Identification of quantitative trait loci affecting birth characters and accumulation of backfat and weight in a Meishan-White Composite resource population

A search for genomic regions affecting birth characters and accretion of we ight and backfat was conducted in a Meishan-White Composite reciprocal back cross resource population. Birth traits analyzed (n = 750) were Vigor score , number of nipples, and birth weight. Subsequent measures on gilts and bar rows (n = 706) analyzed were weaning weight, 8-wk weight, ADG from 8 to 18 wk of age, ADG from 18 to 26 wk of age, 26-wk weight, and backfat over the first rib, last rib, and last lumbar vertebrae at 14 and 26 (n = 599) wk of age. Feed intake and growth of 92 individually penned barrows were also an alyzed. A genomic scan was conducted with microsatellite markers spaced at approximately 20-cM intervals, a least squares regression interval analysis was implemented, and significance values were converted to genomewide leve ls. No associations were detected for traits measured at birth except for n umber of nipples, where one significant and two suggestive regions were ide ntified on chromosomes (SSC) 10, 1, and 3, respectively. Early growth was a ffected by a region on SSC 1 as evidenced by associations with weights coll ected at weaning and 8 wk of age and ADG from 8 to 18 wk of age. Other regi ons detected for early growth rate were on SSC 2, 12, and X. Chromosomal re gions on SSC 6 and 7 affected ADG from 18 to 26 wk of age. All measures of backfat were affected by regions on SSC 1 and X, whereas SSC 7 consistently affected backfat measures recorded at 26 wk of age. Suggestive evidence fo r QTL affecting backfat at 14 wk of age was also detected on SSC 2, 6, 8, a nd 9. These results have improved our knowledge about the genetics of growt h rate and fat accretion at the molecular level in swine.