# Can guinea pigs eat groundsel?

> Better left off the menu. Verdict: avoid. Never · None — do not feed · fresh and raw only.

Photo: A groundsel plant with small yellow flowers.

**Where sources disagree on this food:**

> "The plants most often implicated include ragwort ( S jacobea ), groundsel ( S riddellii , S longilobus ), rattleweed ( Crotalaria retusa ), and seeds of yellow tarweed ( A intermedia )." (Merck Veterinary Manual (Professional version), grade S)

> "PA levels in the plant materials were 3767, 2792 and 1674 µg g-1" (PubMed (Food Addit Contam Part A), grade A)

> "Toxicity of pyrrolizidine alkaloids from Riddell groundsel (Senecio riddellii) to cattle" (PubMed (Am J Vet Res), grade A)

> "Groundsel" (RVC Beaumont Sainsbury Animal Hospital, grade A) [minority position]

We still give one verdict — rank the higher-graded sources first and never average the positions. The full resolution is in the sources section below.

## Quick answer

No — and this page has an unusual job: overruling a source we otherwise trust. RVC's factsheet lists "Groundsel" among its safe Wild Garden Herbs/Weeds/Flowers. But Merck's veterinary manual names groundsel among the plants "most often implicated" in pyrrolizidine alkaloidosis — a chronic liver failure of cattle and horses — and common groundsel has been measured at about 2,800 µg of pyrrolizidine alkaloids per gram of dried plant (PMID 32870736).

With one safe listing against a toxicology register that strong, the no-averaging rule we operate under does not let us split the difference on a liver toxin. The RVC line is quoted verbatim in the sources section below — and then overruled. The shared explainer on this page covers what pyrrolizidine alkaloids do and why the guinea-pig resistance story doesn't rescue this plant.

## What the sources say about groundsel

What the sources say: beyond Merck's genus-level listing, the feeding-harm record is real, not theoretical — cattle-toxicity trials of groundsel species are on record (Riddell groundsel, PMID 2021243; threadleaf groundsel, PMID 6703456), and a 2024 horse case report extends the pattern. For guinea pigs specifically: nothing. No feeding study exists.

What's missing cuts both ways, so read it carefully. Laboratory work shows guinea pigs detoxify many PAs faster than livestock — and it also shows the resistance is alkaloid-specific, with jacobine unusually toxic to the species (PMID 8591728). Our recommendation: groundsel stays out of the cage, and this site owns that call.

## Pyrrolizidine alkaloids and guinea pigs

What the sources say. Pyrrolizidine alkaloid (PA) poisoning is a documented cause of chronic, cumulative liver failure in cattle and horses, caused by a range of plants "most commonly of the genera Senecio, Crotalaria, Heliotropium, Amsinckia, Echium, Cynoglossum, and Trichodesma" (Merck Veterinary Manual, PA toxicosis page, last updated September 2024). Each of the three plants on this register carries its own measured or trial evidence: groundsel among the most PA-rich plants ever quantified (PMID 32870736), comfrey roots and leaves inducing liver tumours in every rat feeding group (PMID 278864), and coltsfoot flowers doing the same in 8 of 12 rats (PMID 1269853).

What's missing. No feeding study of any of these three plants in guinea pigs exists — the searches are recorded on each page. Laboratory metabolism work shows guinea pigs detoxify most pyrrolizidine alkaloids faster than livestock species do (PMID 1907134; PMID 1440605), but that resistance is alkaloid-specific — jacobine, a major ragwort PA, is unusually toxic to guinea pigs (PMID 8591728) — and no safe feeding level has been established for any PA plant in this species. The 2020 systematic review of human case reports found that evidence unreliable (PMID 32105669); the animal trials stand.

Our recommendation: none of the pyrrolizidine-alkaloid plants — groundsel, comfrey or coltsfoot — belongs in a guinea pig's food, whatever a wild-herb safe list says. This site owns that call; the RVC listings are quoted verbatim in the sources section of each page rather than quietly dropped.

## What to do instead

Nothing to prepare — if groundsel is growing in the run or the hay patch, pull it before your guinea pig finds it. The plant is common in gardens, pastures and bare ground, and chickens and rabbits keepers face the same register; the whole plant carries the PAs.

Safe wild-herb picks exist on our register for keepers who forage: dandelion from unsprayed ground, or shop-bought herbs, cover the same slot without the PA register attached.

## Who stands behind this verdict

Written by [Patrick Li](/authors/patrick-li/). Editorially reviewed 2026-09-12 · Evidence checked 2026-09-12.

Evidence: Sources disagree · Extrapolated from another species · Sources reach different conclusions.

No veterinarian has reviewed this page. It is educational guidance checked by the author against the cited sources — for health decisions, talk to your vet.

## Wondering about these too?

| Food | Verdict | How often |
|---|---|---|
| [Avens](/guinea-pigs/can-guinea-pigs-eat-avens/) | safe | A few times a week |
| [Burnet](/guinea-pigs/can-guinea-pigs-eat-burnet/) | safe | A few times a week |
| [Calendula](/guinea-pigs/can-guinea-pigs-eat-calendula/) | safe | A few times a week |

**See also:** the [Food Checker](/guinea-pigs/what-can-guinea-pigs-eat/) photo wall covers every reviewed food with its verdict badge.

## Related tools

- [Guinea Pig Vitamin C Calculator](/guinea-pigs/vitamin-c-calculator/): Guinea pigs need 10–30 mg of vitamin C every day because they cannot make or store it. Converts the daily vitamin C target into food and supplement portions by life stage.

## Frequently asked questions

**Q: Can guinea pigs eat groundsel?**

We recommend no. RVC's wild-herb list is the only positive source; Merck's toxicology page, the measured PA content and the cattle trials all point the other way, and no guinea-pig feeding study exists to adjudicate.

**Q: Is groundsel the same as ragwort?**

They are close relatives in the same Senecio genus, and the toxicology register treats them together: Merck's PA page lists ragwort (Senecio jacobaea) first among the most-implicated plants, with groundsel species named alongside. Different plants, same mechanism, same verdict here.

**Q: Why does RVC list groundsel as safe if it is toxic?**

That is the honest conflict this page exists to show. RVC's factsheet is a feeding guide that lists groundsel among safe wild herbs; the toxicology register documents livestock harm. We quote the RVC listing verbatim, then follow the toxicology register — a single safe list line does not outweigh it for a PA plant.

**Q: What if my guinea pig ate groundsel?**

Remove the plant, note roughly how much and when, and call your vet for advice. PA harm is cumulative rather than sudden, but a one-off snack deserves a vet conversation — especially if wild plants are reachable in the run, because that is a fixable setup problem.

## Safety notes

Introduce any new food gradually: a small taste at first, building up over a week or so, and keep every serving fresh and raw. Hay stays the main event at around 80% of the day's eating, with fresh vegetables as the supplement.

**Warnings:**
- Merck's veterinary manual names groundsel among the plants "most often implicated" in pyrrolizidine alkaloidosis — a chronic liver failure of cattle and horses.
- Common groundsel has been measured at about 2,800 µg of pyrrolizidine alkaloids per gram of dried plant (PMID 32870736).
- RVC lists groundsel as a safe wild herb; this page keeps it off the menu anyway, and quotes the RVC listing in the sources section.

**When to contact your vet**: Guinea pigs hide illness well. Contact your vet promptly if your guinea pig stops eating or passes fewer droppings, seems lethargic or in pain, has diarrhea, or shows any sudden change in behavior — small pets go downhill fast, and same-day advice is always the safe call.

## The sources behind this verdict

1. [Merck Veterinary Manual (Professional version): Pyrrolizidine Alkaloidosis in Animals](https://www.merckvetmanual.com/toxicology/pyrrolizidine-alkaloidosis/pyrrolizidine-alkaloidosis-in-animals) (grade S, 2024-09). Scope: PA toxicosis overview: genera and species most often implicated. Excerpt: "The plants most often implicated include ragwort ( S jacobea ), groundsel ( S riddellii , S longilobus ), rattleweed ( Crotalaria retusa ), and seeds of yellow tarweed ( A intermedia )."
2. [PubMed (Food Addit Contam Part A): Transfer of pyrrolizidine alkaloids from ragwort, common groundsel and viper's bugloss to milk from dairy cows](https://pubmed.ncbi.nlm.nih.gov/32870736/) (grade A, 2020-11). Scope: Measured PA content of common groundsel (S. vulgaris) — the middle figure of the three plants. Excerpt: "PA levels in the plant materials were 3767, 2792 and 1674 µg g-1"
3. [PubMed (Am J Vet Res): Toxicity of pyrrolizidine alkaloids from Riddell groundsel (Senecio riddellii) to cattle](https://pubmed.ncbi.nlm.nih.gov/2021243/) (grade A, 1991-01). Scope: Feeding-toxicity evidence in cattle — the documented-harm species for this plant group. Excerpt: "Toxicity of pyrrolizidine alkaloids from Riddell groundsel (Senecio riddellii) to cattle"
4. [RVC Beaumont Sainsbury Animal Hospital: Feeding Your Guinea Pig (factsheet PDF)](https://www.rvc.ac.uk/Media/Default/Beaumont%20Sainsbury%20Animal%20Hospital/EXOTICS/Animal%20Care%20Factsheets/Guinea-pig-feeding-guidelines-and-advice-Dec-2022-NS.pdf) (grade A, 2022-12). Scope: Wild Garden Herbs/Weeds/Flowers safe list — the single positive listing, quoted verbatim and overruled. Excerpt: "Groundsel"
5. [Washington State Noxious Weed Control Board: Common Groundsel](https://www.nwcb.wa.gov/weeds/common-groundsel) (grade C, undated). Scope: Species-level side mention only (C-grade, cannot support the verdict alone). Excerpt: "It contains pyrrolizidine alkaloids, which can cause irreversible liver damage and possibly death."

### Where sources disagree

> "The plants most often implicated include ragwort ( S jacobea ), groundsel ( S riddellii , S longilobus ), rattleweed ( Crotalaria retusa ), and seeds of yellow tarweed ( A intermedia )." (Merck Veterinary Manual (Professional version), grade S)

> "PA levels in the plant materials were 3767, 2792 and 1674 µg g-1" (PubMed (Food Addit Contam Part A), grade A)

> "Toxicity of pyrrolizidine alkaloids from Riddell groundsel (Senecio riddellii) to cattle" (PubMed (Am J Vet Res), grade A)

> "Groundsel" (RVC Beaumont Sainsbury Animal Hospital, grade A) [minority position]


How we resolved it: RVC (A) lists groundsel on its safe wild-herb list, but it stands alone against the toxicology register: Merck (S) names groundsel among the plants most often implicated in PA liver failure, the measured PA content of S. vulgaris is among the highest ever quantified (PMID 32870736), and controlled cattle-toxicity trials exist for groundsel species. No guinea-pig feeding study exists on either side; the guinea-pig metabolic-resistance literature is real but alkaloid-specific — jacobine is unusually toxic to guinea pigs (PMID 8591728) — and no safe feeding level is established. Under the no-averaging rule the RVC line is quoted verbatim as the minority position and the verdict follows the toxicology register: avoid.

Grades rate the source, not the claim: S veterinary manuals · A research & university clinics · B welfare organizations · C practitioner education · D not cited. Methodology: /methodology/.

Written by Patrick Li. This guide is informational and not a substitute for veterinary care.
Canonical page: https://petguidecalc.com/guinea-pigs/can-guinea-pigs-eat-groundsel/