RESPIROMETRY AND METHANE EMISSIONS BY SHEEP FED ELEPHANTGRASS AT DIFFERENT CUTTING AGES

The aim of this work was to determinate the respirometry and enteric methane emission from sheep fed fresh elephant grass cut at 56, 84 and 112 days of regrowth. Eighteen crossbred sheep (34.7 +/- 6 kg) individually housed in metabolic crates were used in this experiment. The gases measurements were accomplished with an open circuit respirometric chamber. The experimental design was completely randomized with three treatments (grass regowth age) and six repetitions (sheep). The data were subjected to ANOVA and means were compared by SNK test (P < 0.05). The animals fed with elephant grass harvested at 56 days of regrowth had higher oxygen uptake and carbon dioxide and methane emissions. Heat production ranged from 87.19 to 143.57 Kcal/kg 0.75/day. The respiratory quotients were similar (P > 0.05) among treatments, averaging 0.98. Methane emissions ranged from 11.74 to 22.51 g/day. When expressed in g/kg 0.75/day, methane emissions were higher for sheep fed fresh elephant grass with 56 days of regrowth (1.53 g/kg 0.75/day). Methane emissions expressed in g/kg of dry matter (DM) intake or neutral detergent fiber (NDF) intake were higher (P < 0.05) for the grass harvested with 56 days of regrowth compared to the grass harvested in more advanced stage of maturity (112 days). However, methane emissions in g/kg of digestible DM (27.2 g/kg) and digestible NDF (44.4 g/kg) were similar among treatments. While daily methane emissions (g/kg 0.75/day) were higher in sheep fed fresh elephant grass harvested with 56 days of regrowth, it was not affected by regrowth age when expressed as g/kg of digestible DM or digestible NDF.