The Fatty Acid Composition of UK Organic and Conventional Milk

Summary

Bulk-tank milk was collected each month from organic (n=17) and conventional (n=19) dairy farms in the UK for a 12-month longitudinal study. All milk samples were analysed for fatty acid (FA) content. The effects of farming system type, herd production level and nutritional factors on the FA composition were investigated by use of mixed model analyses. Models were constructed for saturated fatty acids (SFA), the ratio of poly-unsaturated fatty acids (PUFA) to mono-unsaturated fatty acids (MUFA), total omega-3 FA, total omega-6 FA and conjugated linoleic acid (CLA). Organic milk had a higher proportion of PUFA to MUFA and of omega-3 FA than conventional milk, and contained a consistently lower omega-6:omega-3 FA ratio, considered to be beneficial, com-pared to conventional milk. There was no difference between organic and conventional milk with respect to the proportion of CLA. Other factors affecting milk FA content included month of year, herd average milk yield, breed type, use of a total mixed ration (TMR) and access to fresh grazing.