Effect of grassland management in organic and conventional farming systems on bovine milk quality – a field study

Summary

Thirty-two dairy farms in Middle-Norway participated in a field study in 2007 and 2008. Nine organic farms with short-term grassland (SO) were paired with 9 conventional farms with short-term grassland (SC) and 7 organic farms with long-term grassland (LO) were paired with 7 conventional farms with long-term grassland (LC) with regard to proximity and calving pattern. Every second month feed and tanker milk samples were collected from each farm. Data from the Norwegian dairy herd recording system were collected and botanical composition before first cut in 2007 was analysed. Milk samples were analysed for chemical composition, fatty acid composition, vitamin concentration, selenium concentration and phytoestrogen concentration. In this paper results from 2007 are presented. Milk quality was more influenced by production system then grassland system. Higher proportions of SFA and lower proportion of oleic acid in milk from O compared to C may be a future challenge for adjusting feed ratios in organic farming in Norway. Red clover stands for the main botanical effect in this study with strong effect on equol concentrations. The potential health effects of equol should be investigated further.