Analysis of systematic effects on congenital sensorineural deafness in German Dalmatian dogs

We have analysed the systematic influences, phenotypic colour markers and the additive genetic variation for congenital sensorineural deafness (CSD) in German Dalmatian dogs in order to help elucidate the importance of phenotypic breed characteristics for genetic differences of CSD. Linear animal models using restricted maximum likelihood methods were employed to estimate variance components. Data were obtained from all three German Dalmatian kennel clubs associated with the German Association for Dog Breeding and Husbandry (VDH). CSD was recorded by standardized protocols for brainstem auditory-evoked response (BAER). The material included 1899 German Dalmatian dogs from 354 litters in 169 different kennels. BAER testing results were from the years 1986 to 1999. Pedigree information was available for up to seven generations. The animal model regarded the fixed effects of sex, coat colour, eye colour, presence of patches, litter size, percentage of examined puppies per litter, kennel club, and inbreeding coefficient. The common environment of the litter and kennel as well as the additive genetic effect of the animal were taken into account as randomly distributed effects. The fixed effects of eye colour, percentage of puppies examined per litter and kennel club were significant in the mixed model analysis. A significant proportion of additive genetic variation could be shown despite corrections for phenotypic colour variants. The heritability estimate for CSD in German Dalmatian dogs was h(2)=0.27+/-0.07. The additive genetic correlation of CSD with presence of blue eyes was r(g)=0.53+/-0.41 and with presence of patches r(g)=-0.36+/-0.24. We concluded that additional genes other than those associated with phenotypic colour markers in German Dalmatian dogs significantly contribute to the occurrence of CSD.