Identification and quantification of n-alkanes in three tropical grasses

The main goal of this paper was to quantify the profile of n-alkanes in three tropical grasses. Hand plucking samples to simulate grazing were taking from Brachiaria brizantha cv. Marandu, Panicum maximum cv. Mombaca and Pennisetum purpureum cv. Cameroon. These samples were collected from an experiment established to assess intensive beef production from grasses throughout the year, under rotational grazing. Rotation order through the paddocks remained constant, with 30 days of rest after each grazing bout (16 paddocks, 2 days of grazing). Profiles of n-alkanes were analysed in three separate periods of the year: in the middle of the dry season (August 98; PERIOD 1), at the beginning of the wet season (November 97; PERIOD 2) and at the end of the wet season (April 98; PERIOD 3). Chain length was measured from C-27 to C-35. The concentration of odd n-alkanes, mainly C-35, C-33, C-31 and C-29, showed a wide variation between species and some variation between sampling periods. The most frequent alkanes in the Cameroon cultivar were C-33, C-31 and C-29, and in the cv. Marandu and Mombaca were C-33 and C-31.