MOHRSThe Importance of Hay in Maintaining Good Dental Health
As with most animals (and humans), teeth are used to break down food at the very beginning of the digestive cycle. For a rabbit, teeth play an even more important roll: teeth are the gateway to good digestive health – provided the rabbit has access to a proper diet.
Understanding The Dental Anatomy Of A Rabbit
Rabbits have four large front teeth, called incisors, which can easily be seen by gently lifting the lips of a bunny. Behind the upper incisors are two smaller teeth called peg teeth, which are not as easily seen. Further back in the mouth are the premolars and molars, often referred to as “cheek teeth.” The cheek teeth are separated from the incisors by a fairly long open space called a diastema. Six upper and five lower cheek teeth can be found on each side of the mouth, making for a total of 28 teeth. The incisors function similar to scissors and are used to grasp, slice, tear, and cut through vegetation. Cheek teeth grind and chomp food into smaller pieces so they can be swallowed.
When at rest, the tips of the lower incisors are normally positioned between the upper incisors and the peg teeth. The cheek teeth, however, should be slightly out of alignment in the “at rest” position. The cheek teeth are brought into alignment (occlusion) when the jaw (mandible) is slightly retracted and angled so that the jaw joint (temporomandibular joint) can reposition itself, allowing the cheek teeth to come together while at the same time separating the incisors. This allows the cheek teeth to move laterally while chewing without interference from the incisors. The tongue, of course, plays an important role by moving food from the incisors back to the cheek teeth where it is ground.
All their teeth continue to grow throughout the rabbit’s life. This means rabbits need to continually chew and grind food to keep the teeth worn so they can function properly. According to Dr. David Crossley of the Animal Medical Centre Referral Services in Chorlton, Manchester, UK, “Three to four millimeters of incisor tooth are worn away each week, with the cheek teeth wearing around this amount every month.”** Because a rabbit’s teeth are made to wear down rapidly, an improper diet can affect the teeth in just a few days. Therefore, the type and form of food a rabbit eats is extremely important for maintaining healthy tooth wear. Grass hay (such as Timothy hay and orchard grass) and other leafy vegetation are very abrasive and full of many different mineral particles. It takes a rabbit more time and requires more effort to eat grass and hay than it does to eat commercial pellets. Grass hay must be sliced into short sections by the incisors, and then ground by the cheek teeth, which move laterally; therefore, grass hay helps to wearthe teeth down. Pelleted foods on the other hand, are quickly crushed by the cheek teeth; grinding and lateral chewing motion is significantly reduced, which results in only partial tooth wear and the potential for the development of painful spurs.
A diet comprised mostly of grass hay will cause more tooth wear than a diet in which pellets are the main source of food.
It is also important to note that the lower teeth (mandible teeth) grow up to 11⁄2 times faster than the upper (maxillary) teeth, and, as noted previously, there are more upper teeth than lower teeth. Because of these differences, Dr. Crossley points out that “abnormalities of a tooth in one jaw may affect up to three teeth in the opposite jaw.” To help prevent these teeth problems, Dr. Crossley recommends rabbits spend several hours a day chewing grass hay and leafy vegetation. When a rabbit spends more time chewing hay, more saliva is produced, as well, which also aids in digestion.
Hay Is The Single Most Important Factor In Maintaining Rabbit Teeth
Pellets do contain fiber, but the fiber is in very short pieces that require little grinding. Most rabbits who are fed a diet of pellets only will not be able to properly wear down their teeth. When that happens, sharp edges or points (called spurs) will develop on the sides of the cheek teeth. Some of these spurs can become long enough to cut the tongue and/or the inside of the cheeks, which is very painful. This can lead to soft-tissue abscesses; cause drooling, extreme pain, and difficulty in closing the mouth; and may cause the rabbit to stop eating and drinking. Also, teeth that don’t meet up properly (misalignment of the teeth, or malocclusion) can cause tooth roots to become elongated, impacted, and inflamed. This can eventually lead to an inflammation in the jawbone and can cause an extremely painful abscess to form. Elongated roots on the upper jaw of a rabbit can even affect the eyes, which may result in “runny” eyes, bulging eyes, and inflammation, which can cause a retrobulbar abscess (an abscess behind the eye). If untreated by a rabbit-savvy veterinarian, this can lead to death.
As with any potential health issue, preventive measures are the best course of action. Just as with humans, a rabbit’s teeth need to properly align when the jaw is closed. Some causes for a malocclusion are trauma to the teeth, genetics, and a diet that is low in fiber. Incisors that are maloccluded can curl outward, curl inward, or even grow into the upper palate of a rabbit’s mouth. They can also prevent the rabbit from being able to eat or drink anything. These teeth need to be trimmed, and, in some cases, completely removed by a good rabbit veterinarian.
While some dental problems cannot be solved by a proper diet alone, it is safe to say that providing your rabbit with continual access to quality grass hay will go a long way toward good health.
Tips To Get Your Rabbit To Eat More Hay
• Limit the amount of pellets you feed your rabbit so he is encouraged to eat more hay.
• Feed only the best quality grass hay; much of the hay that is sold in pet stores is brown, dusty, not fresh, and therefore not palatable for your rabbit.
• Have hay available where your rabbit can reach it easily such as close to a favorite resting spot and in one side of the litter box. Many rabbits like to nibble hay on one end and use the other end for defecation and urination.
• Stuff hay into their favorite toys (wire balls, the cardboard roll left from a used roll of toilet paper) or place a mound of hay blocking a favorite tunnel so your bunny has to forage and move it (and hopefully eat it) to go through the tunnel.
• Mix hay in with foods your bunny likes, such as herbs or vegetables; a rabbit who is reluctant to eat hay may end up accidentally “tasting” it and realize it is pretty good.
Things To Watch for in Dental Health
• Watch for changes in the eating habits of your rabbit: no longer eating produce (veggies) or biting off small pieces with the incisors but not eating them (may indicate molar spurs), ignoring pellets or having a hard time chewing them, eating less hay than usual, small fecals.
• Gently feel around your rabbit’s head and jaw and around the eyes; look for bumps or lumps that are on one side but not the other.
• Watch for runny eyes, sneezing, and lumps on the lower jaw.
• Gently lift the upper lips to inspect the incisors for proper occlusion (meeting evenly).
• Watch for drooling.
• Sniff around your bunny’s mouth; sour or rotten breath can be an indication
of a tooth problem and should be checked out by your rabbit veterinarian immediately.
• Runny eyes (ocular discharge) may indicate a tooth root that is blocking a nasolacrimal duct.
• Some dwarf breeds and some lop rabbits are more prone to dental problems because of the shape of their head and inbreeding.
• Once dental problems begin to affect how efficient the teeth can chew, most rabbits will change their eating habits. Some rabbits will show more interest in eating higher energy foods such as pellets instead of hay and other leafy vegetation. If this happens, and the problem is not corrected immediately by your rabbit veterinarian, it can lead to serious medical consequences that can be difficult if not impossible to reverse.
Key Points To Remember
• Know your rabbit’s eating habits, and if changes occur, see your veterinarian immediately.
• Structure your rabbit’s diet to minimize dental problems and maximize their health: 80% of their diet should be grass hay.
• Be sure to have your rabbit veterinarian check your rabbit’s teeth periodically, even if there are no obvious problems.
• Remember: A diet that promotes healthy chewing for several hours a day means that not only will your rabbit be less likely to develop a malocclusion or other dental problems, it should also help satisfy his natural desire to chew (and possibly save your furniture from destruction).