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 4 ) production of high Andean grasses. For this purpose, eight species were collected in dry and rainy seasons: Alchemilla pinnata , Distichia muscoides , Carex ecuadorica , Hipochoeris taraxacoides , Mulhenbergia fastigiata , Mulhenbergia peruviana , Stipa brachiphylla and Stipa mucronata . They were chemically analyzed and incubated under an in vitro system. Species such as A. pinnata and H. taraxacoides 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 Stipa grasses. This same pattern was obtained for H. taraxacoides , which presented the highest values of gas production, organic matter digestibility (DOM), metabolizable energy (ME) and CH 4 production (241 mL/g DM, 59% DOM, 8.4 MJ ME/kg DM and 37.7 mL CH 4 /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 4 production ( p ≥ 0.05). In general, the nutritional content that most explained the behavior of CH 4 production was the NDF content (R 2 = 0.69). Grasses characterized by high NDF content produced less CH 4 (R = -0.85).