Feeding Rabbits Right
pet age 1 JULY 2005
BY DR. PETER G. FISHER
Rabbits have an unparalleled ability to utilize low-grain, high-roughage
diets to produce body protein and meet their knutritional needs. To understand
the potential complexities involved in properly feeding rabbits, however^ you
must first develop an understanding of their unusual digestive tracts.
How Rabbits Process Fiber
Rabbits are hind-gut fermentors. That means they digest much
of their food in the cecum and colon, which are at the end of the digestive
tract. The cecum acts as a huge fermentation chamber where microflora (bacteria
and protozoa) aid in digestion. Fiber helps these beneficial bacteria and protozoa
stay in balance and function properly.
Not all the fiber ingested is fermented, however. Instead, indigestible fiber
is sorted out and expelled from the body when digesta enters the rabbit's large
intestine. There, muscular contractions help separate the fiber and nonfiber
fractions and simultaneously send them in opposite directions.
The high-fiber component moves to the colon and is voided from the body as daytime
or hard feces—the normal stool most people associate with rabbits. The
nonfiber fraction moves to the cecum where fermentation by the
bacteria and protozoa produces amino acids, nitrogen and urea, all of which
the rabbit uses to make protein. The cecal microflora also produce water-soluble
vitamins and volatile fatty acids, a major source of energy for the hind gut.
Some nutrients produced as a result of this fermentation process are absorbed
across the cecal wall into circulation for use in body functions. The remaining
contents form pellets, called cecotropes, that are abundant in vitamins and
amino acids. They are voided from the body approximately eight hours after the
rabbit eats. Rabbits consume these nighttime or soft feces directly from the
anus. This practice is a source of energy and vitamins for the rabbit, and is
influenced by dietary protein and energy. When fed a high-fiber, low-protein
diet, cecotrope ingestion is maximized.
Fiber also is needed to stimulate motility of the gastrointestinal tract, allowing
ingested food to move properly so normal digestion can take place. Without fiber,
the gastrointestinal tract slows down, which may result in subsequent changes
in the cecum pH, fermentation and bacterial populations. Over time, these changes
may result in indigestion or gastrointestinal stasis.
A rabbit with GI stasis will be anorexic or have a reduced appetite. An affected
rabbit produces very small stools or none at all, and may be hunched
up or grind its teeth in response to painful gastrointestinal gas formation.
Diarrhea with mucous may or may not be present.
How Hays Differ
Since hay is the primary source of fiber in a rabbit's diet,
it should be fed to them on a free-choice basis. In other words, make sure plenty
of fresh, good-quality hay is always available. A minimum dietary fiber of 20
percent to 25 percent is required.
The primary types of hay include grass hay (timothy, oat, brome, orchard) and
legume hay (alfalfa, clover, pea and peanut). Many factors affect the nutritional
value and quality of hay—soil, weather conditions during growth and harvest,
and the stage of maturity when the hay is harvested. These factors will affect
the appearance and palatability of the hay as well as how long it can be stored
in good condition.
As a general rule, grass hay (timothy) is recommended over legume hay (alfalfa)
for the average adult pet rabbit. The primary reasons are that tim-pthy hay
is lower in protein and calcium and higher in fiber than alfalfa hay. The higher
fiber helps keep the rabbit's digestive system in balance, and the low.er protein
content encourages the ingestion of nutrient-rich .cecotropes.
Hay prevents boredom by satisfying the rabbit's innate desire to chew, and at
the same time helps maintain dental health. Rabbits' teeth continue to grow
throughout most of their lives, and can grow up to 5 inches per year. Feeding
grass hay on a free-choice basis promotes constant chewing, which helps wear
down the continuously growing molars and prevents overgrowth of painful molar
spurs or points. Rabbits with molar spurs will have depressed appetites, and
may be observed dropping food from their mouths as they attempt to chew.
How Diet Affects Calcium Levels
Rabbits are unique in that they absorb nearly all dietary calcium
from the intestines, and excrete excess calcium in the urine. Blood calcium
levels fluctuate in proportion to dietary intake, and the excretion of calcium
increases in parallel with the amount of calcium ingested.
Rabbits on high-calcium diets will produce the same volume of urine, but with
higher concentrations of calcium.
The high levels of urinary calcium may precipitate into insoluble crystalline
salts, resulting in cloudy urine. High concentrations of calcium in the urine
also may result in thick aggregations of calcium crystals called sludge, which
inhibit normal bladder function. Excess urine calcium also may form concretions,
recognized as uroliths or bladder stones.
To decrease the likelihood of these problems, feed lower-calcium grass hays
such as timothy to adult rabbits. In addition, look for pelleted diets with
a calcium content in the range of 0.5 percent to 1 percent (the higher end of
this range for pregnant and lac-tating rabbits), with a calcium to phosphorus
ratio in the range of 1.2-2 to 1.
It's OK to feed alfalfa hay to young bunnies (under the age of 6 months) because
it provides extra calcium necessary for growing bones and extra protein for
developing muscles. However, offer timothy hay at the same time. That way, it
will be easier to wean them to a diet with only grass hay.
It's OK to feed alfalfa to rescue bunnies that are thin and weak, and to bunnies
recovering from major surgery or severe illness. Additionally, you many entice
"senior" bunnies with reduced appetites to eat fiber by offering alfalfa.
Alfalfa tends to be very appealing to rabbits and will promote weight gain and
give a nice luster to their fur.
SWITCHING RABBITS TO NEW PELLETS
When converting rabbits from one brand of pellet to another, do so gradually to help prevent digestive upset. The "five-I fifths" rule is a good method to follow. If a rabbit eats one-fourth cup of pellets per day, use this formula:
* Days 1through 5: 1cup of the old brand mixed with one-fourth
cup of the new brand, I divided into five servings (one serving per day).
* Days 6 through 10: Three-fourths cup of the old brand mixed with one-half
cup of the new brand, divided into five servings (one serving per day).
* Days 11 through 15: One-half cup of the old brand mixed with three-fourth
cup of the new brand, divided into five servings (one serving per day).
* Days 16 through 20: One- fourth cup of the old brand mixed with 1cup of the
new brand, divided into five servings (one serving per day).
* By day 21, the rabbit should be switched over to its new feed.