Determinants of forage quality in Pensacola bahiagrass and Mott elephantgrass.

Abstract

Our objective was to determine animal responses and forage characteristics that could explain the greater forage quality of 'Mott' dwarf elephantgrass (Pennisetum purpureum Schum.) than that of 'Pensacola' bahiagrass (Paspalum notatum Flugge). Both grasses were harvested after 5 wk of regrowth in June and September. Sheep fed Mott hays had greater (P = .001) voluntary intake of digestible OM (DOM) than did those fed Pensacola, but voluntary intake of ash-free NDF (NDFa) did not differ (P = .21) between grasses. When hays were fed at equal NDFa intakes, sheep fed Mott chewed at a greater (P = .002) rate during eating, spent less (P = .028) time ruminating per unit OM intake, and had smaller (P = .006) prefeeding digesta pools of total and indigestible NDFa. Mott hays had greater N and K and smaller NDFa concentrations. Mott had greater (P = .001) epidermis and smaller (P = .001) sclerenchyma proportions in leaf blades, and leaf epidermis of Mott was more digestible (P = .011) in vitro. For both grasses, hays harvested in June had greater (P = .011) voluntary intake of DOM and shorter (P = .082) mean retention time of small ruminal digesta particles (< 1.18 mm) than did those harvested in September. Within grasses, there were no seasonal differences in NDFa concentration in hay, or in leaf anatomy. A less fibrous leaf structure and a more readily digested leaf epidermis may have accounted for the greater DOM intake of Mott than of Pensacola, but the greater DOM intake of hays harvested in June than of those harvested in September was not explained by measured forage characteristics.