Browsing by Author "Wallén, Sini"

It has been challenging to genetically improve reproduction traits with the resources of the conventional breeding because of the low heritability of these traits. In Finland genetic improvement of the reproduction traits hasn’t either meet the expectations entirely. Gene markers are one possibility to make genetic improvement of the reproduction traits more effective. With an association analysis it is possible to find those gene markers which have statistically significant effect on the trait. The purpose of this study was to identify SNP markers associated with reproduction traits in the Finnish Yorkshire pig breed. Other purpose of this study was to find out if both Finnish pig breeds have certain chromosomal regions associated with same reproduction traits. In this study one goal was also to discover genes which are placed near statistically significant SNP markers. Under this study were nine female reproduction traits which are total number of piglets born in first and later parities, number of stillborn piglets in first and later parities, piglet mortality between birth and weaning in first and later parities, age at first farrowing, first farrowing interval and second farrowing interval. Prior to SNP association analysis, unstandardized EBVs were deregressed and corresponding weights were calculated. The association between SNP markers and deregressed EBV was studied using a mixed linear model, for each SNP separately. The model included a fixed SNP effect and a random polygenic effect. The analyses were performed using the AI-REML method. Statistical significance of the associations was based on Bonferroni-corrected P-values. In this study 20 statistically significant (P-value ? 2,0E-06) associations on the reproduction traits were observed. One of these SNP markers (P-value = 8,39E-08, on chromosome 7) is associated in total number of piglets born in first parity, two markers (P-values = 2,77E-07 and 1,91E-06, on chromosomes 7 and 1) in total number of piglets born in later parities, one marker (P-value = 9,72E-08, on chromosome 8) in number of stillborn piglets in first parity, three markers (P-value = 2,12E-07 and next two P-value was 7,01E-07, on chromosome 13) in piglet mortality between birth and weaning in first parity, 11 markers (P-values between 1,74E-06 and 3,89E-08, on chromosome 7) in age at first farrowing and two markers (P-values = 4,03E-07, on chromosome 7) in second farrowing interval. In this study statistically suggestive (P-value ? 4,0E-06) associations were also observed on chromosomes 1 and 8. These are associated in total number of piglets born in later parities and number of stillborn piglets in first parity. If these chromosomal regions found in this study are confirmed, these SNP markers will be valuable in the national breeding program through their use in marker-assisted selection. With MAS it’s possible to select pigs which have favourable SNP markers as for reproduction traits. In the long run genetic improvement of the reproduction traits is going to accelerate. There is still need of more extensive population analysis in order to discover genes associated reproduction traits and to estimate those gene effects.