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Other Names: Four-legged Chicken
Polymelia is a genetic birth defect and type of congenital malformation of the limbs that can sometimes occur in chickens, and is defined as the growth of additional limb(s) attached to various body regions. The additional limb or limbs are often shrunken in size and/or deformed. The exact cause of this congenital anomaly is unknown, however it is thought to be associated with genetic factors involving transgenes, chromosomes, and/or possible exposure to environmental toxins.
Case 1: Polymelia in a Hen A 7-month-old layer Fayoumi chicken had two pericloacal extra limbs located caudal to the normal ones in an inverted position. The extra limbs were immovable and loosely attached to the underlying tissues. The supernumerary limbs had normal skin with ill-developed feathers. The extra limbs were fused proximally and crossed distally. Plain radiographic examination showed unequal numbers of bones and digits in both extra limbs. The right extra limb had a femur and tarsometatarsus while the left extra one had femur, tibiotarsus, and tarsometatarsus bones. The extra limbs appeared smaller than the normal ones and had neither muscles nor tendons. Amputation of the extra limbs under local infiltration analgesia was easy, safe, and curative. Ref