Evaluation of cup -plant as a forage

In the dairy industry, production of stable quality and quantity of forage are important conditions. Thus, dairy producers have cultivated several excellent forage species to achieve these goals. Alfalfa (Medicago sativa L.) and corn (Zea mays L.) silage have been the most important forage sources in the north central USA, with their high yield and high quality. However, unfavorable environmental conditions such as wet soils or winter killing may reduce alfalfa production, and some erosion prone sites are not suitable for corn silage production. Cup-plant (Silphium perfoliatum L.) may be a promising alternative forage because of high productivity of highly digestible dry matter in environments unfavorable for conventional forages. This research addresses questions dealing with cup-plant as an alternative forage. In the first experiment, changes in dry matter (DM) and forage quality patterns with increasing maturity were investigated. Stems and leaves are the major plant fractions determining DM accumulation and forage quality. Stem cell wall material concentration increased most significantly with maturity; however, stem in vitro true digestibility (IVTD) did not decline below 530 g kg-1. A simple linear regression model for IVTD, based on node number without leaf (NWL) and growing degree unit (GDU) was: IVTD = 879 - 17.6 NWL - 0.11 GDU (r 2 = 0.87). In the second experiment, the effects of nitrogen (N), potassium (K), and phosphorus (P) fertilizer application on forage quality and factors associated with cup-plant fermentation were independently evaluated in the three experiments. Data from the three fertilization experiments showed that fertilization did not consistently affect forage quality but decreased buffering capacity at high levels. Fiber concentrations were negatively correlated to buffering capacity, but IVTD was positively correlated. In the third experiment, cup-plant silage was substituted for an alfalfa and corn silage mixture to evaluate the potential of cup-plant silage in lactating cow diets. Cup-plant silage can substitute for about 30% of an alfalfa and corn silage mixture in lactating cow diets without sacrifice of intake, milk composition, milk yield and digestibility. I conclude that cup-plant may partially substitute for traditional forages as a high quality silage crop in a dairy forage system.