NUTRITIVE-VALUE OF CLIPPED MOTT ELEPHANTGRASS HERBAGE

Many tropical grasses are low in nutritive value, but 'Mott' dwarf ele phantgrass (Pennisetum purpureum Schumacher) has supported gains of ye arling cattle (Bos taurus) approaching 1 kg d(-1). To aid in identifyi ng optimum harvest management practices for Mott, this study quantifie d crude protein (CP) and in vitro digestible organic matter (IVDOM) co ncentrations of leaf blade, leaf sheath, stem, and total herbage harve sted following imposition of a wide range of clipping treatments. Trea tments in 1989 and 1990 included all 16 combinations of four defoliati on frequencies (3, 6, 9, and 12 wk) and four stubble heights (10, 22, 34, and 46 cm) in a randomized block design with three replicates. The soil was a hyperthermic, uncoated Aquic Quartzipsamment (Adamsville s eries). Data were analyzed by fitting multiple regression equations st arting with a second-order polynomial model. The range in IVDOM of tot al herbage harvested was from 653 to 791 g kg(-1) (1989) and 680 to 73 9 g kg(-1) (1990). Frequent defoliation to short stubble resulted in g reatest LVDOM; herbage harvested infrequently to short stubble was lea st digestible. Total herbage CP ranged from 87 to 140 g kg(-1) in 1989 and 89 to 133 g kg(-1) in 1990, and was greatest with frequent harves t to a tall stubble. Mott elephantgrass CP and IVDOM were high across a wide range of defoliation frequencies and stubble heights. Because o f Mott's high nutritive value even when defoliated infrequently (e.g., 9 wk), achieving yield and persistence goals can be the primary basis for selecting defoliation management practices.