Submitted to: Grass and Forage Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/18/2011
Publication Date: 4/19/2011
Citation: Pirhofer-Walzl, K., Soegaard, K., Hogh-Jensen, H., Eriksen, J., Sanderson, M.A., Rasmussen, J., Rasmussen, J. 2011. Forage herbs improve mineral composition of grassland herbage. Grass and Forage Science. 66(3):415-423. Interpretive Summary: It is a challenge to manage the mineral supply for ruminants that feed on grass-clover mixtures because the mineral content (e.g., calcium, phosphorus, potassium, magnesium) varies with plant species, organs and grassland management. We hypothesized that broadleaf herb species such as chicory, plantain, and burnet, mixed in a temporary intensive grass-clover mixture can improve the mineral composition of the total forage as well as lower the dependency of farmers on mineral supplementation. Mineral concentrations of several herbs, grasses, and legumes grown in mixtures were measured during two years. The concentrations of minerals in harvested forage were generally greatest in herb species, followed by legumes, and least in grasses. All of the plant species, however, had sufficient levels of minerals to meet the daily requirements of a lactating dairy cow. We concluded that including herbs in a forage mixture can improve and stabilize the mineral composition of the forage throughout the growing season and reduce the need for mineral supplementation of cattle.
Technical Abstract: Studies on plant mineral concentrations provided evidence of differences in mineral composition in plants species and their role in mineral supply to ruminants. We determined temporal differences in macro- and micromineral concentrations of grasses, legumes and herbs grown in a multi-species grassland and tested the effect of slurry application on mineral concentrations. We hypothesized that I) herbs have greater mineral concentrations than legumes and grasses grown in a multi-species mixture and II) slurry application dilutes mineral concentrations because of increased plant growth. Our results showed that differences in mineral concentrations among functional groups grown in a multi-species mixture can be used as a management tool to optimize the mineral content and mineral ratios of ruminant forage. Herbs generally had greater concentrations of all minerals, except N, than grasses and legumes. An increase of some minerals in herbs, but not in legumes from the first to the third cut suggests a complementary mineral contribution of legumes and herbs during the growing season. Slurry application had a weak effect on S and Zn concentrations. Nutrient requirement values of a Holstein dairy cow producing 35 kg of milk per day were met for K, Mg, Ca, Mn and Fe, but can be improved by changing botanical management.