Chemical composition and methane emission of some tropical forage legumes from Indonesia

The objective of the present study was to investigate chemical composition and methane emission of some tropical forage legumes from Indonesia, namely Acacia mangium, Acacia villosa, Calliandra calothyrsus, Albizzia falcataria, Leucaena leucocephala, Leucaena diversifolia, and Sesbania grandiflora. These leaves were oven dried at 60°C, ground by a hammer mill (1 mm screen size), and subjected to chemical composition analyzes and in vitro incubation. Determination of chemical composition included crude protein (CP), ether extract (EE), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, and tannin. Samples (200 mg DM) were incubated in vitro with 10 ml of ruminal fluid and 20 ml of buffer solution at 39 °C for 24 h in four replicates. Parameters measured were total gas production, methane emission, volatile fatty acid (VFA) profiles, ammonia concentration, microbial population (total bacteria and total protozoa), and in vitro organic matter digestibility (IVOMD). Data were subjected to analysis of variance and Tukey’s test. Results showed that a number of forages contained CP of more than 30% DM, i.e. Acacia villosa, Leucaena leucocephala, Leucaena diversifolia, and Sesbania grandiflora. Exceptionally high tannin content was found in Acacia villosa in which the value was above 20% DM. The lowest total gas production was observed in the in vitro incubation of Acacia villosa, whereas the highest gas production was observed in that of Sesbania grandiflora. This pattern was also observed for the IVOMD parameter. The lowest and the highest methane emissions were observed in the incubation of Acacia villosa and Sesbania grandiflora, respectively.