Rabbits are herbivores, and their diet consists almost entirely of grass and hay. This plant material is the single most important component of their daily intake. For a healthy adult rabbit, grass hay should constitute approximately 80 to 85% of their total diet, providing the necessary fiber. High-fiber consumption is essential for maintaining the continuous function of both their teeth and their gastrointestinal system.
Essential Grasses and Hays for Rabbits
The foundation of a healthy adult rabbit’s diet is grass hay, with Timothy hay being the most widely recommended choice due to its balanced nutritional profile. Timothy hay is high in fiber, moderate in protein, and low in calcium, making it suitable for long-term daily feeding. The texture of Timothy hay is categorized by its cut, which influences its coarseness and nutritional content.
The first cut, harvested earliest, has thicker stems and is highest in fiber, making it excellent for dental wear and weight maintenance. The second cut is the most common variety, offering a good balance of fiber and leafier material. The third cut is the softest and leafiest, containing slightly lower fiber but being highly palatable for older rabbits or those transitioning diets.
Several other grass hays offer suitable alternatives or additions to Timothy hay, providing variety in texture and flavor. Acceptable grass-based options that can be included in a rotational mix include:
- Orchard grass hay, known for its soft texture and sweet smell.
- Meadow hay.
- Brome grass.
- Oat hay.
Legume hays, such as Alfalfa and Clover, are distinctly different from grass hays and should be limited for most adult rabbits. These hays are significantly higher in calories, protein, and calcium, which can lead to obesity and urinary issues, such as bladder sludge. Alfalfa hay is appropriately fed only to young, growing rabbits under seven months old, or pregnant or nursing does, as they require the extra nutrient density.
The Role of Grass in Dental and Digestive Health
The constant chewing of abrasive grass fiber is necessary because rabbits are hypsodonts. This means their teeth, including incisors and cheek teeth, grow continuously throughout their lives at a rate of roughly 2 millimeters per week. The side-to-side grinding action of the jaw during the chewing of coarse hay wears down the dental surfaces evenly.
A diet lacking sufficient abrasive fiber fails to provide this necessary wear, leading to overgrown teeth and the development of sharp enamel points, known as spurs, on the molars. These dental problems cause pain, difficulty eating, and eventually malocclusion, a misalignment that prevents proper chewing and can lead to secondary health issues. The long, indigestible fiber found in hay acts like a natural file, keeping the entire dental structure at a healthy length.
In the digestive system, long-strand fiber stimulates gut motility, the continuous muscular contractions known as peristalsis. This constant movement is required because rabbits cannot vomit, and their digestive tract must always be moving food through. When a rabbit consumes enough hay, the long fiber particles trigger the release of hormones that promote gut movement, preventing gastrointestinal stasis.
Fiber is also separated in the hindgut into digestible and indigestible components, a process that is influenced by particle size. The smaller, digestible fiber is fermented in the cecum, a large organ where beneficial bacteria produce nutrient-rich pellets called cecotropes. The quality of the fiber intake is directly related to the production of healthy cecotropes, which rabbits re-ingest to obtain essential vitamins and proteins.
Guidelines for Safe Grass and Hay Feeding
Grass hay should be provided to a rabbit in unlimited quantities, offered in multiple locations such as feeders and spread throughout the enclosure to encourage foraging. A healthy adult rabbit should consume a volume of hay roughly equivalent to their body size every day.
While fresh grass is more nutritious than hay, it must be introduced into the diet very slowly to avoid severe digestive upset. A sudden increase in moisture and nutrient content can disrupt the delicate balance of the gut flora, leading to diarrhea. Fresh grass should only be given to a rabbit once its digestive system has successfully adapted to a high-hay diet over time.
Never feed a rabbit grass clippings collected from a lawnmower. The crushing action of the mower blades causes the grass to ferment rapidly, which can lead to gas buildup and fatal bloat. Hay must also be stored in a cool, dry, and well-ventilated location to prevent the growth of mold and mildew, which can be highly toxic to rabbits.