Fortplantning och fortplantningsproblem hos tikar av svensk och finsk lapphund : en jämförande studie

Abstract: The Swedish Lapphund is one of our eleven Swedish domestic breeds of dogs and one of Sweden’s oldest dogbreeds. The Finnish Lapphund’s origin and physical conformation is similar to that of the Swedish Lapphund. One aim of this study was to examine whether the average litter size differs between these two closely related breeds, and if so, try to find causes for this. The study has been restricted to only include the fertility of the bitch. The investigative part is based on a questionnaire survey sent to active breeders, processing of the Swedish kennel club registration forms for the period 2000-2007, and data on inbreeding and litter size from the Swedish Kennel Club's data base “avelsdata”. The results showed that the average litter size differed between the breeds in terms of number of pups born, stillbirths/euthanized pups and registered pups per litter. The Swedish Lapphund gave birth to fewer pups, had more stillborn/euthanized pups and therefore fewer registered pups per litter than the Finnish Lapphund. Fewest pups born and the highest number of stillbirths/euthanized pups per litter were seen in the bitches’ first litter in both breeds, while the largest number of pups born and registered per litter were seen in the bitches’ third or more litter. A seasonal reproductive pattern was seen in both breeds in which the largest number of pups born and registered per litter were seen in season 4 (September-November), while most Swedish Lapphund litters were born in season 1 (December-February) and most Finnish Lapphund litters were born in season 2 (March - May). Litter size had a significant negative regression (p = <0.001) on gestation length in the Finnish Lapphund. Each extra pup above the average litter size caused a shortening of the gestation length with 0.25 days, and for each pup less the gestation length increased accordingly. In the Swedish Lapphund the regression on gestation length was almost significant (p = 0.052), where each extra pup above the average litter size decreased gestation length with 0.18 days and for each pup less the gestation length increased accordingly. The average change in inbreeding coefficient during the studied period was always higher in the Swedish Lapphund compared to in the Finnish Lapphund. In conclusion, the study showed that the Swedish and Finnish Lapphunds seem to be breeds with normal reproduction. Inbreeding depression in the Swedish Lapphund is the most likely cause of the differences observed between the Swedish and Finnish Lapphund, although this vas not proven in this study. It would be interesting to study the link between individual inbreeding in specific litters and the litter size.