The benefits of organic milk have been highlighted by a study showing milk from cows which graze outside on grass and clover contains more antioxidants and vitamins than that from conventional dairy farms.
An al fresco diet in cows results in milk with up to 60 per cent higher levels of conjugated linoleic acid (CLA9) which has been linked to a reduced risk of cancer, according to research from Newcastle University. The same study found 39 per cent more omega-3 fatty acid and 33 per cent more vitamin E, which are also thought to reduce the risk of cancer and cardiovascular disease. During the summer, when there is the most discrepancy between feeding techniques, the widest difference emerges between organic and non-organic milks.
Gillian Butler, the livestock production manager at Nafferton Ecological Farming Group, who led the research, said grazing provided around 84 per cent of food for cows on organic farms in the summer, compared to 37 per cent for conventionally farmed animals. The remaining diet of cows on non-organic farms comprised 29 per cent silage (preserved grass) and 34 per cent concentrate (a mixture including cereals and grains).
"We have known for some time that what cows are fed has a big influence on milk quality," Ms Butler said. "This research shows that on organic farms, letting cows graze naturally is the most important reason for the differences in compo-sition between organic and conventional milk."
She said that in the winter, cows in all dairy farms were fed in similar ways, so the discrepancy is reduced. Future research will focus on improving the nutritional composition of milk in winter, when cows are kept indoors and fed mainly on conserved forage.
Ms Butler added: "Switching to organic milk is a natural way to increase intake of nutritionally-desirable fatty acids, vitamins and antioxidants without increasing less desirable fatty acids and synthetic forms of vitamin E."