Rabbits, often simply called bunnies, are classified as obligate herbivores. This designation means their entire physiology, from their teeth to their digestive tract, has evolved to thrive exclusively on a plant-based diet. An obligate herbivore cannot survive long-term without the specific nutrients and structural components found in plants, particularly high fiber content. This strict dietary requirement is fundamental to their health and survival.
The Rabbit’s Required Diet
The nutritional foundation of a healthy rabbit’s diet must be a high intake of coarse fiber. This fiber, primarily derived from grass hay, is the most important component for gastrointestinal and dental health. Adult rabbits should have an unlimited supply of high-quality grass hay, such as Timothy, orchard, or oat hay, constituting approximately 80 to 85 percent of their daily food intake.
This continuous consumption of hay provides the long-strand fiber necessary to stimulate gut motility, ensuring the digestive system keeps moving properly. Fresh, leafy green vegetables should supplement the hay, offering additional fiber, moisture, and micronutrients. Greens, such as romaine lettuce, dandelion greens, or cilantro, should make up about 10 to 15 percent of the diet.
Commercial pellets are only a minor, supplemental part of the diet, typically comprising less than five percent. Pellets offer concentrated vitamins and minerals but are energy-dense and lack the long-strand fiber found in hay. Overfeeding pellets can lead to obesity and metabolic issues, making hay the primary dietary component.
Specialized Digestive Process
The necessity of a high-fiber diet is rooted in the rabbit’s specialized digestive process, known as hindgut fermentation. Unlike ruminants like cows, rabbits are monogastric, meaning they have a simple stomach. They possess a large pouch called the cecum, which acts as a fermentation vat. This cecum houses beneficial microorganisms that break down plant cellulose that the rabbit’s own enzymes cannot digest.
The rabbit’s large intestine efficiently separates ingested fiber into two types. Large, indigestible fiber particles stimulate gut movement and are rapidly excreted as hard, round fecal pellets. Conversely, small, digestible fiber particles are shunted back to the cecum for microbial fermentation.
This fermentation process yields nutrients, including volatile fatty acids for energy, B vitamins, and protein. These nutrients are packaged into soft fecal pellets called cecotropes, which the rabbit re-ingests directly from the anus. Cecotrophy is a biological mechanism for absorbing these nutrients created in the cecum, completing a highly efficient digestive cycle.
Dental Adaptation for Herbivory
A rabbit’s ability to process tough plant matter is facilitated by a unique dental structure adapted for continuous grinding. Rabbits possess aradicular hypsodont teeth, meaning their incisors and cheek teeth (molars and premolars) grow continuously throughout their entire life. This constant growth is necessary because the abrasive nature of their high-fiber diet causes significant wear on the tooth surface.
The constant chewing motion, specifically the lateral (side-to-side) grinding of hay, is required to wear down the molars evenly. If the diet lacks sufficient abrasive fiber, the teeth do not wear properly, leading to a condition called malocclusion. This misalignment causes sharp projections, or “spurs,” to develop on the teeth, which can injure the rabbit’s tongue and cheek tissue. The act of chewing hay thus serves a dual purpose: it stimulates the digestive system and maintains the equilibrium between tooth growth and wear.