Evaluation of gene interactions affecting carcass yield and marbling in beef cattle

• Published in: Journal of animal science 2016-09, Vol.94, p.121-122
• Main Authors: Duncombe, J L, Schmutz, S M, Madder, K M, Buchanan, F C
• Format: Article
• Language: English
• Subjects: Alleles; Animals; Beef; Beef cattle; Bovidae; Cattle; Dominance; Eye; Feedlots; Genes; Genetic diversity; Genotypes; Intensive farming; Mode of action; Ribs (structural); Single-nucleotide polymorphism; Vision; Yield
• ISSN: 0021-8812; 1525-3163

Genotype-specific management of beef cattle in feedlots has the potential to improve carcass uniformity. Gene variants affecting marbling include LEPc.73C > T, ADH1Cc.-64T > C, TG5, and GALR2c.-199T > G while those in CRHc.22C > G, POMCc.288C > T, MC4Rc.856C > G and IGF2c.-292C > T influence lean yield. The purpose of the current study was to assess combinations of marbling gene variants with those associated with lean yield. Gene variants were initially genotyped in 386 crossbred steers and evaluated for associations with carcass traits (hot carcass weight, average fat, grade fat and rib-eye area). The goal was to select a subset of variants to genotype in 2000 steers (1000 implanted and 1000 hormone free) with camera graded carcass data (vision grade USDA yield, vision grade marbling, rib-eye area and fat thickness). We selected seven gene variants to proceed with (TG was discontinued) as they either had an association or were involved in gene interactions affecting a trait. Associations between gene variants with traits were made simpler due to the fact that some genotypes could be pooled, as least squares means (LSM) were not significantly different, indicating a dominant effect of one allele. Interestingly the mode of action of a gene changed depending on the trait. For example, in the implanted steers GALR2 affected rib-eye area (P = 0.002) where it exhibited an additive effect (TT = 12.98 in2, TG = 13.07 and GG = 13.47) however there was a dominant effect of the T allele for marbling (P = 0.0001; TT/TG = 397.83 and GG = 378.27) and fat (P = 0.001; TT/TG = 8.38 mm and GG = 7.31). This same association with marbling (P < 0.0001; TG/TT 463.52 mm and GG = 430.90) and fat (P = 0.006; TT/TG = 10.23 mm and GG = 9.14) was also observed in the hormone free steers where again the T allele showed dominance. Gene interactions affecting a trait were only observed in the hormone free steers: LEPc.73C > T and IGF2c.-292C > T with fat (P = 0.05) and a trend with marbling (P = 0.07); MC4Rc.856C > G and POMCc.288C > T with marbling (P = 0.05); and GALR2c.- 199T > G and POMCc.288C > T with rib-eye area (P = 0.03). The ability to pool genotypes not only simplified the interactions, it resulted in a larger number of animals with combined genotypes. The gene SNP networks generated using EPISNP support the mode of action between gene variants. For example, the gene interaction that was a 3 by 2 was also determined to be Additive-Dominance. The gene SNP networks were affec