Methane emission by goats consuming diets with different levels of condensed tannin-containing lespedeza and sorghum-sudangrass

G. Animut, R. Puchala, A.L. Goetsch, T. Sahlu, G. Detweiler, A. K. Patra, V. H. Varel, and J. Wells

Journal of Animal Science 84(Supplement 1):26. 2006

Twenty-four yearling Boer Spanish wethers (7/8 Boer; initial BW of 34.1 ñ 1.02) were used to determine effects of dietary levels of a condensed tannin (CT)-containing forage Kobe lespedeza (Lespedeza striata; K) and sorghum-sudangrass (Sorghum bicolor; G) on methane emission. Treatments were dietary K levels (DM basis) of 100, 67, 33, and 0% (100K, 67K, 33K, and 0K, respectively). Forages harvested daily were fed at 1.3 times the maintenance energy requirement. The experiment lasted 21 d, with measures on the last 8 d. N was 1.7 and 2.2%, in vitro true DM digestibility was 85.5 and 68.0%, and CT was 0 and 15.1% for G and K, respectively. DMI was similar among treatments (677, 664, 633, and 626 g/d; SE = 30.8) and gross energy (GE) digestibility increased linearly (P < 0.05) with decreasing K (47.1, 51.4, 58.9, and 65.6% for 100K, 67K, 33K, and 0K, respectively). ME intake increased linearly (P < 0.05; 398, 431, 485, and 513 kJ/kg BW0.75) and energy expenditure (356, 350, 399, and 504 kJ/kg BW0.75) and methane emission changed linearly and quadratically (P < 0.05) with decreasing K (10.9, 13.8, 17.6, and 26.2 l/d; 3.3, 4.0, 5.4, and 8.2% GE; 7.0, 7.7, 8.8, and 11.9% DE for 100K, 67K, 33K, and 0K, respectively). In vitro methane production by incubation of ruminal fluid for 3 wk with a medium for methanogenic bacteria and other conditions promoting activity by methanogens also was affected linearly and quadratically (P < 0.05) by K (7.0, 8.1, 9.2, and 16.1 ml for 100K, 67K, 33K, and 0K, respectively). The total bacterial count was similar among K levels, but the number of total protozoa increased linearly (P < 0.05) and changed quadratically (P < 0.07) as K declined (8.3, 11.8, 15.6, and 27.1 x 105/ml for 100K, 67K, 33K, and 0K, respectively). In conclusion, the CT-containing forage K decreased methane emission by goats regardless of nonzero level without deleterious effects on digestibility. The impact of K CT on methane emission appears attributable to changes in methanogenic bacterial activity, although alterations of protozoal actions might be involved as well.