Improvements in the porcine genetic map and availability of resource families to study performance traits in pigs have made it possible to re-examine previous findings that linked certain traits to genes or chromosomal regions. Previous studies suggested that chromosomes 4 and 7 may be associated with growth and performance traits. To confirm these previous results, an interval mapping-regression approach was used to determine whether quantitative trait loci (QTL) exist in the Iowa State University reference/resource families. Traits measured were birth weight; body weight at 21 d; weaning weight (weight at 42 d); average daily gain; backfat at the first, 10th, lumbar, and last ribs and average backfat thickness; loin eye area; meat color; marbling; and firmness. The total number of F2 pigs used ranged from 241 to 330 and came from five Chinese x American resource families. Five markers (S0001, SW871, S0175, S0214, and SW445) were genotyped and mapped on chromosome 4, and so were 10 markers (S0064, tumor necrosis factor alpha [TNFalpha], S0102, S0078, S0158, S0066, SW304, SW1083, S0101, and S0212) on chromosome 7. Data were analyzed for each family (breed cross) separately and were also pooled. Experiment-wise thresholds were used to determine significance. Suggestive evidence of QTL on chromosomes 4 and 7 was observed for several traits in pooled and individual family analyses. Suggestive evidence of a QTL with a relatively large effect for average daily gain was detected on chromosome 4 in the pooled analysis. Significant (P < .05) evidence for QTL was seen on chromosome 7 for 10th-rib, last-rib, and average backfat thickness in the pooled data set in a region of the chromosome that was near TNFalpha. These results verify in part that chromosomes 4 and 7 contain QTL for growth and carcass traits. ABSTRACT:Improvements in the porcine genetic map and availability of resource families to study performance traits in pigs have made it possible to reexamine previous findings that linked certain traits to genes or chromosomal regions. Previous studies suggested that chromosomes 4 and 7 may be associated with growth and performance traits. To confirm these previous results, an interval mapping-regression approach was used to determine whether quantitative trait loci (QTL) exist in the Iowa State University reference/resource families. Traits measured were birth weight; body weight at 21 d; weaning weight (weight at 42 d); average daily gain; backfat at the first, 10th, lumbar, and last ribs and average backfat thickness; loin eye area; meat color; marbling; and firmness. The total number of F2 pigs used ranged from 241 to 330 and came from five Chinese × American resource families. Five markers (S0001, SW871, S0175, S0214, and SW445) were genotyped and mapped on chromosome 4, and so were 10 markers (S0064, tumor necrosis factor a [TNFa], S0102, S0078, S0158, S0066, SW304, SW1083, S0101, and S0212) on chromosome 7. Data were analyzed for each family (breed cross) separately and were also pooled. Experiment-wis...
Previous research has shown that the PIT1 gene in several pig populations and the chromosomal region near PIT1 in some pig populations has been significantly associated with fatness and growth on pig chromosome 13. To confirm these previous results and to clarify the role of the PIT1 gene in controlling pig fatness and growth, this research project was focused on studying the chromosomal region close to the PIT1 gene. The ISU Chinese x U.S. pig families were used and the traits analyzed were birth weight, 21-day weight, 42-day weight, longissimus muscle area, backfat thickness at several locations, meat color, marbling and firmness on the carcass, and growth rate for selected time periods. The total number of F2 pigs used ranged from 241 to 330. Significant evidence of a genetic marker for first rib backfat thickness was detected approximately 20 centimorgans (cM) from the PIT1 gene. Evidence of a genetic marker for birth weight was detected at the estimated PIT1 position. These results confirmed the previous published research on pig chromosome 13 for the birth weight but suggest that other genes in the region may be partly responsible for the earlier results on the backfat thickness. ASL-R1574 Summary and ImplicationsPrevious research has shown that the PIT1 gene in several pig populations and the chromosomal region near PIT1 in some pig populations has been significantly associated with fatness and growth on pig chromosome 13. To confirm these previous results and to clarify the role of the PIT1 gene in controlling pig fatness and growth, this research project was focused on studying the chromosomal region close to the PIT1 gene. The ISU Chinese x U.S. pig families were used and the traits analyzed were birth weight, 21-day weight, 42-day weight, longissimus muscle area, backfat thickness at several locations, meat color, marbling and firmness on the carcass, and growth rate for selected time periods. The total number of F2 pigs used ranged from 241 to 330. Significant evidence of a genetic marker for first rib backfat thickness was detected approximately 20 centimorgans (cM) from the PIT1 gene. Evidence of a genetic marker for birth weight was detected at the estimated PIT1 position. These results confirmed the previous published research on pig chromosome 13 for the birth weight but suggest that other genes in the region may be partly responsible for the earlier results on the backfat thickness.
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