Date of this Version
Selection for improved sow lifetime reproductive longevity is of growing importance to swine producers due to recent increases in sow culling rates. Traditional selection results in minimal response due to low heritability and late expression of the trait; incorporation of DNA markers into selection programs could be a more economically viable tool and improve lifetime reproductive performance.
In order to assess the relationship between markers and reproductive longevity, 967 gilts from two maternal crossbred lines were evaluated for age at puberty (AP), litter size traits, and number of successful parities (SP). Females were culled only for death, unsoundness, or reproductive failure. Gilts that reached puberty by 240 days of age were designated as breeders and genotyped for 62,183 SNPs. Genome-wide association studies employing Bayes C and B approaches were performed for AP, SP and litter traits.
Eleven 1 Mb regions associated with AP explained the largest proportion of phenotypic variation in AP. The represented regions included SSC1 (88 and 269 Mb), 2 (60 Mb), 3 (14 Mb), 4 (6 Mb), 5 (27 Mb), 6 (85, 111 Mb), 8 (30 Mb), 9 (119 Mb) and 12 (1 Mb). One region (SSC12, 1Mb) overlapped with a top region identified for SP and lifetime litter size. A significant negative correlation was shown between AP and most of the lifetime litter traits recorded, indicating that an earlier AP would result in higher reproductive performance.
Functional annotation and analyses of regions associated with phenotypic variation in AP revealed candidate genes including PAPPA (SSC1) that influences follicular differentiation in swine, CRTC1 (SSC2), found to be associated with puberty onset in humans, CRHBP (SSC2), playing a role in the regulation of the hypothalamic-pituitary-adrenal axis, AVPR1A (SSC5), a G-protein coupled receptor associated with social and reproductive behaviors and PRKAA2 (SSC6), a catalytic subunit of AMPK, a sensor of energy metabolism. The incorporation of identified functional mutations and markers into a breeding program can potentially be used to predict age at puberty and improve sow productivity and longevity.
Advisor: Daniel Ciobanu