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We examined an intensive rotational grazing system for dwarf and late‐heading (DL) napiergrass (Pennisetum purpureum Schumach) pasture in a summer period, and an oversown Italian ryegrass (IR) pasture in a winter period for the 2 years following establishment. Four 0.05‐ha paddocks of DL napiergrass pasture (20 m ×  25 m) were established on 6 May 2002. They were rotationally grazed for 1 week, followed by a 3‐week rest period by 2–3 breeding or raising beef cattle (Japanese‐Black) for three and six cycles in a summer period during the first and second years of establishment, respectively. In the IR pasture, which was established by oversowing IR in both years, rotational grazing by 3–4 animals was conducted in March and April for two cycles of grazing for 1–2 days in each paddock in 2003 and for 3–5 days in all four paddocks in 2004. In the DL napiergrass pasture before grazing, the plant height, leaf area index and the ratio of leaf blade to stem were highest in the hot summer season, while tiller number increased and herbage mass tended to increase as grazing occurred, except for the first grazing cycle both years, and for one paddock in the second year. Herbage consumption, rate of herbage consumption and dry matter intake tended to decrease in three paddocks from the first to the third cycle in the first year, while herbage consumption and rate of herbage consumption tended to increase as grazing occurred in the second year. Dry matter intake averaged 10.2–14.5 and 15.4–23.2 g DM kg−1 liveweight (LW) day−1 over the four paddocks in the first and second year, respectively, and average daily gains were 0.09 and 0.35 kg head−1 day−1 in the first and second year, respectively. In the oversown IR pasture, herbage consumption tended to increase as grazing occurred, and the average daily gains were 1.49 and 1.36 kg head−1 day−1 in 2003 and 2004, respectively, except for the LW decrease during the first cycle in early March 2004. The carrying capacities on DL napiergrass pasture and IR pasture were estimated at 1016 and 208 cow‐days (CD) ha−1, respectively (annual total 1224 CD ha−1) in the first year and at 1355 and 207 CD ha−1, respectively (annual total 1562 CD ha−1) in the second year. Thus, DL napiergrass pasture oversown with IR can expand the grazing period for beef cows to late November, March and April, in addition to the summer season for the 2 years following establishment.

Napiergrass (Pennisetum purpureum Schumach), a C 4 tropical species, has been used for forage since it has high dry matter productivity, sustainability over several years in low-altitudinal sites of Kyushu, and little damage from serious pests. Recently, this grass has gained attention due to its potential as a bioethanol feedstock and for phytoremediation. Napiergrass cultivar Wruk Wona was grown as an annual crop in cadmium-(Cd-) contaminated soils under two cutting frequencies. Annual dry matter yield was not affected significantly by cutting frequency, but the concentration and uptake of Cd were higher when cut twice rather than only once, due to high Cd content of the herbage from the second cutting. Therefore, the soil Cd concentration was reduced by 4.6% when managed by cutting twice in a single year of Napiergrass cultivation.

Dry matter production and in vitro dry matter digestibility (IVDMD) of tillers in napiergrass (Pennisetum purpureum Schumach) were compared in twice‐cut field‐grown plants among three varieties with variable plant types, that is, Wruk wona of the tiller weight type, Taiwan A146 of the tiller number type and Merkeron of the intermediate type. The effect of the late July and the early September first cutting dates was also compared. Changes in the length and dry matter weight (DMW) of each tiller were investigated every month with some canopy structural characteristics and the IVDMD of the leaf blade (LB) and stem with leaf sheath (ST) of the harvested sample were determined at both the first cutting and the second cutting in early November. Annual total of herbage dry matter yield (HDMY) and in vitro digestible dry matter yield were the highest in Wruk wona, followed by Taiwan A146 and Merkeron in both cutting dates and the effect of the first cutting date on HDMY was dependent on plant type. The first cutting for the tiller weight type of Wruk wona should be favorable in early September due to the highest first‐cut HDMY, derived from the vigorous growth in each tiller. For the tiller number type of Taiwan A146, cutting was favorable in late July, due to the highest second‐cut HDMY by the largest number of regrown tiller. The DM production at the first and second cuttings positively correlated with leaf area development, mediated by the emerged individual leaf area on the tillers at the first cutting and by the tiller number on which several leaves attached at the second cutting. The IVDMD tended to be negatively related with DMW in both LB and ST of each tiller in each variety and this tendency reduced the varietal difference in IVDDMY, compared with that in HDMY.