|Tait Jr, Richard|
|King, David - Andy|
|Smith, Timothy - Tim|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 2/23/2013
Publication Date: N/A
Technical Abstract: The objective was to improve genetic marker effect estimates of SNP previously associated with muscle traits in beef cattle (F94L marker in GDF8 and 316 marker of CAPN1). Multiyear selection in a composite population segregating both SNP increased minor allele frequency (MAF) to intermediate levels that are more optimal for estimating additive and nonadditive genetic effects. Final MAF of the lysine-encoding allele of GDF8 (allele L), and the C allele of CAPN1 316 were 0.43 and 0.44. During 3 consecutive years following selection, 176 steers were evaluated for carcass, meat quality, tenderness, and meat color traits. Analyses adjusted traits for age at harvest. The 9 genotypes (3 CAPN1 316 X 3 F94L) affected marbling score, ribeye area, adjusted fat thickness, Vision Yield Grade (all P < 0.001) and L* reflectance (P = 0.02). Contrasting the estimates for the 9 genotypes for additive, recessive, and epistatic effects associated with the two SNP showed significant (P < 0.001) additive effects of F94L allele L for decreased marbling score, adjusted fat thickness, and Vision Yield Grade and increased ribeye area and L* reflectance. Differences between FF and LL genotypes were 1.9 to 2.4 RSD for these traits except L* reflectance (1.0 RSD difference). These differences did not reflect the small, nonsiginificant difference in carcass weight of 4 kg (0.16 RSD). The F94L L allele tended to be recessive to F for marbling score (P = 0.08) and ribeye area (P = 0.05). Contrasting CAPN1 316 estimates did not detect significant or suggestive additive, recessive, or epistatic effects for any trait, including tenderness measurements. The F94L L allele, prevalent in Limousin but nearly absent in other U.S. breeds, had 1/2 to 2/3 of the effects found for GDF8 mutations in Belgian Blue and Piedmontese, and has strong additive effects for fat and muscle traits that may obscure any relationship of CAPN1 with tenderness. Intermediate frequencies following selection contributed to accuracy of genetic effect estimates.