The use of conventional radiography and computer-assisted tomography as instruments for demonstration of gross pathological lesions in the cranium and cerebrum in the crested breed of the domestic duck (Anas platyrhynchos f.dom.).

According to literature reports, the crested breed of the domestic duck (Anas platyrhynchos f. dom.) is described as a variety with high pre- and post-natal mortalities, malformations in skull and brain anatomy, and various central nervous deficiencies in affected birds. A detailed examination as to the cause and pathogenesis of these neurologic disorders has not yet been conducted, nor has an explanation concerning the inheritance of the feather crest been found. By using two non-invasive radiographic techniques, conventional radiography and computer-assisted tomography, living ducks were examined. Our studies have demonstrated that brain and skull anatomy of ducks of various breeds (Crested, Abacot Ranger, and German Pekin) can be well visualized using computer-assisted tomography. The Crested ducks investigated in this study showed abnormal fatty tissue deposits in the tentorium cerebelli, cranial malformations, and variable bone formations in the thickened hypodermis of the crest. In comparison with computer-assisted tomography, only parts of the skull changes were detected with conventional radiography; in no case could fat bodies be seen with this imaging method. An increase of the cranial capacity in the Crested ducks compared with other breeds examined (Abacot Ranger, German Pekin ducks) was found in morphometric studies carried out by computerassisted tomography. This increase of cranial capacity in Crested ducks results from an increase of the tentorial fatty depot during craniogenesis, as an enlargement of the fat body can influence cranium growth as long as the cranial bones are not yet fused. Thus, in comparison with other phenotypically similar domesticated birds like the crested chicken, the expression of the feather crest in domestic ducks demonstrates symptomatologic differences.

Osteological investigations of the incidence of cranial alterations in domestic ducks (Anas platyrhynchos f. dom.) with feather crests.

The feather crest of the domestic duck (Anas platyrhynchos f. dom.) represents a peculiar mutation of the integument of the head, which has been known since the 17th century. In literature this is described as a variety with malformations in skull and brain anatomy in which various central nervous deficiencies in affected birds are possible. Our examinations demonstrated several conspicuous anatomical alterations in the skulls of domestic ducks with feather crests. Osteophytes of different size in the hypodermis of the crest integument were found as well as cranial perforations located in the parieto-occipital region. In morphometric studies, a significant increase in the capacity of the cranium was found in Crested ducks compared to other examined breeds (Abacot Ranger, German Pekin ducks). This increase in cranial capacity in Crested ducks results from the occurrence and enlargement of a tentorial fatty depot during craniogenesis. The formation and enlargement of the fat body can influence cranium growth as long as the cranial bones are not entirely fused. Thus, in comparison to other phenotypically similar domesticated birds like the crested chicken, the expression of feather crests in domestic ducks demonstrates symptomatologic differences. In conclusion, our examinations demonstrate that the skulls of Crested ducks show various peculiar morphological alterations whose genesis is up to now not known with satisfactory accuracy. Further investigations are continuing to assertain whether there are linkages between cranial alterations (malformations of the calvaria, osteophytes, increased capacity of the cranium) and the extremely high prenatal and postnatal mortalities and numerous abnormalities described in crested breeds of the domestic duck.

[Preliminary examinations on the effects of the breed characteristic feature "feather crest" on skull and brain anatomy of domestic ducks (Anas platyrhynchos f. dom.)]. / Voruntersuchungen zur Auswirkung des Rassemerkmales "Haube" auf die Schädel- und Hirnstruktur bei Hausenten (Anas platyrhynchos f. dom.).

As mentioned in older sources, the crested breed of the domestic duck is described as variety with high pre- and postnatal mortalities, malformations in skull and brain anatomy, and several central nervous deficiencies in affected birds. Therefore this breed is to be called defective and abnormal in the sense of section 11b of the German protection of animals legislation. Poultry fanciers reject these findings as incorrect, but accurate scientific examinations that bear out this allegation are not available. Preliminary examinations have demonstrated that brain and skull anatomy of living animals can be described by using non-invasive diagnostic techniques (magnet-resonance-imaging, computerized tomography, radiography). The use of this progressive methods enables to expressive findings on present stocks of domestic ducks. Many of the test animals investigated in preliminary examinations by using magnet-resonance-imaging and radiography showed abnormal tissue deposits in the tentorium cerebelli, meningo-encephalocele, cranial malformations, and variable bone formations in the thickened hypodermis of the crest. If crested ducks are mated against each other, numerous offspring show malformations of upper beak and cranium, encephalocele, as well as craniopagal parasites in form of rudimentary legs.

Ataxia and disequilibrium in domestic ducks (Anas platyrhynchos f. dom.) with intracranial lipomas.

Four birds in a flock of 125 purebred Crested ducks (Anas platyrhynchos f. dom.) had cerebellar signs of unknown etiology. They had radiographically evident perforations of various sizes in the parieto-occipital calvaria. Gross necropsy of euthanatized ducks revealed yellow intracranial masses in the brain of each. Histologically, these masses were intracranial lipomas consisting of univacuolated fatty tissue separated into lobules by strands of connective tissue. The masses had caused serious deformation of the rostral part of the cerebellum, leading to a nearly complete flattening of cerebellar folia, and were interpreted as the cause for the central nervous clinical signs observed. These intracranial lipomas were similar to those previously reported in other animals and humans.

Magnetic resonance imaging of intracranial tissue accumulations in domestic ducks (Anas platyrhynchos f. dom.) with feather crests.

The crested breed of domestic duck (Anas platyrhynchos f. dom.) has been described as a variety which has high pre- and postnatal mortalities, malformations in skull and brain anatomy, and several central nervous deficiencies. In addition, intracranial tissue accumulations have been diagnosed in purebred Crested ducks. The incidence, heredity and inheritance of these accumulations as well as their pathogenesis are still generally unknown. The aims of this study were to examine the head of Crested ducks, plain-headed duck breeds, and their crossbreeding relating to the incidence of intracranial alterations. These examinations were performed using magnetic resonance imaging. We found a high incidence of intracranial tissue accumulations in domestic ducks with feather crests. Creasted ducks had more intracranial tissue deposits than plain-headed ducks (p < 0.001). In the present study a correlation between the volume of the crest cushion and the volume of the intracranial tissue deposit could not be found (r = 0.014). Some of the Crested ducks had encephaloceles in addition to the crest cushion.