|Wells, James - Jim|
Submitted to: Animal Feed Science And Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2007
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 diets with different levels of condensed tannins from lespedeza. Animal Feed Science and Technology 144:212-227. Interpretive Summary: Greenhouse gas production is 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 represents 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, different levels of a specific forage containing condensed tannins have not been conducted. In this study with goats, four levels of a forage containing condensed tannins were fed. Methane production was reduced up to 50% both in the animal and in in vitro ruminal fluid studies when the highest level of the condensed tannins was fed. This reduction of methane production was attributed to the condensed tannins in the forage, which are thought to impact the activity of the protozoa and the methanogenic bacteria in the rumen of these animals.
Technical Abstract: Twenty-four yearling Boer x Spanish wethers (7/8 Boer; initial body weight [BW] of 34.1 plus/minus 1.02 kg) were used to determine effects on methane emission of dietary levels of a condensed tannin (CT)-containing forage, Kobe lespedeza (Lespedeza striata; K), and a forage very low in CT, sorghum-sudangrass (Sorghum bicolor; G). Treatments were dietary K levels (dry matter [DM] basis) of 100, 67.33, and 0% (100K, 67K, 33K, and OK, respectively). Forages were harvested daily and fed at approximately 1.3 times the maintenance energy requirement The experiment lasted 21 days, with most measures on the last 8 days. The CT concentration was 0.3 and 151 g/kg DM in G and K, respectively. DM intake was similar among treatments (682, 675, 654, and 648 g/day SE = 30.0) and gross energy (GE) digestibility increased linearly (P < 0.05) with decreasing K (0.472, 0.522, 0.606, and 0.666 for 100K, 67K, 33K, and 0K, respectively). Metabolizable energy intake tended to increase linearly (P < 0.09; 399, 406, 444, and 447 kJ/kg BW 0.75), whereas methane emission changed linearly and quadratically (P < 0.05) with decreasing K (10.9, 13.8, 17.6, and 26.2 1/day; 32, 42.57, and 88 kJ/MJ GE; 69, 81, 94, and 133 kJ/MJ digestible energy for 100K, 67K, 33K, and 0K, respectively). In vitro methane production by incubation of ruminal fluid for 3 weeks with a medium for methanogenic bacteria and other conditions promoting activity by methanogens also was affected linearly and quadratically (P < 0.05) by K level (7.0, 8.1, 9.2, and 16.1 ml for 100K, 67K, 33K, and 0K, respectively). The total bacterial count of ruminal samples was similar among K levels, but the number of total protozoa increased linearly (P < 0.05) as K declined (8.3, 11.8, 15.6, and 27.1 x 10**5/ml for 100K, 67K, 33K, and 0K, respectively). In conclusion, the CT-containing forage K decreased methane emission by goats regardless of nonzero level, although the effect per unit of K increased with decreasing K. Forage type (i.e., legume vs. grass) may have contributed to the effect of K on CH**4 emission, but most change appeared attributable to CT. CT may have directly impacted activity of methanogenic bacteria and alterations of protozoal activity could have been involved as well.