Abstract
Recent increases in livestock numbers in Mongolia have led to an increase in the risk of natural disaster. Grassland management by using scientific data is therefore becoming more important. Here, we estimated the forage intake of sheep to obtain basic information for calculating the carrying capacity of the Mongolian steppe zone. The study was conducted during September, 2012 and April, 2013 using 12 castrated sheep born in spring the previous year. Forage intake was calculated from fecal output, and digestibility was determined from the acid detergent lignin (ADL) contents of plants and feces. The dominant plants at the study site were typical steppe species such as Carex pediformis, Agropyron cristatum, and Stipa sp. The aboveground biomass on a dry matter (DM) basis was highest in September (1.080 t DM/ha) but decreased by 81.3% by February (P < 0.05). Body weight (BW), fecal output, ADL content, DM digestibility, and DM intake were statistically compared by month. BW (kg) differed significantly among seasons, but there was no difference among months (51.0 to 57.5). ADL content (% of DM) of plants was lower in September (6.28) and higher in February (10.85) and April (11.63). Fecal ADL content was lower in September (21.4) and higher in February (31.20) and April (31.80). Fecal ADL content increased linearly from September to April, but plant ADL content was the same in October and November. This difference likely occurred because the presence of snow on the ground surface led to differences between the plant parts ingested by sheep and the plant samples collected for chemical analysis and therefore differences in ADL content. DM digestibility (%) was 70.5 (September), 68.2 (October), 0.9 (November), 65.1 (February), and 63.2 (April). Daily DM intake (kg DM/day) was higher in October (1.73) and lower in April (1.30). Daily DM intake per kg BW did not differ significantly among seasons. Forage intake in winter and spring was higher than the current index for Mongolia. Moreover, the carrying capacity in winter and spring was lower than that in available reference data.
