Reproductive demographics of the Dutch Kooiker Dog: Consequences of selective breeding in 1990-2010 on the global population
Summary
In the last two decades, von Willebrand disease (VWD) and Hereditary Necrotising Myelopathy (HNM), two genetic diseases that affect the Dutch Kooiker dog, have become a major concern within the Kooiker dog breeder communities. As a consequence, breeders implements restrictive breeding program in an effort to eliminate the diseases. It is hypothesised that the restrictive selection program resulted in an inbreeding depression due to reduced number of breeding animals. The aim of this retrospective study was to investigate the reproductive demography of the worldwide Kooiker dog population in 1990-2010 and the frequency of VWD and HNM. The reproductive characteristics investigated were: effective population, inbreeding rate and coefficients of the litters, dams and sires, litter size, the number of litters, breeding frequency of selected animals, peripartal deaths, maternal parity, maternal and paternal age at the birth of the litters. In addition, his study aimed to explore the lifespan of the Kooiker dog born in this period. Data from the Association of the Dutch Kooiker dog, comprising a total of 807 sires, 1232 dams, and 15398 puppies worldwide in 1990-2010, were analysed. Descriptive statistics were used to describe the population. The worldwide absolute effective breeding population had steadily increased since 1990. Ne was 817 animals in the five-year-interval. The mean breeding frequency for both sires and dams were approximately 4 times in every five-year-interval studied. However, the maximum breeding frequency showed some important variations. The highest rate of inbreeding (∆F) was observed in Norway (2.03%), because of a small effective population. ∆F was lowest in the Netherlands (0.19). The number of litters increased with time. The worldwide average litter size (excluding peripartal deaths) had also increased and was 5.12 ± 2.13 pups (maximum 12, n = 169 litters) in 2010. But, more medium to medium-large sized litters (4.00 to 7.00 pups) were born, when compared with a study in 1994. The high number of bitches that were bred only once may have caused the decline in litter size. The global mean inbreeding coefficient of the litters decreased from 0.07 ± 0.05 (minimum 0.00, maximum 0.26) in 1990 to 0.02 ± 0.02 (minimum 0.00, maximum 0.12) in 2010. This decline in the mean inbreeding coefficient may have been caused by the increase in the number of breeding animals. Available data suggest that the restrictive breeding program implemented in 1990-2010 has not caused an inbreeding depression in the global Kooiker dog population.