Concentrations of micro-nutrients in forage legumes and grasses harvested at different sites

Forage is a major source of micronutrients for dairy cows. This study examined the concentrations of micronutrients in birdsfoot trefoil (Bf ), red clover (Rc), timothy (Ti) and meadow fescue (Mf ) at different sites, years and cutting dates. Mixtures of Bf+Ti, Rc+Ti and Rc+Mf were established at Skara (58°21'N; 13°08'E) and Umeå (63°45'N; 20°17'E) in Sweden. First-year leys (Umeå 2005, Skara 2005 and 2007) were cut on three occasions in spring relative to the maturity stage of timothy: one week before heading, at heading and one week after heading. Summer growth was cut six weeks after each of the three occasions in spring growth. The results show that there was a need for Cu supplementation in all treatments because of low Cu concentration. The relatively high Mo concentrations compared to the Cu concentration in both grasses at Skara, in Mf in second cut at Umeå, and in Bt in the second cut at Skara may further increase the demand for Cu supplementation in dairy cow rations because there is a risk that Cu can be bound to a sulphate-Mo-complex in the rumen. The Zn concentration was lower than required for dairy cows, except for the mixture with Ti and Rc in the second cut at Umeå. For Mn and Fe, concentration levels were appropriate for expected dairy cow requirements for all treatments.