Methane production and microbial protein synthesis in adult sheep fed total mixed ration as mash and as complete feed block

Sixteen rams in two groups were fed ad libitum total mixed ration as mash (TMRm) and as block (TMRb) for 90 days, and methane (CH4) emission was estimated by standard SF6 tracer technique. Feed samples were also incubated in vitro for calculating CH4 emission. In vitro incubation revealed lower (P < 0.05) gas production and CH4 from TMRb. Rams fed on TMRb consumed higher (P < 0.05) dry matter (DM), digestible crude protein (CP) and metabolizable energy (ME). The digestibility of nutrients was similar between the groups except for CP, which was higher in TMRb. The CH4 emission per unit digestible DM and organic matter intake was lower (P < 0.05) from TMRb, resulting in lower energy loss as percentage of dietary energy and higher ME intake as compared to TMRm. Microbial protein synthesis (MPS) as assessed from urinary purine derivatives was higher in TMRb. The rams on TMRb also exhibited improved N utilization compared to TMRm. Post-feeding (4 h) ruminal attributes in TMRm showed higher total N and lower acetic and butyric acid with an increased total ciliate protozoa and entodinia population. It may be concluded that TMR offered in block form emits less CH4 and saves ME, besides improving CP digestibility, MPS and N utilization.