Relationship between Chemical Composition and In Vitro Methane Production of High Andean Grasses.

The present study aims to establish the relationship between chemical composition and in vitro methane (CH) production of high Andean grasses. For this purpose, eight species were collected in dry and rainy seasons: , , , , , , and . They were chemically analyzed and incubated under an in vitro system. Species such as and were characterized by high crude protein (CP. 124 g/kg DM) and low neutral detergent fiber (NDF. 293 g/kg DM) contents in both seasons, contrary to grasses. This same pattern was obtained for , which presented the highest values of gas production, organic matter digestibility (DOM), metabolizable energy (ME) and CH production (241 mL/g DM, 59% DOM, 8.4 MJ ME/kg DM and 37.7 mL CH/g DM, on average). For most species, the content of CP, acid detergent fiber (FDA) and ME was higher in the rainy season than in the dry season, which was the opposite for CH production ( ≥ 0.05). In general, the nutritional content that most explained the behavior of CH production was the NDF content (R = 0.69). Grasses characterized by high NDF content produced less CH (R = -0.85).