Analysis of genetic structure of Silesian horses from Ksiaz National Stud

Analysis of genetic structure of Silesian horses from Książ National Stud. The aim of the study was to analyze the genetic composition of Silesian horses bred in Książ National Stud basing on their pedigrees and to try to answer the following question: is the subdivision of Silesian horse population really necessary to prevent local horse breed? As the material 72 pedigrees of brood mares and stallions, born between 1991 and 2009 were used. On average, 93.1% of animals were inbred, there were 96.55% inbred stallions and 90.70% inbred mares. The mean inbreeding coeffi cient for all horses was 2.3%, for inbred horses it reached 2.5%. There were more inbred mares (39) than stallions (28). All 72 Silesian horses from Książ State Stud were related with the average relationship coeffi cient of 8.5%. The total and effective number of founders were 458 and 163, respectively. The total and effective number of ancestors were 64 and 22, respectively. Among the founding breeds Thoroughbred horses predominated, the next were Oldenburg and Silesian horses, whereas among ancestors there were much more Silesian horses than Thorougbreds. All in all, the genetic diversity of the Silesian horses from Książ National Stud was satisfactory, however its monitoring is required because of both upward inbreeding and 100% related animals. Because the population of Silesian horses is small, less than 2,000 animals and sligtly over 1,000 animals included in conservation programme, the artifi cal subdivision of this population as proposed in the new breeding programme, which would result in creation of 2 subpopulations: old-type and new-type Silesian horses, is not recommended. For maintaining genetic diversity, it could be also possible to carefully import of semen or stallions of similar breeds, i.e. German Alt-Oldenburger horses or German Heavy Warmblood horses. The plan should also include the matings recommended within the population of all available Silesian horses of both types. The authors consider introducing such a program essential. It should be also clearly stated in the plan how large proportion of the Silesian mares population could be each year mated to Thoroughbred stallions. Division into two types implies that some fraction of new-type Silesian horses and their progeny would not be regarded as potential parents of individuals for the conservation programme.