Grazing behavior of sheep at different stocking rates in the Inner Mongolian steppe, China

Abstract

In free-ranging or grazing animals, physical activity can account for a substantial proportion of their total energy requirement with considerable consequences for animals at low production level. This study evaluated the effect of grazing intensity (GI) on behavior and walking distance of sheep grazing the Inner Mongolian steppe, China. In July 2008, 70 female fat-tailed breed sheep were randomly assigned to one of six GI plots, which were used according to the following herbage allowance (HA) classes: >12, 6–12, 4.5–6, 3–4.5, 1.5–3, and <1.5 kg dry matter kg −1 live weight corresponding to very light (GI 1), light (GI 2), light-moderate (GI 3), moderate (GI 4), heavy (GI 5), and very heavy (GI 6) grazing. The sheep were continuously on the plots throughout the grazing season until September 2008. Behavior of two sheep per plot was monitored by visual observation during daylight on two days in the beginning of each month. Walking distance was measured by global positioning system recorders between 12:00 h and 24:00 h. Organic matter (OM) intake was estimated in six sheep per plot using titanium dioxide as external fecal marker as well as the diet OM digestibility derived from fecal crude protein concentration. Two main grazing periods were observed at all GIs with afternoon grazing being longer than morning grazing. GI had no effect on the animals’ ruminating time and walking distance. However, with increasing GI sheep spent more time grazing and less time resting during daylight. Similarly, the animals tended to decrease their resting time in order to maintain their grazing time when daylight became shorter with advancing vegetation period. Thereby, they succeeded in maintaining their OM intake as GI increased from GI 1 to GI 5 despite lower HAs at high GIs. Nevertheless, OM intake was lower in GI 6 than in GI 2 and GI 3 sheep. Therefore, both, reduced feed intake and higher energy requirements for activity, will outweigh the expected profit from highly intensive grazing.