Understanding Hay Quality for Your Guinea Pigs and Rabbits

Understanding Hay Quality for Your Guinea Pigs & Rabbits

For guinea pigs and rabbits, hay isn’t just a snack—it’s their number one essential food. In fact, around 80–90% of their daily diet should consist of hay. This high-fibre food keeps their digestive system on track and supports healthy tooth wear, since both species have continuously growing teeth.

As a qualified veterinary nurse, I’ve learned that understanding hay quality is key to selecting the right nutrition, texture, and freshness for your pets.

Common Hay Types in Australia

Australia produces a wide variety of hay suitable for guinea pigs and rabbits. Each type has distinct nutritional profiles and life-stage suitability.

Timothy Hay (grass hay) – High fibre, moderate protein, low calcium; ideal for adult guinea pigs & rabbits.
Oaten (Oat) Hay – Moderate to high fibre, moderate protein; good for adults who appreciate seed heads and softer texture.
Lucerne (Alfalfa) Hay – High protein and calcium; best reserved for young, growing, pregnant or nursing animals.
Rhodes Grass Hay – Moderate fibre & protein; coarse, long strands help maintain dental and digestive health in adults.
Teff Hay – Fine grass hay, moderate fibre/protein; suits picky eaters or adults who prefer softness.

(Values based on CSIRO feed tables and Vetafarm small herbivore data.)

Nutritional Balance of Hay

Research by CSIRO shows that fibre should dominate the diet for hindgut-fermenters like guinea pigs and rabbits. High-fibre diets keep gut motility steady, support healthy microbial flora, and maintain good dental health. Legume hays like Lucerne are rich in nutrients but can upset this balance if used as the main hay for adults — they’re best used as supplements.

Harvest timing matters too: earlier-cut hay tends to be softer and greener (higher protein), while later-cut hay is coarser with higher fibre content. Both have their place depending on pet age and health.

Harvesting, Drying & Colour - which hay is best?

When hay is cut, dried and stored, its colour, aroma and texture can vary. Green hay often signals good drying and chlorophyll retention, but naturally yellow hay can still be high quality. What matters most is aroma and texture — it should smell fresh and grassy, feel soft to the touch, and not be brittle or musty.

Imported Hay & the risk of Gamma Irradiation

Some imported hays are gamma‐irradiated as part of Australia’s biosecurity process. This ensures pests or seeds don’t make their way in. Although irradiation (25–50 kGy) can slightly affect vitamins A/E or lipids, it does not reduce fibre quality or overall nutritional value (research by ANSTO & FSANZ). Many owners find imported hay such as premium Timothy offers consistency and high quality, especially when locally grown supplies vary.

At Guinea Pigs Australia, we offer both locally grown Australian hay and trusted imported options — giving you choice and flexibility based on your pets’ preferences and budget.

How to store your hay - Storage & Airflow

Proper storage ensures hay retains its quality.

Airflow matters: store in ventilated bags, boxes, or racks so hay can “breathe”.
Avoid sealed plastic: airtight plastic can trap moisture and lead to mould.
Don’t store it on the ground: to prevent condensation and moisture uptake, keep hay off flooring surfaces.
Store in a cool, dry environment: Target 15–25 °C with low humidity.
Regular checks: Good hay should feel soft, springy and smell sweet and grassy.

How to choose the right hay for your Guinea Pig or Rabbit

Fibre first: Hay should make up 80–90% of your guinea pig or rabbit’s diet.
Choose based on life stage: Grass hays (Timothy, Oaten, Rhodes, Teff) suit adults; Lucerne is best for young or nursing animals.
Freshness over colour: Smell, texture and softness matter more than just the shade of green.
Storage counts: Keep hay dry, ventilated, and away from sealed plastic and humidity.
Choice is good: Whether locally grown or imported, both types of hay can be excellent when selected and stored properly.

Blog References:

CSIRO Animal Nutrition – Forage & Fibre Requirements for Small Herbivores.

Vetafarm (Australia): “Why High Quality Hay is a Must-Have for Rabbits and Guinea Pigs.”

FSANZ: “Food Irradiation and Nutrient Stability.”

ANSTO: Gamma Irradiation Review for Agricultural and Animal Feeds.

Rothacher J. et al. (2023): A Comparison of Commercially Available Feeds for Rabbits & Guinea Pigs.

Department of Agriculture, Fisheries & Forestry (DAFF): Gamma Irradiation Biosecurity Standards.