Population structure and genetics of longevity in a colony of dog guides

The objectives of this study were the description of changes in genetic diversity in a colony of dog guides since its founding, and the investigation of the genetics of longevity in that population. Two breeds of dog, German Shepherds (GS) and Labrador Retrievers (LR), were evaluated. There were rapid increases in average pairwise relationship in both breeds, although the average was approximately one-third higher in the GS population than in the LR population. A similar trend was observed for average inbreeding. In the current generation, relationship and inbreeding for all animals averaged 25.3% and 26.2% in GS and 15.5% and 22.0% in LR, respectively. Effective founder numbers initially decreased in GS until generation 3, and then increased steadily. There was a constant increase in effective founder number in LR after founding. A similar pattern was seen for effective ancestor number as well. Founder genome equivalents were initially higher in the GS but decreased over time in both breeds. New breeding stock should be imported in order to reduce the levels of inbreeding and relationship in this colony. Data on longevity for 1,403 GS and 1,816 LR dogs who worked as guides were used to estimate genetic parameters for working life. Two measures of working life were considered: working life to 18 months post-graduation (EWL) and working life beyond 18 months post-graduation (LWL). Survival analysis was used to estiamte the sire component of variance and estimated breedinb values (EBVs). Linearized heritability estimates were small: 0.032 and 0.045 for EWL and 0.016 and 0.032 for LWL in GS and LR, respectively. Genetic trend was estimated by regression of EBVs on year. No trend was observed for either trait in either breed, suggesting that historical selection criteria were not effective in improving working life. An antagonistic relationship may exist between aptitude for guide work and risk of culling for temperament