[Possible uses of genetic markers for improving fertility and health in swine production].

Selection with regard to breeding aims can take into consideration the genotype with its effects besides the phenotype--meaning the externally visible or measurable traits. The phenotype expression of a trait depends on the underlying genotype that is modulated by environmental influences. Selection using phenotypic traits leads inevitable to inaccuracies as the genotypic effects can only be distinguished from the environmental deviations by the means of simplified statistical models. The marker-assisted selection is a method that combines the genotypic information of single genes with breeding values predicted from phenotypic information. By including the genotypic information the accuracy and intensity of selection can be improved. The selection decision can take place early in life of an animal because the time to phenotypic expression of the traits of the breeding goals has not to be bided for. The possibility of realizing selection criteria on a molecular genetic level shortens the generation interval. Particularly for fertility and health traits, this is of greatest interest. Genotyping can be performed by using blood or tissue samples of new-born piglets; it is not necessary to wait for the first parities of a sow or the results obtained by the offspring of a boar. Thus, damages and suffering from diseases can be reduced in animals, because susceptible animals can be diagnosed prior to occurrence of a disease and appropriate actions for prophylaxis can be undertaken. In the following the possibilities for pig breeding connected with marker-assisted selection are pointed out. Besides, it is shown by some examples how genes become so called candidate genes because of the physiological importance of their transcription products within the scope of metabolism. Besides the representation of the physiology of a few transcription products involved in reproductive processes results of studies analysing the association of alleles of these candidate genes with fertility traits are given.