2009 American Registry of Professional Animal Scientists. Beef steers were finished on ryegrass with corn or corn + corn oil supplementation in a 2-yr experiment to determine effects on performance and conjugated linoleic acid tissue concentration, especially cis-9, trans-11 (c9,t11). Rib steak (longissimus dorsi, LM) and subcutaneous fat (SQ) samples were analyzed for long-chain fatty acid concentrations. Angus and Angus crossbred steers (yr 1, n = 18, initial BW 369.4 29.1 kg; yr 2, n = 48; initial BW 364.1 1.07 kg) were backgrounded on rye pasture for 71 d (ADG 1.78 0.11 kg) and 41 d (ADG 1.24 0.77 kg), respectively, in yr 1 and yr 2. After rye grazing, steers were assigned to ryegrass pastures (cv. Big Daddy; yr 1: 4 pastures, 1.62 ha each; yr 2: 6 pastures, 1.46 ha each) for 83 d in yr 1 and 112 d in yr 2, and fed corn at 1% BW, without or with corn + corn oil (0.075% BW). In yr 1, steer initial BW (n = 16; 424.3 27.83 kg), 83-d ADG (1.78 vs. 1.89 kg), carcass weight (347.9 vs. 354.44 kg), and QG (12.27 vs. 12.61; 12 = US Select +) were similar for corn vs. corn + corn oil treatments. In yr 2, a ryegrass-only treatment was added to the corn and corn + corn oil treatments used in yr 1. Steers (n = 37, initial BW 390.1 kg 27.4) assigned to ryegrass only (n = 9), corn (n = 14), or corn + corn oil (n = 14) treatments had respective 112-d ADG of 1.07, 1.65, and 1.62 kg (P < 0.01); carcass weights of 288.1, 321.4, and 326.0 kg (P < 0.01), and QG of 9.78, 10.57, and 10.29 (10 = US Select, P > 0.28). Feeding corn + corn oil decreased supplement intake in yr 1 (P < 0.03), but it did not improve ADG above feeding corn at 1% BW in either year. In yr 1, concentrations of c9,t11 were similar for corn and corn + corn oil in LM, but corn + corn oil had higher (P < 0.04) concentrations in SQ samples. In yr 2, concentration of c9,t11 was highest for LM (P < 0.03) and SQ (P < 0.02) in corn + corn oil compared with similar values for the ryegrass-only and corn treatments. Results indicate that addition of corn oil with corn may increase conjugated linoleic acid in beef steers finished on ryegrass pasture, but may not affect performance or QG.
The Professional Animal Scientist