Rendimiento y degradabilidad ruminal de materia seca y energía de diez pastos tropicales cosechados a cuatro edades Yield, and ruminal dry matter and energy degradability of ten tropical grasses harvested at four ages

The objective of the study was to determine dry mater yield (DMY), and in situ ruminal degradable dry matter and energy of ten grasses of the genera Brachiaria: B. brizantha (Insurgente), B. decumbens (Senal), B. humidicola (Chetumal), B. brizantha x B. ruzieziensis (Mulato I); Panicum: P. maximum cv. Mombasa, P. maximum cv. Guinea, P. maximum cv. Tanzania; and, Pennisetum: P. purpureum cv. Taiwan, P. purpureum cv. Cuban king grass, P. purpureum cv. Purple king grass, at 3, 6, 9 and 12 wk of regrowth, in three evaluation cycles. DMY for Pennisetum, Brachiaria and Panicum was: 3,037, 1,689 and 1,872 kg ha-1 (P<0.05). CP concentration decreased from 11.6 to 6.9 % (3 to 12 wk), without differences among genera. Concentration (%) of NDF, ADF and LIG were: 72.1, 43.5 and 8.1 (Brachiaria); 73.0, 45.8 and 9.0 (Panicum); and 68.8, 44.4 and 9.1 % (Pennisetum), values were 68.1, 40.1 and 8.2 (at 3 wk); and 76.2, 49.7 and 9.5 (at 12 wk). The in situ DM degradability was: 70.0 % (Brachiaria), 65.8 % (Panicum) and 72.9 % (Pennisetum) and decreased from 71.7 to 62.9 % (from 3 to 12 wk). Gross energy (GE) preincubation, was 3,802, 3,756, and 3,608 kcal kg-1 DM, for Brachiaria, Panicum, and Pennisetum, with no changes due to age of regrowth. In situ ruminal energy degradability (as % of incubated GE) was: 55.6, 51.4, and 57.9 % for Brachiaria, Panicum; and Pennisetum. In conclusion, age of regrowth and genus affected the nutritive value of the evaluated grasses.