466 - Effects of Dietary Inclusion of Sericea Lespedeza Hay on Behavior, Heat Energy, and Ruminal Methane Emission by Growing Alpine Doelings and Katahdin Ewe Lambs

Twenty-four Alpine doelings (initial body weight (BW) and age of 25.3±0.55 kg and 10.4±0.11 mo, respectively) and 24 Katahdin ewe lambs (28.3±1.02 kg and 9.6±0.04 mo, respectively) were used to determine effects of dietary level of Sericea lespedeza (Lespedeza cuneata; 10% condensed tannins) on heat energy and ruminal emission of the greenhouse gas methane determined with an open-circuit calorimetry system. Pens with Calan feeding gates were used in the study with four 6–7-wk periods. Diets (i.e., treatments) consumed ad libitum were 75% ground hay, alfalfa, a 1:1 mixture of alfalfa and lespedeza (AL), and lespedeza. Data were analyzed with a 2 x 3 factorial arrangement of treatments, repeated measure of period, and a mixed effects model. Feeders were open 195 and 205 min/d for Alpine and Katahdin (SEM=9.8) and longer (P < 0.05) for diets with lespedeza (159, 209, and 231 min/d for alfalfa, AL, and lespedeza, respectively). Rate of dry matter intake (DMI) was greater (P < 0.05) for Katahdin vs. Alpine (10.2 and 6.1 g/min) and for alfalfa than for AL and lespedeza (11.1, 8.1, and 6.7 g/min, respectively). Heat energy was greater (P < 0.05) in MJ/d for Katahdin than for Alpine (10.19 vs. 7.90) and similar among diets (9.20, 9.40, and 8.53; SEM=0.266), but values in kJ/kg BW^0.75 were similar between animal types (560 and 579; SEM=8.4) and greatest (P < 0.05) among diets for AL (563, 592, and 553 for alfalfa, AL, and lespedeza, respectively). Ruminal methane emission differed (P < 0.05) between animal types in MJ/d (1.17 and 1.44), kJ/g DMI (1.39 and 1.23), and kJ/g average daily gain (ADG; 18.1 and 9.8 for Alpine and Katahdin, respectively). Regardless of period, diet did not impact methane emission in MJ/d or relative to DMI, BW, or ADG. In conclusion, it is unclear why dietary inclusion of lespedeza did not reduce ruminal methane emission as in previous studies. Species differences in methane relative to DMI and ADG (i.e., lower for sheep than for goats) deserve further attention.