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2010-2011 Winter Issue - the American Dwarf Hotot Rabbit Club

2010-2011 Winter Issue - the American Dwarf Hotot Rabbit Club

Genetic

Genetic Issues One Encounters When Breeding Dwarf Hotots By Joyce Holton Raising Dwarf Hotots is anything but dull. More often than not, the nest boxes are full of surprises. Aside from the typical stray black spot or missing eyebands, one surprise we may encounter will be a kit with a genetic mutation. Peanuts Peanuts appear very small as compared to their siblings and have heads that seem too large for the body. This condition, known as dwarfism, is caused by the dwarfing gene Dw. This dwarfing gene can be found in the Netherland Dwarf, Dwarf Hotot, Holland Lop, American Fuzzy Lop and Mini Rex breeds. Dwarfism will occur when both parents pass on one of the Dw dwarfing genes resulting in the DwDw combination. This combination of double dwarf genes is lethal to the rabbit and, if born alive, will not survive more than a few days. Peanuts are normally culled as they will never survive. The following Punnet Square demonstrates how the lethal DwDw gene will present itself 25% of the time when two rabbits carrying the dwarfing gene are crossed. Dw dw Dw DwDw (Lethal Dwarf) Dwdw (Desired) dw Dwdw (Desired) dwdw (BUD) The correct dwarf body type we want to see is Dwdw. The Dwdw combination, containing only one Dw dwarfing gene, will occur 50% of the time, creating the body type we all hope to find in our litters. On the contrary, 25% will inherit the dwdw combination, creating the false dwarf, or the dwarfs with the longer body type and ears commonly referred to as BUD’s (Big Ugly Does). The double dwarf gene, DwDw, is the lethal combination responsible for the peanuts. As breeders of dwarfs we should expect to find peanuts in our litters. The lack of peanuts will indicate the absence of the dwarf gene in the mating pair. As you can also see from the Punnet square above, the pairing of two BUD’s (dwdw) will never produce the desired dwarf typed rabbit. At birth it is impossible to determine the BUD from the normal Dwarf Hotot. The difference in size will become more noticeable as they grow and mature as seen in the photo above of the two 15-week old siblings side by side. The rabbit on the right is the desired dwarf size and the rabbit on the left is a BUD. Max Factor Another genetic mutation appearing in the dwarf breeds is the Max factor. The term Max Factor was given to the gene that was linked to a German buck known as Max. Max was imported to the United States in 1975. It is believed that the Max factor is a normal recessive gene. Both parents must carry the gene in order for it to be passed to the offspring. If the Max factor gene is identified as Mx, the following Punnet square demonstrates how each parent will give one mx gene to the baby to produce the mxmx Max factored baby. Winter 2011 Dwarf Hotot News Page 45

Mx mx Mx MxMx (Non Carrier) Mxmx (Carrier) mx Mxmx (Carrier) mxmx (Max Factored Baby) Max factor kits are not the same as peanuts. The Max factor and the lethal double dwarf are not the same thing nor are they from the same gene. It is possible for some kits to have both the double dwarf genes and the Max genes. The Max factor is not necessarily lethal unless the dwarfing gene (DwDw) is also inherited. Although Max factor kits may survive, culling these kits would be the most humane treatment. Certain traits identify the Max factored kit. These kits will often be born with one or both eyes open and appear black as seen in the photo on the left below. Most Max factored babies will be blind. If the baby lives it will be susceptible to weepy eyes and eye infections as a result of being born with the eyes open. Max Factor kit with eyes open at birth Blind Max baby Weepy eyes Another trait of the Max factored baby is the deformity of the legs. The rear legs may be positioned awkwardly at birth. The legs will be turned inward and the feet turned outward at a sharp angle or parallel to the legs. The feet may also be flattened like flippers. These are known as “frog babies.” In some cases the front legs may also show deformities and the rear feet may have extra toes. The abnormal position of the feet and legs will force the rabbit to waddle on the hocks, which may eventually lead to sores and infections. Even though the baby was blind and deformed he learned to adapt quite well to his environment. He was able to move around the cage without any trouble and found the food and water easily. The fur of the Max Factor baby appears different than that of a normal Dwarf Hotot. Unlike normal fur, the Max factor fur is slightly wavy. It is longer and the texture appears course but is actually very soft to the touch due to the lack of guard hairs. The length of the fur between the ears gives the ears the appearance of being shorter. With some careful planning and selective breeding you can look forward to maximizing the number of desirable Dwarf Hotot babies in your spring nest boxes! May they all be full! Winter 2011 Dwarf Hotot News Page 46

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