No abstract

. 2004. Heritability and correlation estimates of Warner-Bratzler shear force and carcass traits from Angus-, Charolais-, Hereford-, and Simmental-sired cattle. Can. J. Anim. Sci. 84: 599-609. Heritabilities and correlations of Warner-Bratzler shear force (WBSF), marbling score (MS), hot carcass weight (HCW), 12-13th rib-fat (FAT), and ribeye area (REA) were calculated from 3360 Angus-, Charolais-, Hereford-, and Simmental-sired cattle in the Cattleman's Beef Board Carcass Merit Project. The heritabilities (± SE) for WBSF, MS, HCW, FAT, and REA were 0. 34 ± 0.25, 0.43 ± 0.28, 0.73 ± 0.35, 0.16 ± 0.19, and 0.56 ± 0.31 in Angus; 0.43 ± 0.22, 0.30 ± 0.18, 0.21 ± 0.16, 0.35 ± 0.20, and 0.23 ± 0.16 in Charolais; 0.12 ± 0.11, 0.55 ± 0.22, 0.20 ± 0.14, 0.25 ± 0.15 and 0.34 ± 0.17 in Hereford; and 0.16 ± 0.14, 0.44 ± 0.20, 0.45 ± 0.20, 0.23 ± 0.16, and 0.30 ± 0.18 in Simmental. The genetic correlations, averaged across analysis type, for WBSF-MS, WBSF-HCW, WBSF-FAT, WBSF-REA, MS-HCW, MS-FAT, MS-REA, HCW-FAT, HCW-REA, and FAT-REA were -0. 17, 0.32, 0.30, 0.10, 0.39, 0.68, 0.77, 0.52, 0.66, 0.09, 0.08, 0.79, 0.50, and 0.55, 0.08, 0.62, 0.30, 0.61, 0.06, 0.65, 17, 0,32,23, 0,30, 0,10,17, 0,39,15, 0,86 pour les Angus,42, 0,77, 0,52,05,44,22,19, 0,66,24 pour les Charolais;43,04,33, 0,09, 0,08, 0,79,14,026, 0,38 pour les Hereford; et de 0,55, 0,08, 0,62,08, 0,30, 0,61,14, 0,06, 0,48 . The genetic correlation between WBSF and marbling score (MS) has been reported to be -0.31, (Koots et al. 1994b), -0.55 ± 0.22 (Wheeler et al. 1996), and -0.37 (Kim et al. 1998.The National Cattlemen's Beef Association coordinated a project in 1998 to study carcass merit in 13 breeds. The objectives included developing methodology and procedures for collection of information necessary for further development of expected progeny differences (EPD) for carcass merit traits, and to collect carcass data and measure tenderness of the longissimus lumborum by WBSF in contemporary groups of progeny of multiple sires within each breed. Genetic parameters estimated in this project are unique in the literature because of the large amount of field data that was collected under commercial conditions. Another objective was to determine if EPD for tenderness could be developed using these field data. The data used in this study represent the Angus-, Charolais-, Hereford-, and Simmental-sired 599 Abbreviations: EPD, expected progeny differences; FAT, 12-13th rib-fat; HCW, hot carcass weight; MS, marbling score; REA, ribeye area; WBSF, Warner-Bratzler shear force 4 Present address:

The objective was to determine the natural variability in beef fatty acid composition. We have used common gas chromatographic techniques to determine the fatty acid composition of phospholipids and triacylglycerols (TAGs) extracted from beef muscle (longissimus dorsi) from 800 sire-identified cattle originating from Iowa State University beef cattle breeding selection projects. Heritability of individual fatty acids and indexes of fatty acid desaturase and elongase systems were calculated by evaluating specific ratios of fatty acids (product/precursor). In general, we found that TAG composition is heritable, but phospholipid composition is not. The atherogenic index of TAGs as proposed by Ulbright and Southgate had a heritability estimate of 0.55 and 0.45 for the TAG and total lipids, respectively. Individual fatty acids of TAGs also had high heritability estimates. For example, the heritability estimates of 14:0 and 16:0 in TAG were 0.49 and 0.40, respectively. Monounsaturates 16:1 and 18:1 in TAGs both had heritability estimates greater than 0.5. Future research will focus on DNA sequencing of candidate genes from sires that are phenotypically divergent for a trait of interest. Ultimately, we plan to develop DNA markers for use in selecting breeding stock to improve healthfulness of fatty acids in beef.

and Implications The objective was to determine the natural variability in beef fatty acid composition and to identify single nucleotide polymorphisms (SNPs) in the stearoyl-CoA desaturase (SCD) gene to test the association of SNPs with fatty acid composition. We have used common gas chromatographic techniques to determine the fatty acid composition of phospholipids and triacylglycerols (TAGs) extracted from beef muscle (longissimus dorsi) from 800 sire-identified cattle originating from Iowa State University beef cattle breeding selection projects. Heritability of individual fatty acids and indexes of fatty acid desaturase and elongase systems were calculated by evaluating specific ratios of fatty acids (product/precursor). In general, we found that TAG composition is heritable, but phospholipid composition is not. The atherogenic index of TAGs as proposed by Ulbright and Southgate had a heritability estimate of 0.55 and 0.45 for the TAG and total lipids, respectively. Individual fatty acids of TAGs also had high heritability estimates. For example, the heritability estimates of 14:0 and 16:0 in TAG were 0.49 and 0.40, respectively. Monounsaturates 16:1 and 18:1 in TAGs both had heritability estimates greater than 0.5. Future research will focus on DNA sequencing of candidate genes from sires that are phenotypically divergent for a trait of interest. Ultimately, we plan to develop DNA markers for use in selecting breeding stock to improve healthfulness of fatty acids in beef. Three SNP candidates in the SCD gene were tested by using Iowa State University beef cattle. Two of the potential SNPs were homozygous in this population (n=123). We have classified 172 cattle into two genotypes, VA and VV, based on the third SNP. The ratio of palmitoleic acid (C16:1) concentration vs palmitic acid (C16:0) concentration of TAG is significantly associated with the SNP (P=0.02). There is no significant association of the SNP with the fatty acid composition of phospholipids.

IntroductionWe propose to improve the fatty acid composition of beef by capitalizing on the natural genetic differences among animals. It is our thought that improvements in the healthfulness of the fatty acid composition of beef can be made while maintaining other positive attributes. Stearoyl-CoA desaturase is responsible for the conversion of 16:0 and 18:0 to 16:1 and 18:1, respectively, the two major monounsaturated fatty acids of bovine lipids.