Abstract
Abstract Embryonic development in mammals is strictly controlled. Yet, anomalies regularly occur within certain species. The pig is one of few species where variation in vertebra numbers frequently occurs. Domesticated lines typically have a greater number of thoracic and/or lumbar vertebra than the number of vertebrae in most mammals. Number of functional teats is also variable in swine and deviation from bilateral symmetry is common. Positive genetic correlations between these two traits have been reported and a gene variant in vertnin affects both traits. To further investigate the genetic correlation between teat counts and vertebra numbers, a genomewide association study was conducted using 5,939 genotyped animals from the USMARC population representative of commercial swine. All animals were genotyped with one of four different Illumina-based BeadChips. Genotypes were imputed for 71,634 markers using pedigrees with findhap. gEBV were estimated and marker effects backsolved using WOMBAT. The vertnin region had the greatest number and most significant associations for all traits analyzed. However, there were no other significant associations that overlapped between vertebra and teat number. Correlation among all estimated marker effects between vertebra and teat number was ~0.21. However, if estimated SNP effects for markers surrounding vertnin were removed, the correlation dropped to 0.14, while the correlation among marker effects in the vertnin region was ~0.90. Genomic heritabilities for teat and thoracic number were 0.36 and 0.78. Analyses where the GRM only included markers surrounding vertnin estimated heritabilites for teat and thoracic number of 0.05 and 0.48, indicating vertnin described a majority of genetic variation for rib number but much less for teat number. Genetic and phenotypic correlations among weight traits and vertebra number were near zero. A positive phenotypic association between teat number and birth weight existed despite a low negative genetic correlation. USDA is an equal opportunity employer.
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