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Title: How does frame size, forage type, and time-on-pasture alter forage-finished beef quality

item VOLPI-LAGRECA, GABRIELA - Clemson University
item Neel, James
item LEWIS, RON - University Of Nebraska
item SWECKER JR, WILLIAM - Virginia Tech
item DUCKETT, SUSAN - Clemson University

Submitted to: Journal of Animal Science and Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2018
Publication Date: 8/27/2018
Citation: Volpi-Lagreca, G., Neel, J.P., Lewis, R.M., Swecker Jr, W.S., Duckett, S.K. 2018. How does frame size, forage type, and time-on-pasture alter forage-finished beef quality. Journal of Animal Science and Research. 2(3): 1-7.

Interpretive Summary: Forage-finished beef is being promoted as healthier meat by many dieticians and medical professionals. Consequently, in recent years there has been an increased demand for forage-finished beef in the United States. Defining the factors that affect forage-finished beef quality remains an important challenge in the production of a consistent and consumer desirable product. In this three year study, we evaluated the effects of frame size, forage-type, and time-on-pasture on animal performance and carcass traits of pasture finished cattle, and their impact on the quality of beef produce. Results indicated that final body and carcass weights were greater for large frame animals. Longer time on pasture increased final body, carcass weight and carcass fat content, but did not change meat intra-muscular fat content. Meat tenderness was not impacted by any treatment. In pasture finishing systems, increasing time on pasture increases HCW and carcass fat, and decreases the n-6 to n-3 fatty acid ratio. However, frame size and forage-type appear to have only a minor impact.

Technical Abstract: Angus-cross steers (n = 144; 364 ± 37.7 kg BW; 13.5 mo.) were used in a 3-year study (2010-2012) to assess the effects of frame size, forage type and time-on-pasture (TOP) on animal performance, carcass traits and meat quality in pasture finishing systems. The treatments were defined by a 2x2x2 factorial arrangement, with frame size (Medium or Large), forage type (Pasture [PAST] or PAST + annual [ANN]) and TOP (151 or 205 d) as the main factors. Pasture consisted of a mix of bluegrass (Poa pratensis), orchardgrass (Dactylis glomerata), tall fescue (Festuca aurundinacea) and white clover (Trifolium repens), whereas ANN consisted of PAST + a high-sugar sorghum-sudangrass (Sorghum bicolor), with sorghum-sudangrass being grazed when available (generally all of August through mid-September). At 24 h postmortem, carcass traits were collected and a rib from each carcass was obtained for proximate composition, fatty acid profile, and Warner-Bratzler shear force (WBSF). Final BW and HCW were greater (P < 0.05) for Large compared to Medium frame steers. Longer TOP increased (P < 0.05) final BW, HCW, subcutaneous fat thickness, KPH, skeletal maturity, and total lipid content. However, marbling score was not affected (P > 0.05) by TOP. Steers of Medium frame had lower (P < 0.05) concentration of stearic (C18:0) acid and greater (P < 0.05) concentrations of palmitoleic (C16:1) acid and MUFA compared to Large. Forage type did not affect (P > 0.05) LM fatty acid composition. Longer TOP increased concentrations of palmitic (C16:0), palmitoleic (C16:1), and oleic (C18:1 cis-9) acids, and lowered concentration of stearic (C18:0) acid. Vaccenic (C18:1 trans-11) acid concentration was increased (P = 0.002) by increasing TOP. Concentrations of linoleic (C18:2 n-6) and arachidonic (C20:4 n-6) acids, and n-6 PUFA, and concentrations of eicosapentanoic (C20:5, EPA) and docosapentanoic (C22:5, DPA) acids, and n-3 PUFA were lower with longer TOP. The ratio n-6 to n-3 was lower (P > 0.05) with increased TOP. Despite skeletal maturity was increased (P < 0.0001) with longer TOP, WBS values remain similar as TOP increased. Warner-Bratzler shear force values were not affected (P > 0.05) by forage type or frame size either. Lower WBSF values were observed (P < 0.0001) as postmortem aging time increased. In pasture finishing systems, increasing TOP increases HCW, carcass fat and decreases n-6 to n-3 ratio. Frame size and forage type appear to have minor impact. Key words: Beef, forage, grazing