Rabbits, herbivores, need a plant-based diet of hay, bunny pellets and healthy vegetables. The well-balanced diet provides an adequate supply of vitamin D, which rabbits need to properly absorb calcium and phosphorus from their food. Without enough vitamin D, rabbits can develop health problems -- but too much of this essential vitamin can poison them.
Vitamin D: The Necessary Vitamin
Vitamin D is a fat-soluble compound that comes in the form of ergocalciferol, or vitamin D2, and cholecalciferol, also known as vitamin D3. Plant sources provide vitamin D2; sunlight produces vitamin D3 in rabbits' bodies. Most types of rabbit feed contain some form of vitamin D to ensure captive rabbits get enough of it in their diets, especially if they are kept mainly indoors and not exposed to outside sunlight. Without sufficient vitamin D, rabbits can develop a serious condition that causes the softening of their bones and teeth. This condition is known as rickets in young kits and osteomalacia in adult rabbits.
Too Much of a Good Thing
Too much vitamin D can make a bunny seriously ill. Signs of vitamin D poisoning in a bunny include loss of appetite, diarrhea, weakness, lack of coordination, excessive thirst and paralysis. Death can occur. High amounts of vitamin D can lead to the calcification of the soft tissues inside a rabbit's body, such as her muscles, arteries and vital organs. Toxic amounts of vitamin D in rabbits were found to be around 2,300 International Units per kilogram of weight or higher. As a comparison, most rabbit diets contain a third to half of the toxic amount of vitamin D, fed according to the manufacturer's directions. This means that your bunny would have to eat two to three times the amount of pellets recommended for his weight to become poisoned.
Dangers of Vitamin D
Excess intake of vitamin D in bunnies is especially dangerous to pregnant does. In a study published in the August 2000 issue of "World Rabbit Science," scientists found that pregnant rabbits fed an excess of 10,000 IU/kg of vitamin D during the last few days of their pregnancy resulted in an almost 15 percent increase in infant rabbit fatalities. The study found that a rabbit should get between 800 and 1,000 IU/kg of vitamin D in the diet daily, with no more than 2,000 IU/kg to avoid poisoning. A dose of 600,000 IU/kg is lethal to any rabbit -- that's around 600 times a recommended daily portion of bunny pellets.
Healthy Bunny Diet
Unless your vet recommends a vitamin D supplement for your bunny, don't give her one. Feed your adult rabbit unlimited amounts of high-quality hay, which won't overload her on vitamin D. In addition, for each 6 pounds of body weight, feed your bunny 2 cups chopped veggies, a quarter-cup to a half-cup of rabbit pellets and no more than 2 tablespoons of fruit daily. This way, she'll get her proper daily allotment of nutrients. Avoid overfeeding your bunny or giving her alfalfa hay, which is high in vitamin D and fattening. Bunnies ingest vitamin D from their food and from the cecotrophs found in their feces. Obese bunnies can't reach their rear ends to ingest these cecotrophs and will become deficient in vitamins, including vitamin D.
- World Rabbit Science: Vitamins in Rabbit Nutrition: Literature Review and Recommendations
- Sherwood Forest Natural Rabbit Food: Rabbit Vitamin
- Vitamin Tolerance of Animals; Subcommittee on Vitamin Tolerance, Committee on Animal Nutrition, National Research Council
- Pediatric Research: Effect of Vitamin D on Pregnant Rabbits and Their Offspring
- Rabbit Feeding and Nutrition; Peter R. Cheeke
- Vetstreet: Rabbit Nutrition
- Textbook of Rabbit Medicine; Molly Varga
- RabbitWise: What Must I Feed My Rabbit to Keep Him/Her Happy and Healthy?
- Bright Eyes Sanctuary: The Truth About Vitamin D: Is It the Answer to Rabbit Dental Disease?
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Based in Las Vegas, Susan Paretts has been writing since 1998. She writes about many subjects including pets, finances, crafts, food, home improvement, shopping and going green. Her articles, short stories and reviews have appeared on City National Bank's website and on The Noseprint. Paretts holds a Master of Professional Writing from the University of Southern California.