Abstract
Purple prairie clover (PPC; Dalea purpurea Vent.),a native legume adapted to the North American prairie, is considered an excellent forage for ruminants and therefore is valuable for the remediation of native grass pastures. The objective of this study was to assess the impact of different levels of inclusion of PPC harvested at varying stages of maturity on the ruminal digestion of mixed native forage. Whole-crop PPC and native mixed grasses were harvested at vegetative (VEG), full-flower (FL) and seedpod (SP) stages of PPC. To assess maturity, PPC at each maturity was combined with mixed grasses at a ratio (DM basis) of 50:50. PPC harvested at FL was then combined with mixed grasses in ratios of 0:100, 25:75, 50:50, 75:25 and 100:0 to evaluate the effect of proportions of PPC on digestibility. Nylon bags containing respective substrates were incubated for 0, 2, 6, 12, 24, 48, 72 and 96 h in the rumen of three heifers to determine in situ degradabilities of DM, NDF and CP. Forages harvested at the VEG and FL stages had similar soluble (a) and potential degradable (b) fractions of DM and NDF, and both were greater (PFL>SP (P< 0.01). In contrast, effective degradability of NDF was similar between VEG and FL and both were greater (P< 0.05) than SP. Increasing PPC in the mixture linearly (Pa and b fractions of DM and NDF and the a fraction of CP. Effective degradabilities of DM, NDF and CP were linearly (P<0.001) and quadratically (P<0.001) increased with PPC, with the greatest effective degradability observed with ratios between 50:50 and 75:25. Efects of PPC on ruminal digestion depend on both the growth stage and its proportion in mixed legume-grass pastures.These results suggest that pastures that contain from 50–75% of PPC in full flower would have the highest nutritive value.