[The problems of breeding spotted rabbits. 3. Variability of the pigmentation grade, ganglionic intestinal wall supply, relationship to pathogenesis--animal breeding and animal welfare aspects].

In a total of 128 animals of the German Giant Spot und the English Spot Breed grade of pigmentation and spotting pattern were investigated by photography and planimetry. A clear cut binary distribution, representing homozygous (KK) or heterozygous spot rabbits (Kk), and a strong bilateral concordance was found as well as a broad variance within both genotypical groups. Thus only a small percentage of animals bred can be compatible with mandatory fancy breed standards. Measurements of intestinal layers and neural components in well pigmented and depigmented individuals revealed an enhancement of these histological structures but a relative hypoganglionosis in distal parts of the gut in animals with predisposition to megacolon (KK, so-called chaplins). It is not yet clear whether this is symptomatic or of primary pathogenetic relevance. There were no pleiotropic deleterious effects of the K-allele in heterozygous rabbits and no correlations between the degree of depigmentation and the severity of symptoms in homozygous spotted ones, thus indicating a mode of inheritance by an incompletely dominant gene K, acting as or being linked to a recessive semilethal when homozygous. A change in breeders' attitude and breeding practices is mandatory because neither the permanent elimination of animals not "fitting" a fancy standard nor the continuous production of defective genotypes is legal.