Effects of Forage and Grain-Based Finishing Diets on Fatty Acid Profile of Angus Steers Backgrounded Either in a Moderate Or in a High Plane of Nutrition

Abstract The objective of this study was to evaluate the fatty acid profile of beef backgrounded in two planes of nutrition and finished with forage-only or corn. Steers (n = 24) weighing approximately 298.63 ± 10.19 kg were randomly backgrounded in Triticale (100% DM; Moderate n = 12) and alfalfa (85% DM) and beardless wheat (15% DM; High, n = 12), blocked, and finished with forage-only (FORAGE – Alfalfa with 21% CP, 100% DM, n = 12) or with a grain-based diet (GRAIN - Alfalfa with 16% CP, 80% DM and Corn, 20% DM, n = 12). The feeding trial lasted 220 days (85 d backgrounding, 30 d finishing diet adaptation, and 105 d finishing). The fatty acid profile of strip loin steaks (m. longissimus lumborum) was assessed, and data were analyzed as a 2x2 factorial. Overall, no interaction effect between plane of nutrition and finishing diet was observed for individual or group of fatty acids. Minimal effects were observed for plane of nutrition. Steaks from steers backgrounded in Moderate had greater concentrations of C14:1T n-5 (P = 0.04) and C18:1TΔ n-9 (P = 0.04) when compared with steaks from steers backgrounded in High. Beef from steers finished with FORAGE showed higher concentrations of C10:0 (P = 0.01), C14:1T n-5 (P < 0.0001), C15:0 (P = 0.003), C16:0 (P = 0 .001), C16:1T n-7 (P < 0.0001), C17:0 (P = 0.001), C18:0 (P = 0.0002), C18:1TΔ n-9 (P = 0.0003), C18:2T n-6 (P = 0.005), C20:1 n-12 (P < 0.0001), C18:3 n-3 (P = 0.0003), 18:2 CLA t10c12 (P < 0.0001), C22:1 n-9 (P = 0.02), C22:2 n-6 (P = 0.001), and C22:5 n-3 (P = 0.02) when compared with beef from steers fed GRAIN. Beef fed GRAIN, had greater concentrations of C16:1 n-7 (P = 0.001), C18:1 n-9 (P = 0.004), C18:1Δ n-11 (P < 0.0001) and C18:2 n-6 (P = 0.02) when compared with beef fed FORAGE. Overall, backgrounding steers in moderate and high planes of nutrition does not affect the fatty acid profile of beef. Beef fed with FORAGE has higher total Omega 3 (P = 0.05), total Saturated (P < 0.0001), and total Trans fatty acids (P < 0.0001) when compared with beef fed GRAIN. GRAIN-fed beef has total Monounsaturated fatty acids (P = 0.0002) and higher Omega6:Omega3 (P = 0.0003). Regarding health indexes, based on its fatty acid profile, FORAGE-fed beef had Atherogenicity (P = 0.01) and Thrombogenicity indexes (P = 0.0001) when compared with beef fed GRAIN (Table 1).