Establishment of grazing dwarf napiergrass pasture for the laborsaving and environmentally conservative feeding system to breeding beef cows

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Objectives : Dwarf napiergrass (Pennisetum purpureum Schumach) of a late-heading type (dwarf-late, DL), introduced by the Dairy Promotion Organization, Thailand, has a high over-wintering ability and is the most suitable variety for grazing in southern Kyushu, Japan. DL napiergrass pasture can be oversown with Italian ryegrass (Lolium multiflorum Lam., IR) in early November to extend the grazing period in the next spring. The objectives of this study were firstly to examine the herbage mass, digestibility and crude protein (CP) content of DL and IR both before and after rotational grazing in relation to the daily live-weight (LW) gain of cattle 4 years after establishment in the lowlands of Kyushu, Japan and secondarily to examine the laborsaving vegetative propagation method of DL napiergrass in Okinawa prefecture.Materials and Methods : Four paddocks of DL pasture (5 a, 20m × 25m/paddock) were established by rooted tillers on May 6, 2002. The DL pasture was rotationally grazed by 3 b … More reeding cattle (Japanese-Black) for 3 cycles from August to December in 2002 and by 2-3 beef cattle for 6 cycles from June to December in 2003. Another 2 paddocks of DL pasture were established on May 5, 2004, and were rotationally grazed by 3 raising beef cows with other 4 paddocks for 4 cycles from June to October in both 2004 and 2005. Cattle LW was measured at 1100 h when cattle switched paddocks, and no concentrate or roughage was fed during this rotational grazing. Initial LWs were 451,359,276 and 276 kg/head in 2002, 2003, 2004 and 2005, respectively. In vitro dry matter digestibility (IVDMD) and CP content were measured in the herbage cut at 10cm above the ground surface at every cycle in 2004 for DL napiergrass and at 5cm in 2004 and 2005 for IR.Results : 1)Live-weight of grazing cattle on DL pasture increased at 0.43-0.56 kg/head/day in 2004 and 2005. 2)The carrying capacities on DL pasture were more than 1000 Cow-day/ha in 2002-2005. 3)Annual mean CP content and IVDMD for DL napiergrass were 81 g/kg DM and 0.641, respectively, in 2004 and IVDMD was higher than the average of tropical grasses (0.54). Annual CP contents for IR were 119 and 89 g/kg DM in 2004 and 2005, respectively and IVDMD, 0.805 and 0.738, respectively. Nursery plants of DL napiergrass can be obtained by the laborsaving vegetative method, where the over-wintered tillers were sampled at Okinawa prefecture in March 2006.In conclusions, this study demonstrates that DL pasture can be rotationally grazed by beef cows with higher quality of herbage than the average of tropical grasses, and the laborsaving vegetative method can be developed by transporting nursery tillers from Okinawa prefecture in spring. Less