs, and these can sometimes be found growing alongside the grass outside. Some types of fallen leaves from trees may also be poisonous. If you’re unsure, it’s a good idea to research the plants growing nearby and rake up the area before letting your guinea pigs graze.

4. Pesticides and Chemicals Pose Health Risks to Guinea Pigs

Pesticides, herbicides, fertilizers, or any other chemicals are very toxic to guinea pigs and can lead to serious health consequences. It is absolutely crucial that you are positive an area is safe before picking grass for your guinea pig. Guinea pigs can also get sick from animal urine in the grass or from car exhaust residue, so it’s a good idea to avoid areas where cars and other animals frequent.

5. Grass Clippings From Lawnmower Can Be Dangerous

Additionally, it’s important to never feed your guinea pig any mowed grass cuttings from the lawnmower. Grass from the lawnmower can ferment quickly in your guinea pig’s stomach, causing bloat, which can be deadly.

Mowed grass can also be mixed in with toxic weeds or leaves that your guinea pig shouldn’t eat. If your lawn has been freshly mowed, be sure to rake up any grass clippings before taking your guinea pig out to graze.

It’s important to rake up grass clippings or toxic leaves before letting your guinea pig graze.

6. Weather Related Health Effects

Guinea pigs do not sweat, so they are at an increased risk of getting heat stroke in the hot weather. Additionally, they can also get chilled and catch an infection if the weather is too cool.

For these reasons, it’s best to only take your guinea pig outside when the temperature is between 60-85 degrees Fahrenheit. If the temperature is not within this range, it’s better to wait until a different time of the day or pick the grass by hand instead to give them in the cage.

It’s generally best to avoid taking your piggies outside first thing in the morning, as the temperature is usually cooler and the grass may be wet with dewdrops from the previous night.

Growing Grass Indoors for Your Guinea Pig

If you live in an apartment or if your grass is treated with chemical solutions, you can still grow grass in pots and planters for your guinea pig. Grass grows well in windows, balconies, or on your front step.

All you’ll need to grow your own fresh grass is a planter and some basic soil. Grass is not too fussy about soil quality or other conditions. Simply water it regularly and place the pot in an area where it will have some sunlight to grow. Avoid using any fertilizers or overwatering as this can cause mold to grow.

Types of Grass to Grow For Your Guinea Pig

There are different types of grass you can grow for your guinea pig. Wheatgrass or cat grass seeds are easy to grow and safe for guinea pigs. You can also often find wheatgrass growing kits that have all the things you need to grow it.

Wheatgrass seeds are commonly available in stores like Walmart and garden centers in early spring, or you can find them online. It’s always best to choose organic seeds when available. However, as grain-based grasses, wheatgrass and cat grass can be a little more fattening for your guinea pig than regular grass.

You can also dig out a small plot of grass from outside and put it in a pot indoors to grow. You can grow some from regular grass seed too but try to find a basic natural grass seed without fertilizers or additives included.

If you want to be certain that you have a good type of grass for your guinea pig, you can purchase timothy or orchard grass seeds online, such as from Etsy. It’s easiest to find seeds in the early spring and buy enough to last the rest of the year, as they may not be as readily available all year round.

Herbs That Guinea Pigs Can Eat

As herbivores, guinea pigs were designed to consume forage like herbs and grasses on a regular basis. In addition to grass, here are some great herbs you may want to try out with your guinea pig:

Skylar devouring some fresh dandelion leaves from the yard.
  • Dill: This feathery green herb is strongly scented and vitamin-rich.
  • Mint Leaves: Guinea pigs can eat both spearmint and peppermint leaves, but not all piggies love their powerful aroma.
  • Cilantro: This herb is a favorite among guinea pigs, but it shouldn’t be fed to pregnant females as it slows blood clotting.
  • Parsley: While rich in vitamin C and beloved by most guinea pigs, parsley should be fed in moderation due to its calcium content.
  • Basil: This herb is popular and easy to grow, but it is high in calcium.
  • Thyme: This extremely nutrient-rich herb is also incredibly high in calcium, so feed it very sparingly.
  • Fennel: Safe to feed the bulb and greens, fennel is popular among guinea pigs and lower in calcium than most other herbs.

For an even more detailed list of the herbs that guinea pigs can eat, be sure to check out our complete list of safe herbs for guinea pigs. Keep in mind that most herbs are very high in calcium and should be fed sparingly to prevent bladder stones in your guinea pig. It’s important to feed herbs along with several low-calcium foods to balance out the ratio of calcium in their diet.

More Foods That Guinea Pigs Can Eat

Did you know that guinea pigs can also eat asparagus, kohlrabi, and corn on the cob?

These foods all contain various nutrients that can boost your guinea pig’s health in numerous ways. They can also eat watermelonbananas, pears, and so much more.

For a complete list of all the fruits and vegetables that guinea pigs can eat, check out our article, Complete List of Safe Foods for Guinea Pigs.

Peach and Daisy playing tug of war with some dill.

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