Nutrient composition, in vitro digestibility, and methane production of two tropical grasses: Effect of grazing frequency and plant spacing

This study aimed to evaluate the dry matter yield, nutrient composition, in vitro and methane produced from Megathyrsus maximus (Ntchisi) and Cenchrus purpureus grazed at two grazing frequency (3 and 6-week, (GF)) with two plant spacing (0.5 m x 1 m and 1 m x 1 m). The design of this experiment was split-split plot design in 2 x 2 x 2 factorial arrangement. Milled samples were analyzed for chemical composition, In vitro dry matter digestibility (IVDMD), total gas production, methane (CH 4 ) production, total volatile fatty acid content, content of acetate, butyrate, propionate and acetate: propionate ratio. The M. maximus grazed at 6-week GF with 1 m x 1 m spacing had the highest dry matter yield. The crude protein (CP) content of the grasses ranged from 104.24 – 181.35 g/kg DM with C. purpureus grazed at 3-week with 1 m x 1 m spacing ranked highest in CP content and protein fraction A, B 1 , and B 2 . Megathyrsus maximus at 6-week GF with 1 m x 1 m spacing produced the highest content of acid detergent fibre. Metabolizable energy (ME), short chain fatty acid and volume of gas produced at 48 h of incubation was highest for M. maximus grazed at 3-week GF with 0.5 m x 1 m spacing. Megathyrsus maximus at 3 and 6-week GF with 0.5 m x 1 m spacing displayed highest CH 4 value. Acetate, propionate, and total volatile fatty acid were significantly ( P <0.05) highest for M. maximus grazed at 6-week with 0.5 m x 1 m spacing.