Effects of an array of dietary treatments and length of feeding on ruminal methane emission and other variables in hair sheep

•Weight gain by hair sheep was greatest for a diet based on alfalfa with soybean oil.•Dietary lespedeza inclusion decreased digestion of organic matter and nitrogen.•Intake was greater for the diet based on lespedeza than alfalfa.•Ruminal methane was less with dietary lespedeza in the first but not second 12 wk.•Diets with lasalocid, coconut oil, or soybean oil had a similar effect on methane. Eighteen Katahdin sheep ewes (initial body weight [BW] = 73.7 ± 1.76 kg and age = 5.2 ± 0.56 yr) and 18 St. Croix ewes (54.7 ± 1.33 kg BW and 4.1 ± 0.42 yr) were used in an experiment to determine effects of dietary level of Sericea lespedeza (Lespedeza cuneata; 5.8% condensed tannins and 10.3 % crude protein, dry matter [DM] basis) and other supplemental ingredients on BW, feed intake, digestion, energy metabolism, ruminal methane emission, and levels of blood and ruminal fluid constituents. Diets were consumed ad libitum and included a concentrate supplement at approximately 0.45 % BW (DM). Alfalfa (Medicago sativa) was the basal forage for control (CON), ionophore (ION; lasalocid at 33 mg/kg DM), coconut oil (3%; CCO), and soybean oil (3%; SBO) diets, and forage in moderate- and high-lespedeza diets was a 1:1 mixture of alfalfa and lespedeza and all lespedeza, respectively (ALF:LES and LES, respectively). There were four 6-wk periods, with digestion assessed in wk 4 and measures with a respiration calorimetry system in wk 5. Although there was a three-way interaction involving dietary treatment, breed, and period, average forage intake was greater for LES than for CON, ION, CCO, SBO (P