Cerebral Hernia

From the Dutch Poland Club

By Peter Jones

Breeders of fowl the world over have reported a condition that seems peculiar to crested breeds, particularly birds with heavier crests than others. The onset of the condition is described as a wobble in the head which can increase in severity to the point where the head twists right around. . In some cases the bird looses its balance and mobility altogether. This is commonly called ‘cerebral hernia’.

The Victorian Institute of Animal Science has conducted post mortems on breeds such a Polish and Silkies over the years. They confirm the existence of a mutation in the dominant gene for a crest. A mutation is a genetic copying error or mistake that occurs when the DNA from the parent bird’s meet and divide incorrectly in what is known as meiosis.

The skull of a crested fowl is unique. Unlike other breeds, it is dome-like in structure and, in heavily crested chicks, there is a tendency for the skull to be underdeveloped. Like the fontanels of a human baby, the skull of crested fowls has openings.

These are supposed to fuse in the normal way and usually do. However, this does not always occur and the result is exposure of the cerebellum (brain). Subsequently, a bird’s brain space remains venerable to the environment.

Certain lines seem more predisposed to this condition, whereas other lines are seldom affected. Unsurprisingly, it is rare in adult birds, as their skulls have had the time to grow and fuse over. It is more prevalent with young birds between 1 and 4 months of age.

Conditions and treatment.

Fortunately, the problem is not common. Edan Montgomery claimed that out of over 600 birds bred last year, about 5-6 developed the condition. Sadly, it is usually the heavily crested potential champs.

By hatching in large numbers, line breeding rather than close in breeding, and practicing good management techniques, this condition is largely avoidable. Every breed has its hiccups. For crested breeds, this is one of them.

On a positive note, the rewards of producing a champion far outweigh the occasional disappointment linked with this condition. It also goes to show the largely detrimental nature of mutations. They are rarely if ever an advantage!

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