A Study of a Fatal Feeding Flaw:Rabbit Tooth Malocclusion

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BUCKTOOTHEDBUCKTOOTHEDBUNNIESBUNNIES

Poppy“The Escape Artist”

Cuddling with her tiny kitten, Hazel, and recovering from kindling

Nibbling bread on a chilly morning

Color Genetics

•Phenotype: agouti castor

•Genotype: Aa bb Dd enen

Teeth Genetics

•Poppy is homozygous dominant for the recessive gene that causes tooth malocclusion; she is completely normal and all of her litters are and will be unaffected.

Backto family pedigree

Harley“The Chubby Bunny”

Enjoying leftover french fries and never sharing

Trying out her spotted camo on a rare snowy

day

Color Genetics

•Phenotype: broken black

•Genotype: aa Bb Dd Enen

Teeth Genetics

•Harley is homozygous dominant for the recessive gene that causes tooth malocclusion; she is completely normal and all of her litters are and will be unaffected.

Backto family pedigree

Hazel

Cuddling in the hay and trying to focus her newly opened eyes

Gobbling up french fries and looking like a walrus

Color Genetics

•Phenotype: agouti castor

•Genotype: Aa bb Dd enen

Teeth Genetics

•Because Hazel never had a litter, I will never know if she was a heterozygous carrier or just a homozygous dominant, normal-toothed rabbit.

Backto family pedigree

Scratching behind her ear while playing

Adventuring in the next box shortly after

opening her eyes

Color Genetics

•Phenotype: self color black

•Genotype:aa Bb Dd enen

Teeth Genetics

•I can never be really sure if Midnight was a carrier or not because I never saw her at an old enough age. She could possibly be a carrier of the tooth malocclusion causing gene or she could be a completely unaffected normal rabbit

Backto family pedigreeMidnight

Trying to reach the tasty grass

Eating fresh lettuce, her favorite food

Color Genetics

•Phenotype: broken blue

•Genotype: aa Bb dd Enen

Teeth Genetics

•Apple was a heterozygous carrier for tooth malocclusion; her kits can either be expressers, carriers, or normal, homozygous dominant.

Backto family pedigreeApple

Tasting grass for the first time

Nibbling on alfalfa pellets

Color Genetics

•Phenotype: self color blue

•Genotype: aa Bb dd enen

Teeth Genetics

•Sundance could have possibly been a heterozygous carrier or an unaffected homozygous dominant rabbit.

Backto family pedigreeSundance

Rye“The True Cuddle Bunny”

Only 10 weeks old and exploring his new home

Snuggled up in a towel

Color Genetics

•Phenotype: self color blue

•Genotype: aa Bb dd enen

Teeth Genetics

•Rye is an expresser of the recessive tooth malocclusion which means he is homozygous recessive and suffers from constantly growing crooked teeth

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Teeth before a checkup

Trying to get back in the nest box

Hearing the lawn mower for the first

time

Color Genetics

•Phenotype: broken black

•Genotype: aa Bb Dd Enen

Teeth Genetics

•Milo is unaffected by tooth malocclusion, but he has the potential to be a heterozygous carrier like his sister Apple.

Backto family pedigreeMilo

Exploring an old burrow, where he was actually born

Tasting hay for the first time

Color Genetics

•Phenotype: black

•Genotype: aa BB Dd enen

Teeth Genetics

•Blackberry is unaffected by tooth malocclusion, but he has the potential to be a heterozygous carrier like his sister Apple.

Backto family pedigreeBlackberry

Adventuring around a new pen after being weaned

Tasting grass for the first time with his

sister

Color Genetics

•Phenotype: black

•Genotype: aa Bb Dd enen

Teeth Genetics

•Thorn is unaffected by tooth malocclusion, but he has the potential to be a heterozygous carrier like his sister Apple.

Backto family pedigreeThorn

Will“The Runaway”

Contemplating the world outside the nest and trying the crawl over

Enjoying a tasty carrot

Color Genetics

•Phenotype: self color lilac

•Genotype: aa bb dd enen

Teeth Genetics

•Will is heterozygous for the recessive gene that causes tooth malocclusion; all of his offspring have the potential to the carriers or exhibitors or normal

Backto family pedigree

Hopping around after being reintroduced to his brother, Butch Cassidy

Gobbling up bread, his favorite snack

Color Genetics

•Phenotype: broken blue

•Genotype: aa Bb dd Enen

Teeth Genetics

•Cowboy is not an expresser of the gene, but, because he has no sired any litters, it is unknown if he is a carrier or a normal, homozygous dominant rabbit.

Backto family pedigreeSundance

Trying to stay cool in the shade

B.C. shortly after I first caught him.

Color Genetics

•Phenotype: broken lilac

•Genotype: aa bb dd Enen

Teeth Genetics

•Butch Cassidy was homozygous recessive meaning he was affected. His teeth seemed to be in worse condition than Rye’s even though he was younger.

Backto family pedigree

His teeth when I first found him

Butch Cassidy

The Current Dilemma • When she had finally given in to my constant begging, my mother never could have predicted the incredible journey my little, fuzzy, feed-store bunny would take me on. Now, nearly 6 years later, I’m one foot taller and millions more times experienced in the world of caring, breeding, and dentistry of rabbits. Once a month, I go outside wearing gawky eye goggles, face the unpredictable Mississippi weather, and proceed to trim my pet rabbit’s crooked teeth, formally known as tooth malocclusion. The three years this monthly practice has been going on, I have wondered just what caused my rabbit’s crooked teeth, and, after several accidental litters, I came across another rabbit with malocclusion, and began to wonder just what could be causing this, and so my observational experiment began.

Poppy, my very first rabbit and the mother of my first litter Rye, my first buck and the original rabbit with

tooth malocclusion

Effects of Tooth Malocclusion•With his crooked teeth, Rye has a hard time doing normal rabbit things like grooming, drinking, or even eating. Tangles and mats form in his fur because grooming is not possible, and whenever his teeth are freshly trimmed, he vigorously washes. Because of the difficulty of chewing, Rye always chooses soft, high calorie food, and methodically grinds his treats with his back molars. Drinking out of water dishes offers a new challenge, and Rye always manages to wet his entire muzzle in the process.

•To trim Rye’s quick-growing teeth, I wrap him up in a comfortable towel, wedge open his mouth with my fingers, and begin to trim down his teeth. Even though I put him through this seeming torture every month, Rye has remained the friendliest rabbit in the pen, and is always eager to be cuddled or trimmed.

Before his tooth checkup After his tooth checkup

Using the Scientific Method

• Before beginning the experiment, I needed to set up my information according to the scientific process which requires research to be conducted, a question to be asked, a hypothesis to be formed, and a conclusion to be drawn.

• The Research is depicted on the following slides

• The Question: What is causing malocclusion in my rabbit’s teeth?

• The Hypothesis: If a rabbit inherits the homozygous recessive gene from its heterozygous carrier parents, then it will be affected by tooth malocclusion.

• The Conclusion will be formed after further observation study of the hypothesis

Research Step 1Studying genetics and other influences

• TEETH- For years, rabbits have been used by researchers and geneticists because of their ease of care, short procreation, and startling chromosomal similarities to humans. As different breeds developed and led to the constantly growing pet rabbit trend, inbreeding and other genetic shortcomings spawned tooth malocclusion, causing people to wonder just how their “peter cottontail” became a tusky, grumpy tasmanian devil. Researchers began to the study the gene and have recently come up with several conflicting reasons, so I decided to make a hypothesis and test it.

• COLOR- Rabbit fur coloring is controlled by 10 or so recognized allele groups. In my study, however, I decided to only focus on the 4 following allele sets.

Gene Descriptions Dominant Allele Recessive Allele

Agouti/Self Color A a

Black/Brown B b

Dense/Dilute D d

Broken/Self Colored En en

• Using my education from ninth grade biology and the internet, I began to study my own notes and tried to decipher genetic or environmental connection in the inheritance of tooth malocclusion. I had personally raised one of the other rabbits who was an expresser of the gene, so I could rule out nutritional deficiencies as being a cause. As I began to look for other answers, I also noted that both expressers I had experienced were male, making me ponder the possibility of a sex linked trait, but then, it hit me! Tooth malocclusion followed the exact pattern that any recessive gene would follow in a family tree.

• Rye, my original rabbit with tooth malocclusion, would be homozygous recessive; his kits, Apple and Will, would be heterozygous carriers. When they escaped and I found their accidental litter four weeks later, I caught two of the kits. One was completely unaffected, but the other was homozygous recessive for tooth malocclusion, confirming his sire and dam as carriers of the sometimes deadly gene. The alleles included in my recessive gene hypothesis for tooth malocclusion are pictured below.

Phenotype Genotype Normal?

homozygous dominant TT normal

heterozygous Tt carrier

homozygous recessive tt expresser

Research Step 2Organizing my own information

RyePoppy Harley

Hazel Midnight Will Apple Blackberry Thorn Milo

Butch Cassidy Cowboy Sundance

KeyKey

male known carrier

female normal

expresser untested potential carrier

The Family Tree

CLICK ON ANY RABBIT TO GO TO A

PERSONALIZED PAGE OF INFORMATION

Hypothesis and Explanation

• The before stated hypothesis is supported by the pattern of inheritance show in the family tree. By skipping one generation and revealing itself in the next, the gene for tooth malocclusion is very similar Mendel’s famous purple and white peas. These recessive genes, as Mendel dubbed them, can be carried for generations without appearing.

• In my personal experiment, the recessive genes appeared after only 1 generation. Rye, a homozygous recessive, passed on one recessive allele to his offspring making them heterozygous carriers. When the heterozygous carriers bred, another homozygous recessive rabbit, Butch Cassidy, reveled itself.

Conclusion• As I went along in my researching for other causes, I became more and more certain that tooth

malocclusion in rabbits in caused by a recessive gene. Several research groups have done studies supporting this hypothesis, and controlled experiments have shown that nutritional and environmental conditions have little or no affect on tooth malocclusion. Different breeds are more or less susceptible to this fatal disease, but smaller breeds such as Mini Rexes are at a much higher risk.

• Learning about rabbit genetics opened my eyes to the detailed genes that combine to create a small, furry creature. With 42 chromosomes, rabbits can teach us a great deal about our own genetic history and possibly explain our dental malocclusion too.

Sources• During my research, I used the following sites and books to learn more about rabbit genetics and

tooth malocclusion:

• http://jorthod.maneyjournals.org/content/26/3/195.full

• Rabbit Production by Steven D. Lukefahr

• http://www.ufaw.org.uk/DENTALMALOCCLUSIONNETHERLANDDWARF.php

• http://www.bio.miami.edu/hare/dental.html

• http://www.doubledeckerrabbitry.com/rabbit_color_genetics

• http://www.debmark.com/rabbits/genetics.htm

• http://rabbitgenetics.weebly.com/index.html

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