Polymelia in broiler

A polymelus monster was observed in farm mainly described as Polymelia is a birth defect involving limbs (a type of dysmelia), in which the affected individual/animal has more than the usual number of limbs. In poultry upto 3 legs has been observed but this has four legs and the point to be noted that it has survived for five weeks and still alive. The extra limb is most commonly shrunken and/or deformed but not in this case as it too looks healthy the bird has also two anus.

The reason it happen as sometimes an embryo started as conjoined twins, but one twin degenerated completely except for one or more limbs, which end up attached to the other twin. Sometimes small extra legs between the normal legs are caused by the body axis forking in the dipygus condition. The external features showed two normal limbs and two developed extra-limb. This extra-limb was attached to the caudal region of the pelvic bone and was surrounded by a mass of muscular tissue. The extra-limb was formed at a joint with the pelvis, presenting a characteristic duplicated femur and tibia. This phenomenon is very rare in chickens and bird grow and survive at this stage is near to impossible.

These anomalies are usually associated with genetic factors including transgenes, chromosomes, and environmental agents including infectious agents, toxins, techniques involved in fertilization and certain management factors or a combination of factors (Keeler et al., 1981; Rousseaux and Ribble, 1988; Newman et al., 1999). Such anomalies have also been associated with excessive division as seen in related problems such as polydactyla (supernumerary fingers or toes), polythelia (Supernumerary nipple) and polydontia (having more than the normal number of teeth) (Rahman et al., 2006).

As at present, there is no definitive etiologic knowledge of its origin. The understanding as to whether it is caused by genetic or environmental factors, or both, is not clearly known but it is confirmed that the susceptibility to an injurious environmental factors or to certain genetic agents varies with the various stages of bone development between species (Rahman et al., 2006). This could be a notable cause of this condition in chickens.

To the best of our knowledge, this is the first report of a notable case of polymelia in chickens in India as i haven't found any reference yet if it seen before can be discussed in the discussion.