281 Effects of feeding endophyte-infected tall fescue seed to Angus steers on ergovaline concentration, lipid oxidation, and skeletal metmyoglobin reductase activity

This study was aimed to determine the ergovaline concentration, lipid oxidation, and skeletal metmyoglobin reductase activity in Angus steers fed with endophyte-infected tall fescue seed. Animals were blocked into light (n = 4, 205.5 ± 7.4 kg), medium (n = 5, 231.3 ± 8.2 kg), and heavy (n = 3, 272.7 ± 8.4 kg) groups and randomly assigned to either a KY31 seed treatment (6796 ppb ergovaline; 20 µg/kg BW; E+; n = 6) or a KY32 control (< 100 ppb; E-; n = 6) by Calan® gates during a 70-d feeding period from June to August of 2015 (period 1), followed by a 150-d resting period and another 64-d feeding period from January to March of 2016 (period 2). In both periods, there was a 2-way treatment × time interaction for ergovaline concentration in blood (P = 0.002 and 0.022, respectively), with E+ steers having 0.59 to 0.95 nM more than E- steers on d 3 (P < 0.001). In period 1, TBARS values were greater in blood serum of E+ steers than in that of E- steers (6.56 vs. 2.56 µM MDA; P = 0.048) and an overall increase in MDA from d 0 (2.39 µM) to d 3 (7.59 µM) was also observed (P = 0.049). At slaughter, E+ steers had a blood TBARS value of 2.27 µM, greater than 1.15 µM in E- steers (P = 0.013). In postmortem muscle, the TBARS value was 0.68 and 0.77 µg/kg for E- and E+ steers, respectively (P = 0.239). There was no effect of endophyte-infected tall fescue seed on metmyoglobin reductase in longissimus thoracis (4.82 µM/min/g in E- muscle vs. 3.93 µM/min/g in E+ muscle; P = 0.484). Therefore, feeding endophyte-infected tall fescue seed increased ergovaline concentration and oxidative stress in the blood of Angus steers.