Effects of Different Levels of Lespedeza and Supplementation with Monensin, Coconut Oil, Or Soybean Oil On Ruminal Methane Emission by Mature Boer Goat Wethers After Different Lengths of Feeding

Abstract

The effect of forage condensed tannins on ruminal emission of the greenhouse gas methane was compared with those of other rumen modifiers. Mature Boer goat wethers (36) consumed pelleted alfalfa hay (CON), Sericea lespedeza hay (HSL; 6.4% condensed tannins), a 1:1 mixture of alfalfa and lespedeza (MSL), or alfalfa with monensin (ION; 22 mg/kg), coconut oil (CCO; 4%), or soybean oil (SBO; 4%). Total dry matter intake in the 20-week study (3.86, 3.75, 3.52, 3.69, and 3.64% body weight) and total tract organic matter digestibility determined every 5 weeks (72.8, 69.5, 70.3, 72.0, and 71.1% for CON, MSL, HSL, ION, CCO, and SBO, respectively) were not affected by treatment. Ruminal methane emission was not influenced by period but was greatest among treatments for CON expressed as percentages of gross (10.3, 6.8, 6.3, 7.2, 6.5, and 6.5%) and digestible energy (14.8, 10.2, 9.3, 10.6, 9.8, and 10.1% for CON, MSL, HSL, ION, CCO, and SBO, respectively). In conclusion, a 1:1 mixture of alfalfa and lespedeza, with a low to moderate level of condensed tannins, had similar effect on ruminal methane emission as lespedeza as the sole forage (31 and 37% decreases relative to digestible energy intake, respectively). Inclusion in basal alfalfa diets of monensin and coconut and soybean oils elicited similar decreases in methane emission (28, 34, and 32%, respectively). There was no evidence of adaptation to any of the modifiers, with methane emission determined in weeks 5, 10, 15, and 20.