Copper, molybdenum and cobalt in herbage and ruminants from organic farms in Norway

Summary

To evaluate the animal nutritional status of copper, molybdenum and cobalt on Norwegian organic farms, soil, herbage and animal blood samples were collected from 27 dairy and sheep farms and analysed for Cu, Mo and Co. The herbage median (10th-90th percentile) Cu, Mo, and Co concentrations (mg/kg DM) and the Cu:Mo ratio in the first cut were 5.3 (3.9-6.8), 1.5 (0.6-4.8), <0.05 (<0.05-0.08) and 3.8 (1.1-8.3) and in the second cut 7.0 (5.7-9.3), 3.3 (1.6-10.1), 0.06 (<0.05-0.15) and 2.0 (0.8-5.2), respectively. The results of mixed model analyses of herbage Cu and Mo indicated that soil pH, soil organic matter content, herbage botanical composition, yield and phenological stage of timothy at harvest mostly influenced the herbage micronutrient concentration. We conclude that plant growth was not limited by the supply of Cu, Mo or Co, but the herbage mineral nutrient concentration alone was not balanced to meet the dietary needs of ruminants. Supplements of mineral nutrient mixtures and/or concentrates fortified with Cu and Co are required to ensure sufficient supply for ruminants.