Pathophysiological and Functional Aspects of the Megacolon‐Syndrome of Homozygous Spotted Rabbits

Abstract

Summary The Megacolon‐Syndrome is a hereditary disease of homozygous spotted rabbits (En En). Investigations have been performed on some special traits related to functional aspects of the gut in comparison to vital heterozygous spotted rabbits (En en). It was found that En En rabbits showed significantly reduced sodium absorption rates across the wall of the cecum. Consequently, the dry matter content of the ingesta was reduced at this location, whereas the content of the ashes was increased. These results indicate that a further important pathogenetic aspect of this hereditary disease is an undue liquification of ingesta in proximal parts of the large intestine. Severe clinical problems, however, resulted from obstipation. This is concluded to be a late complication due to and modified by different stressors of endogenic and exogenic origin. Thus there are some indications that an early site of spot‐gene related effects might be the small intestine. This segment of the bowel was shorter and had an increased dry matter proportion of its wall when compared with heterozygous spotted rabbits. But a decreased proportion of dry matter within the wall of the large intestine was found. The latter could be an effect of the hypothyreotic state of metabolism in En En rabbits.

Rabbit Genetic Resources Can Provide Several Animal Models to Explain at the Genetic Level the Diversity of Morphological and Physiological Relevant Traits

“…Other genes are probably involved in determining the degree of extension of the colored patterns versus the white areas [82]. Dominant homozygous En/En rabbits are affected by an underlying megacolon defect and are usually subvital compared to the animals with the other two genotypes, i.e., En/en and en/en [30,[82][83][84][85][86][87]. The defect has incomplete penetrance, it is influenced by environmental factors (age, diet, stressors) and is recessive, as En/en rabbits are not affected [87].…”

“…The defect has incomplete penetrance, it is influenced by environmental factors (age, diet, stressors) and is recessive, as En/en rabbits are not affected [87]. Etiopathogenetic analyses of rabbits having this megacolon pointed out that abnormalities of the enteric nervous system throughout the colon might be involved in this defect [85,86,88].…”

The KIT Gene Is Associated with the English Spotting Coat Color Locus and Congenital Megacolon in Checkered Giant Rabbits (Oryctolagus cuniculus)

“…The En/en genotype is selected for show purposes and a few breeds/strains, like the Checkered Giant and English spot, have recognized standards that are considered to result from this allele combination, even if their spotted patterns are different. En/En rabbits are subvital compared to vital heterozygous En/en rabbits because dominant homozygous animals are affected by an underlying megacolon [2] , [11] , [12] . This defect is recessive since it is not observed in En/en rabbits, and with putative incomplete penetrance, probably modified by environmental conditions (e.g.…”

“…diet, stressors and ageing) or other modifier genes. The few studies that have investigated the etiopathogenesis of this form of megacolon suggest the involvement of enteric nervous system (ENS) abnormalities throughout the colon [13] , but its characterization is still incomplete [11] , [12] .…”

The Effects of Domestication on the Brain and Behavior of the Chicken in the Light of Evolution

“…One example is the typical fur "ridge" on the back of the Rhodesian ridgeback dog breed which is associated with a mild form of spina bifida and can lead to complications (infections up to the vertebral canal and the spinal cord) [Salmon Hillbertz et al, 2007]. Another example is the spotted rabbit; special coloring is associated with a megacolon syndrome (Hirschsprung's disease) in homozygous spotted rabbits [Bödeker et al, 1995]. Furthermore, studying crested chickens and ducks provides insights into phenomena like encephaloceles and hydrocephalus [Tao et al, 2020].…”