|Tait, Richard - Geneseek Inc, A Neogen Company|
|King, David - Andy|
|Smith, Timothy - Tim|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2018
Publication Date: N/A
Interpretive Summary: Some genetic markers with moderate to large effects have potential benefits for improved beef production. Recently discovered markers often are not well characterized for recessive and interaction effects or on both productive and reproductive performance. Two genetic markers previously identified as potentially beneficial based on carcass and meat traits were tested for possible interactions and recessive effects. Results found that the marker previously associated with increased muscle and leanness had about half the effect of the markers causing the double-muscling phenotype. This marker showed mostly additive effects, meaning that animals with two copies of the allele were twice as different as those with a single copy. This marker also disrupted another marker usually associated with meat tenderness. Better estimates of these markers effects on meat, muscle, and leanness should improve the ability to use them especially for lean beef production.
Technical Abstract: The objective of this study was to enhance estimates of additive, dominance, and epistatic effects of a genetic marker and a marker haplotype on beef carcass and quality traits. These markers had previously been associated with fat and muscle traits in beef cattle (growth differentiation factor 8 [GDF8; myostatin] F94L and the mu-calpain [CAPN1] 316 and 4751 marker haplotype). Multiyear selection in a composite population segregating these markers increased minor allele and desired haplotype frequencies to intermediate levels resulting in estimates of additive and non-additive genetic effects with more precision. During the 3 years following selection, 176 steers were evaluated for growth, carcass, meat quality, tenderness, and meat color traits. The statistical model included year, age of dam, age of the steer, and genotype in a random animal model. The 9 genotypes (3 CAPN1 diplotypes × 3 F94L genotypes) affected marbling score, ribeye area, adjusted fat thickness, vision yield grade (all P = 0.001), slice shear force (P = 0.03), and light reflectance (P = 0.01). Linear contrasts of the 9 genotypes estimated additive, recessive, and epistatic genetic effects. Significant additive effects of the F94L L allele decreased marbling score, adjusted fat thickness, vision yield grade, and slice shear force; and increased ribeye area and light reflectance. Differences between the divergent F94L homozygotes were 0.8 to 0.9 phenotypic SD for light reflectance and slice shear force and 1.3 to 1.9 phenotypic SD for carcass traits but carcass weight differed by 3 kg (0.1 SD). The L allele was partially recessive to F for ribeye area (P = 0.02) and the other carcass traits tended to be closer to the FF genotype than the LL genotype, but differences were not significant. The CAPN1 additive × F94L additive effect on slice shear force was the only significant epistatic estimate. The F94L L allele is prevalent in Limousin but nearly absent in other U.S. purebreds. This allele had about half of the effects on birth weight, muscle, and fat traits reported for disruptive GDF8 mutations in Belgian Blue F2 progeny produced at the same location with similar management and a Piedmontese F2 population. Its strong additive effects for fat and muscle traits and moderate effect on meat tenderness may interfere with the usual relationship often found between CAPN1 and meat tenderness.