Stubble height effects on limpograss pasture characteristics and performance of beef heifers

Limpograss (Hemarthria altissima [Poir.] Stapf. & C.E. Hubb.) is a C-4 species used in Florida beef production systems because of its cool-season growth, persistence on poorly drained soils, and high yield and digestibility. Animal performance on limpograss pastures, however, has been limited by low herbage crude protein (CP). This study evaluated the effect of canopy height of limpograss pastures and N supplementation of grazing cattle on sward characteristics and weight gain and blood urea N (BUN) concentration of yearling beef heifers. Under continuous stocking, six treatments were imposed that included all combinations of three stubble heights (20,40, and 60 cm) and two N-supplement levels (S, supplemented; NS, unsupplemented). During 1998 and 1999, treatments were replicated twice and arranged in a completely randomized design. Seasonal (84 d) daily gains from heifers grazing limpograss pastures were not different (p = 0.25) between the two years and averaged 522 g. For the intermediate stubble, 40-cm, there was no effect of supplementation on daily gains (P = 0.1), but daily gain increased 40 and 70% due to supplementation (P < 0.01) of heifers on pastures grazed to 20 and 60 cm, respectively. These data show that limpograss stubble height has an impact on pasture nutritive value affecting daily gains. Stubble height of approximately 40 cm seems to provide optimum gains of animals receiving no N supplement on continuously stocked pastures.