|Wells, James - Jim|
Submitted to: Animal Feed Science And Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/2007
Publication Date: 7/15/2008
Citation: Animut, G., Puchala, R., Goetsch, A.L., Patra, A.K., Sahlu, T., Varel, V.H., Wells, J. 2008. Methane emission by goats consuming different sources of condensed tannins. Animal Feed Science and Technology 144:228-241. Interpretive Summary: Greenhouse gas production has become a serious environmental concern. After carbon dioxide, methane is the major greenhouse gas contributing to global warming. Cattle contribute approximately 73% of the methane produced by livestock, with sheep and goats accounting for roughly 20%. Methane production by ruminants also presents a 5 to 15% loss of feed energy. Thus, developing feeding strategies to minimize methane emission is desirable to mitigate emission of greenhouse gas and reduce feed costs. Forages containing condensed tannins have been shown to reduce methane emission, however, they also can reduce animal performance. Therefore, it is important to determine the species of forage to feed which will not only reduce methane emission, but maintain animal performance. Polyethylene glycol (PEG) is a detergent and has a high affinity to bind to condensed tannins. It was used in this study to attenuate the potential negative effects of condensed tannins on animal performance. This was shown to be true, as PEG increased dry matter intake and nitrogen digestibility. However, PEG negated some of the positive effects of the condensed tannins by significantly increasing the methane production when it was fed as opposed to not being fed.
Technical Abstract: Twenty-four yearling Boer x Spanish wethers (7/8 Boer; initial body weight [BW] of 37.5 plus/minus 0.91 kg) 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% of dry matter (DM) intake (KQ), 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 days divided into two phases. In phase 1 forage diets were fed alone, and in phase 2 25 g/day of polyethylene glycol (PEG) was given mixed with 50 d/day of ground corn. Adaptation periods were 28 and 7 days in phases 1 and 2, respectively. After adaptation there were 8 days for feces and urine collections with gas exchange also measured on the last 2 days. Ruminal fluid was collected at the end of the experiment via stomach tube for microbiology assays. The N concentration was 22.8 and 23.6 g/kg DM, in vitro true DM digestibility was 0.698 and 0.648, and the level of CT was 140 and 151 g/kg DM for S and K. respectively. DM intake was similar among treatments (776, 717, 806, and 800 g/day for K, KQ, S, and KS, respectively; SE = 51.7) and lower (P < 0.05) in phase 1 vs. 2 (699 vs. 851 g/day). Treatment and phase interacted (P < 0.05) in N digestibility (phase 1: 0.514, 0.491, 0.280, and 0.413; phase 2: 0.683, 0.650, 0.638, and 0.662 (SE = 0.0302) for K, KQ, S, and KS, respectively). Energy digestibility was 0.462, 0.390, 0.373, and 0.410 for K, KQ, S, and KS, respectively (SE = 0.0248), and was similar between phases (0.422 and 0.396 for phase 1 and 2, respectively; SE = 0.0147). Methane emission was 14.3, 11.7, 16.2, and 14.1 1/day for K, KQ, S, and KS, respectively (SE = 1.25), and in phase 2 PEG markedly increased (P < 0.05) methane emission (9.0 vs. 19.1 1/day). In accordance, there was a substantial difference (P < 0.05) between phases in in vitro methane release by ruminal fluid incubated for 3 weeks in a methanognic medium and with 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 10**11/ml; protozoa: 9.3 and 18.9 x 10**5/ml. In summary, CT from different sources had disparate influence on N digestion but similar effects on ruminal microbial methane emission by goats. However, in phase 2, when PEG was included in the diets, it significantly increased methane production.