Methane emission by goats consuming a condensed tannin-containing lespedeza, alfalfa , and sorghum-sudangrass

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

Journal of Animal Science 85(Supplement 1):290-291. 2007

Twenty-four yearling Boer Spanish (7/8 Boer; initial BW of 37.5 ñ 0.91) were used to assess effects of different condensed tannin (CT) sources on methane emission. Diets were Kobe lespedeza (Lespedeza striata; K), K plus quebracho providing CT at 5% DMI (Q), Sericea lespedeza (Lespedeza cuneata; S), and a 1:1 mixture of K and S (KS). Forages harvested daily were fed at 1.3 times the maintenance energy requirement. The experiment was 51 d divided in two phases. In phase 1 forage diets were fed alone, and in phase 2 25 g/d of polyethylene glycol (PEG) mixed with 50 g/d of ground corn was given. Adaptation periods were 28 and 7 d in phases 1 and 2, respectively. After adaptation, there were 6 d for feces and urine collections followed by 2 d for determining gas exchange. Ruminal fluid was collected at the end of the experiment via stomach tube for microbiology assays. N was 2.28 and 2.36%, in vitro true DM digestibility was 69.8 and 64.8%, and CT was 14.0 and 15.1% for S and K, respectively. DMI was similar among treatments (781, 714, 818, and 816 g/d for K, Q, S, and KS, respectively; SE = 43.0) and lower (P < 0.05) in phase 1 vs 2 (716 vs 849 g/d). Treatment and phase interacted (P < 0.05) in N digestibility (phase 1: 51.2, 47.8, 29.4, and 42.5%; phase 2: 66.4, 64.2, 62.5, and 65.1% (SE = 2.81) for K, Q, S, and KS, respectively). Energy digestibility was 45.9, 38.2, 37.3, and 41.6% for K, Q, S, and KS, respectively (SE = 2.08) and greater (P < 0.05) in phase 1 than 2 (42.9 vs 38.7%). Methane emission in phase 1 was 14.3, 11.7, 16.2, and 14.1 l/d for K, Q, S,and KS, respectively (SE =1.59), and in phase 2 PEG markedly increased (P < 0.05) methane emission (9.0 vs 19.1 l/d). In accordance, there was a substantial difference (P < 0.05) between phases in in vitro methane release by ruminal fluid incubated for 3 wk in a methanogenic medium and other conditions promoting activity by methanogens (11.5 and 22.9 ml in phases 1 and 2, respectively). Counts of total bacteria and protozoa were similar among treatments but considerably greater (P < 0.05) in phase 2 vs 1 (bacteria: 1.9 and 19.7 x 1011/ml; protozoa: 9.3 and 18.9 x 105/ml). In summary, CT from different sources had disparate influence on N digestion but similar effects on ruminal microbial methane emission by goats, possibly by altering activity of ruminal methanogenic bacteria though change in actions of other bacteria and(or) protozoa may also be involved.