Abstract
This study was conducted to determine an optimum grazing pressure on a temperate grass pasture in the southwest region of Japan. Each paddock was grazed seven times in each of six successive years under two levels of grazing pressure (high: H and low: L) per the amount of available standing crop. Annual total numbers of cattle grazed in H and L were 1368 and 1013 heads/ha and amounts of herbage dry matter (DM) consumed annually were 8174 and 7707kg/ha. The percentages of the amount of herbage consumed to the amount of standing crop were 47-86% in H and 36-62% in L. Herbage DM intakes per day per head (500kg of body weight) in H and L were 4.8-7.3kg and 6.5-9.8kg, respectively. In both treatments, those were high in spring and winter and were low in summer and autumn. The cover of tall fescue kept about 90% during this trial. The number of the grass species counted and the cover of all the grass species except tall fescue in H were a little higher than those in L. But, those in both treatments were almost stable after the second or third year of this trial. The concentration of several nutritive components in herbage differed with height of tall fescue, and the nutritive value was higher in short one. The quality of tall fescue was high in spring and decreased in summer, but it increased again in autumn and winter. Judging from the results described above, the percentages of herbage consumed to standing crop should be 60-70% in spring, 40% in summer, 50% in autumn and 70-80% in winter, though these values may change according to the fertilizer level or the number of rotation. These levels of grazing pressure are thought to be suitable for both animal performance and vegetation maintenance.
