Neural Problems in Crested Ducks

Neural Problems in Crested Ducks
Reading Time: 4 minutes

What is cuter than a crested duck? Not much, unless it is an entire flock of crested ducks waddling, quacking, and socializing while showing off in their feathery pillbox hats. A favorite the world over, they have been known in Europe since the 1600s. They were depicted in paintings by Dutch artist Jan Steel around 1660, and other European painters included them in their works over the years. 

Unfortunately, their cuteness results from a genetic defect that can also cause significant neural problems. These problems may include loss of voluntary muscle control or ataxia, difficulty walking, problems standing up, difficulty getting back up once having fallen, muscular tremors, epilepsy, and even death.  

Not all crested ducks develop problems by any means, and many people keep them for years without experiencing noticeable issues. However, the development and occurrence of central nervous system disorders in these birds is still significant enough that anyone buying them or adding them to a flock should be aware of the realities they may face.  

Unlike chickens with a “top hat” or crest (in which the skull has a bony protrusion or bump under the feather crest), the skull of a crested duck does not fully close. Instead, a lipoma or lump of fat sits directly on the thin tentorial membrane covering the top of the brain. This lump protrudes through the parietal bones of the skull, inhibiting them from meeting and forming a closure. This fatty lump forms the bump or “cushion” on the top of the head just beneath the skin and is the foundation of the feather crest.

In many cases, the lipoma or fatty tissue also grows and enlarges inside of the skull as well, impeding normal brain development.

During skull formation, or craniogenesis, this lipoma impedes normal development in the developing fetus. An opening in the skull with only fatty or soft tissue protecting the brain would cause enough concern. However, in many cases, the lipoma or fatty tissue also grows and enlarges inside of the skull as well, impeding normal brain development. This intracranial lipoma can, and often does, place abnormal pressure on the brain, impeding the normal formation of the cerebellum and the attached lobes. Any or all sections of the brain may be affected, leading to severe abnormalities in neural development, seizures, and impairments in neuromuscular coordination.

According to information cited in duckdvm.com, intracranial lipomas affect approximately 82% of ducks with feather crests. While these fat bodies underneath the skull often cause skulls to be larger and have more intracranial volume than normal, the lipomas can also press against the brain, impeding brain lobes’ normal formation and function and pushing them into abnormal secondary positions within the skull. The impeding fat bodies do not only develop between the interior of the skull and the brain but may also develop between the lobes of the brain itself, placing pressure on the brain from internal positions. Postmortem examination of affected ducks shows that these lipomas may comprise less than 1% of intracranial matter or comprise as much as 41% of intracranial volume in severe cases of neurologically impaired ducks. 

Years ago, research determined that the crested trait in ducks resulted from a single, dominant gene. It also decided that this gene is fatal or deadly in the homozygous state (meaning a crested duck could only have one gene for this trait and still live). The letters Cr designate the dominant crested trait, and a simple lower case cr designate non-crested. Offspring which have two Cr genes will never hatch. These birds die during fetal development from severely malformed brains, which usually form outside of the skull. In theory, mating two crested ducks will produce 50% crested offspring, 25% non-crested offspring, and 25% which will die during incubation and embryonic formation. Mating a crested duck with a non-crested duck will, in theory, produce 50% offspring with crests and 50% with no crests. However, crested ducks from these pairings often produce crests that are less full and less showy than offspring from two crested parents, which the simple Mendelian genetic analysis and single-gene theory does not entirely explain.

crested-duck
In theory, mating two crested ducks will produce 50% crested offspring, 25% non-crested offspring, and 25% which will die during incubation and embryonic formation.

Recent research showed a high likelihood of at least four genes involved in the cresting process within ducks which may affect, at a minimum, certain fatty acid blockages and development, feather development, and the hypoplasia or incomplete skull formation within these birds. (Yang Zhang and others at the College of Animal Science and Technology, Yangzhou University, Yangzhou, People’s Republic of China, cited in the 1 March 2020 edition of Science Direct, “Whole genome re-sequencing of crested traits of expression analysis of key candidate genes in duck.”) This research may help explain part of the possible differences between crests in the offspring of two crested parents versus offspring from the mating of crested and non-crested ducks. 

Not all crested ducks will have problems, and many will not exhibit any abnormal symptoms or findings.

Crested ducks sometimes hatch with central nervous system impairments or can develop them later in adulthood. These can include ataxia, seizures, problems with eyesight or hearing, or falling over with noted difficulty in getting back up. It is not uncommon for those hatched with neural impairments to die, before reaching adulthood. Not all crested ducks will have problems, and many will not exhibit any abnormal symptoms or findings. Some may show just the slightest amount of clumsiness, which does not impair their ability to enjoy life and function in a flock with other ducks. Unfortunately, because the impairments are congenital, even the best of veterinary care from an avian practitioner may not fully correct neural problems that develop.  

Crested ducks are some of the cutest and most attractive poultry available, and they often become the favorites of those who keep them. However, anyone who chooses to raise these little fluffballs should also be aware of the potential problems and be prepared to deal with the outcomes if they should develop. Being aware and prepared is the surest way to deal with any problems if they should arise. 

Originally published in the April/May 2022 issue of Backyard Poultry and regularly vetted for accuracy.

Leave a Reply

Your email address will not be published. Required fields are marked *

[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]
[class^="wpforms-"]