Grazing characteristics in the dwarf napiergrass (Pennisetum purpureum Schumach) pasture by breeding beef cows at the first and second years after establishment in Kyushu

In order to determine grazing characteristics in the dwarf napiergrass pasture under the rotational grazing system, 5a of pasture established by rooted tillers of dwarf variety of late-heading type (DL) was grazed by 3 head of breeding beef cows in the following 2 years after establishment in 2001 and 2002. Rotational grazing was conducted at 4 and 5 times for about 1-week grazing with 3-weeks and 1-month rest period in 2001 and 2002, respectively. Tiller number increased seasonally from the first through to the fourth or fifth grazing, and herbage dry matter weight reached the peak at the fourth grazing both years, while some characters such as plant height, mean tiller dry matter weight and percentage leaf blade tended to decrease with the grazing. The relationships between pre-grazing tiller number and the increasing rate of tiller number at the following grazing in each row of plots were negatively correlated among 4-5 grazings both years. From the stratified clip method, pre-grazing percentage leaf blades were 100% in the first and second strata counted from the top of canopy and those in the third strata were nearly 95% and 80% in 2001 and 2002. respectively both years. Pre-grazing leaf blades in the top two and in the third strata were consumed perfectly and almost perfectly, respectively both years. Herbage consumption increased with the grazing up to the third and fourth grazing and dropped at the last grazing due to the poor regrowth under the decreasing air temperature both years. Dry matter intake per head averaged 4.3-10.8kgDM/head/day in 2001 and 6.7-11.4kgDM/head/day(15.5-28.6gDM kgLW day) in 2002. Grazing time on DL napiergrass was stable at 50-60% in daytime at the first grazing day both years, while that at the last grazing day tended to increase with the grazing bath years. Thus, live weights of 3 head of beef cows were maintained in the growing from the second to the fourth time without concentrate feeding in 2002, when dry matter intake was above 20gDM/kg LW/day.