Genetic Health Defects

Genetic Health Defects in Rabbits

Rabbits carry several breed-specific genetic mutations that can predispose them to health issues. Some of these are linked to coat color, body size, or skull morphology. Understanding these defects is essential for breeders and veterinarians to minimize suffering and avoid propagating deleterious traits.

Charlie Color and Megacolon

The KIT gene, responsible for the English spotting locus, is linked to both coat color patterns and congenital megacolon in Checkered Giant rabbits.

• **Genetics:**

 * Dominant allele En produces the spotted phenotype; homozygous En/En rabbits are affected by megacolon.  
 * Heterozygous En/en rabbits display standard spotted patterns without megacolon.  
 * Wild-type en/en rabbits are self-colored and unaffected.  

• **Pathophysiology:**

 * KIT gene expression in the gut, particularly in interstitial cells of Cajal (ICC), is crucial for gut motility.  
 * En/En rabbits show reduced ICC numbers and abnormalities in cecum and colon tissues, resulting in chronic constipation and megacolon.  

• **Clinical relevance:**

 * Megacolon in En/En rabbits resembles human non-aganglionic megacolon, making them a valuable model for research.  
 * Incomplete penetrance means environmental factors like diet, age, and stress can influence severity.  

• Reference:* Fontanesi, L. (2021). *Rabbit Genetic Resources Can Provide Several Animal Models to Explain at the Genetic Level the Diversity of Morphological and Physiological Relevant Traits.* Appl. Sci. 11(1):373. https://doi.org/10.3390/app11010373

Dwarf Genes and "Peanuts"

• **Double dwarf mutation:**

 * Rabbits homozygous for the dwarf allele often produce nonviable kits, known as "peanuts," due to severe developmental defects.  
 * Heterozygous rabbits appear normal but can transmit the trait to offspring.  

• Reference:* Hu, D. (2014). *Identification and analysis of the dwarf mutation in rabbits.* Epsilon Archive for Student Projects. https://stud.epsilon.slu.se/6908/11/hu_d_140622.pdf

Max Factor Genes in Netherland Dwarfs

• **Effect:**

 * Certain alleles in Netherland Dwarf rabbits result in kits born with open eyes and craniofacial deformities.  
 * These genetic variants contribute to early neonatal mortality and malformations.  

Malocclusion

• Misaligned teeth can result from inherited jaw or skull morphology defects.
• Leads to overgrown incisors, dental pain, difficulty eating, and secondary gastrointestinal stasis.

Sore Hocks

• Predisposition in breeds with narrow feet and thin fur padding.
• Results in ulceration of plantar surfaces, chronic pain, and secondary infections if untreated.

Netherland Dwarf Skull Myth

• Many claims about extreme skull shape in Netherland Dwarfs causing health problems are exaggerated.
• Morphological variation exists, but careful breeding can mitigate associated risks.

References

• Fontanesi, L. (2021). Rabbit Genetic Resources Can Provide Several Animal Models... *Appl. Sci.*, 11(1):373. https://www.mdpi.com/2076-3417/11/1/373
• Hu, D. (2014). Identification and analysis of the dwarf mutation in rabbits. Epsilon Archive. https://stud.epsilon.slu.se/6908/11/hu_d_140622.pdf
• MMC Wiki: [Malocclusion](https://mmcrabbits.com/BCWiki/index.php/Malocclusion)
• MMC Wiki: [Dwarf Genes](https://mmcrabbits.com/BCWiki/index.php/Dwarf)
• MMC Wiki: [Netherland dwarf skull myth](https://mmcrabbits.com/BCWiki/index.php/Netherland_dwarf_skull_myth)