Methane production and energy partitioning in sheep fedAndropogon gayanusgrass ensiled at three regrowth stages

Abstract

Ribeiro Jr., G. A., Teixeira, A. M., Velasco, F. O., Faria Jr., W. G., Jayme, D. G., Maurício, R. M., Gonçalves, L. C. and McAllister, T. A. 2015. Methane production and energy partitioning in sheep fed Andropogon gayanus grass ensiled at three regrowth stages. Can. J. Anim. Sci. 95: 103–110. This study was undertaken to evaluate the effect of harvesting Andropogon gayanus at different regrowth stages (56, 84 and 112 d) on the nutritional value of silage and CH4emissions from sheep. Rams (n=18) were adapted to silages for 21 d after which intake and digestibility were measured over 5 d in a completely randomized design (six rams/treatment). Heat production and methane emissions from each ram were measured in a respiration chamber over 24 h. Silage dry matter (DM; 54.4 g kg−1BW0.75d−1) intake was not influenced (P>0.05) by silage regrowth stage, but apparent DM digestibility linearly decreased (P<0.05) from 526 to 380 g kg−1with increasing regrowth. Energy lost as a percent of gross energy intake (GEI) linearly increased with longer regrowth, yet no effect on CH4losses (as% GEI; g kg−1DM; g kg−1digestible DM) or heat production were observed. Ensiling A. gayanus grass at an earlier regrowth stage (56 d) will improve silage quality, but improvements in the energetic value are not due to a reduction in enteric CH4emissions as a% GEI.