BackgroundAs consumers continue to request food products that have health advantages, it will be important for the livestock industry to supply a product that meet these demands. One such nutrient is fatty acids, which have been implicated as playing a role in cardiovascular disease. Therefore, the objective of this study was to determine the extent to which molecular markers could account for variation in fatty acid composition of skeletal muscle and identify genomic regions that harbor genetic variation.ResultsSubsets of markers on the Illumina 54K bovine SNPchip were able to account for up to 57% of the variance observed in fatty acid composition. In addition, these markers could be used to calculate a direct genomic breeding values (DGV) for a given fatty acids with an accuracy (measured as simple correlations between DGV and phenotype) ranging from -0.06 to 0.57. Furthermore, 57 1-Mb regions were identified that were associated with at least one fatty acid with a posterior probability of inclusion greater than 0.90. 1-Mb regions on BTA19, BTA26 and BTA29, which harbored fatty acid synthase, Sterol-CoA desaturase and thyroid hormone responsive candidate genes, respectively, explained a high percentage of genetic variance in more than one fatty acid. It was also observed that the correlation between DGV for different fatty acids at a given 1-Mb window ranged from almost 1 to -1.ConclusionsFurther investigations are needed to identify the causal variants harbored within the identified 1-Mb windows. For the first time, Angus breeders have a tool whereby they could select for altered fatty acid composition. Furthermore, these reported results could improve our understanding of the biology of fatty acid metabolism and deposition.

Seventy-three crossbred steers (initial BW = 170.5 +/- 5.5 kg) from The Ohio State University (Exp. 1) and 216 crossbred steers (initial BW 135.4 +/- 4.4 kg) from the University of Illinois (Exp. 2) were used to determine the effect of source of energy and rate of growth on performance, carcass characteristics, and glucose and insulin profiles on early-weaned steers. Effects of the diets used in Exp. 1 and 2 on ruminal pH and VFA concentrations were quantified using ruminally fistulated steers (Exp. 3). Cattle were weaned at an average age of 119 d in all experiments and were allotted by age, BW, and breed to one of four diets: high-concentrate, fed ad libitum (ALCONC), high-concentrate fed to achieve a gain of either 1.2 kg/d (1.2CONC) or 0.8 kg/d (0.8CONC), or high-fiber, fed ad libitum (ALFIBER). At 218 d of age, all steers were placed on the ALCONC diet until slaughter. Steers were implanted with Compudose at the initiation of all experiments and with Revalor-S when they were estimated to be 100 d from slaughter. When steers in Exp. 1 averaged 181 and 279 d of age, serum samples were collected to determine glucose and insulin concentrations. Steers were slaughtered when a fat thickness of 1.27 cm was reached (Exp. 1) or after 273 d on feed (Exp. 2). In Exp. 1, days in the feedlot (P < 0.01) and age at slaughter (P < 0.01) were lowest for ALCONC and ALFIBER steers, and greatest for 0.8CONC steers. Overall, ADG was greatest for ALCONC and lowest for 0.8CONC steers; feed efficiency was lowest (P < 0.01) for ALFIBER steers. Final BW did not differ (P > 0.57) among treatments. At 181 and 218 d of age, serum insulin was increased (P < 0.10) and intramuscular fat percentage was greatest (P < 0.07), respectively, for ALCONC steers. In Exp. 2, overall ADG (P < 0.06) and final BW (P < 0.04) were greatest for ALCONC and lowest for 1.2CONC and 0.8CONC steers. Overall feed efficiency was greatest for 0.8CONC and lowest for ALFIBER (P < 0.01). Growing phase diet did not affect marbling score at 218 d of age or at slaughter (P > 0.81). In Exp. 3, differences in ruminal pH after feeding may have been a consequence of increasing acetate (ALFIBER), propionate (ALCONC), or a combination of VFA (0.8CONC and 1.2CONC), respectively (diet x time after feeding, P < 0.10). Controlling growth by limit-feeding a high-concentrate diet for only 100 d does not extend the growth curve of early-weaned steers or enhance intramuscular fat deposition at slaughter compared to ad libitum intake of a high-concentrate or high-fiber diet.

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The objective of this study was to determine the influence of beef LM nutrient components on beef palatability traits and evaluate the impact of USDA quality grade on beef palatability. Longissimus muscle samples from related Angus cattle (n = 1,737) were obtained and fabricated into steaks for trained sensory panel, Warner-Bratzler shear force (WBSF), lipid oxidation measured by thiobarbituric acid reactive substances (TBARS), fatty acid, and mineral composition analysis. Pearson phenotypic correlations were obtained by the correlation procedure of SAS. Beef palatability data were analyzed by the GLM procedure of SAS with USDA quality grade as the main effect. Specific mineral concentrations did not demonstrate strong correlations with WBSF or sensory traits (r = −0.14 to 0.16). However, minerals appeared to have a stronger relationship with flavor; all minerals evaluated except Ca and Mn were positively correlated (P < 0.05) with beef flavor. Stearic acid (C18:0), C18:2, C20:4, and PUFA were negatively correlated (P < 0.05) with all 3 panelist tenderness traits (r = −0.09 to −0.22) and were positively correlated (P < 0.05) with WBSF (r = 0.09 to 0.15). The MUFA were positively correlated (P < 0.05) with panelist tenderness ratings (r = 0.07 to 0.10) and negatively associated (P< 0.05) with WBSF (r = −0.11). The strongest correlations with juiciness were negative relationships (P < 0.05) with C18:2, C18:3, C20:4, and PUFA (r = −0.08 to −0.20). Correlations with beef flavor were weak, but the strongest was a positive relationship with MUFA (r = 0.13). Quality grade affected (P < 0.05) WBSF, TBARS, and all trained sensory panel traits, except livery/metallic flavor. As quality grade increased, steaks were more tender (P < 0.05), as evidenced by both WBSF and sensory panel tenderness ratings. Prime steaks were rated juiciest (P < 0.05) by panelists, whereas Select and Low Choice were similarly rated below Top Choice for sustained juiciness. Quality grade influenced (P < 0.05) beef flavor, but not in a linear fashion. Although there were significant correlations, these results indicate tenderness, juiciness, and flavor are not strongly influenced by individual nutrient components in beef LM. Furthermore, the positive linear relationships between USDA quality grade and beef palatability traits suggest quality grade is still one of the most valuable tools available to predict beef tenderness. ABSTRACT: The objective of this study was to determine the influence of beef LM nutrient components on beef palatability traits and evaluate the impact of USDA quality grade on beef palatability. Longissimus muscle samples from related Angus cattle (n = 1,737) were obtained and fabricated into steaks for trained sensory panel, Warner-Bratzler shear force (WBSF), lipid oxidation measured by thiobarbituric acid reactive substances (TBARS), fatty acid, and mineral composition analysis. Pearson phenotypic correlations were obtained by the correlation procedure of SAS. Beef palatability data were analyzed by the GLM procedure...

The objective of the present review is to discuss the results of published studies that show how nutrition affects the expression of genes involved in lipid metabolism and how diet manipulation might change marbling and composition of fat in beef. Several key points in the synthesis of fat in cattle take place at the molecular level, and the association of nutritional factors with the modulation of this metabolism is one of the recent targets of nutrigenomic research. Within this context, special attention has been paid to the study of nuclear receptors associated with fatty acid metabolism. Among the transcription factors involved in lipid metabolism, the peroxisome proliferator-activated receptors (PPARs) and sterol regulatory element-binding proteins (SREBPs) stand out. The mRNA synthesis of these transcription factors is regulated by nutrients, and their metabolic action might be potentiated by diet components and change lipogenesis in muscle. Among the options for dietary manipulation with the objective to modulate lipogenesis, the use of different sources of polyunsaturated fatty acids, starch concentrations, forage ratios and vitamins stand out. Therefore, special care must be exercised in feedlot feed management, mainly when the goal is to produce high marbling beef.