Scientists at the BBSRC strategically-funded Institute of Biological, Environmental and Rural Sciences (IBERS) at Aberystwyth University discovered that the molecules that give cut grass its distinctive 'green odour' kill off bacteria that convert healthy omega-3 fats into saturated fats in a cow's gut. IBERS receives strategic funding from the Biotechnology and Biological Sciences Research Council (BBSRC),
Dr Sharon Huws, Coleg Cymraeg lecturer in Animal Science at IBERS who led the research,said: "We've known for a while that milk contains a greater proportion of the healthy omega-3 fats in the summer than in the winter, and now we know it's probably down to the antimicrobial effects of the green odour products from grass.
"Obviously cows can't be outside all year round but we could, for example, supplement their winter feed with one or more of these products."
Approximately 4% of whole milk is made up of a mixture of different fats.
Too much saturated fat in the human diet can lead to health problems, including cardiovascular disease. But a proportion of the fats in milk are omega-3 fatty acids, which are generally considered good fats and are thought to have a number of health benefits.
The ratio of omega-3 to saturated fats in milk varies across the year and this research potentially answers why in winter, when cows are often housed inside and may not be eating fresh grass or silage, milk is less healthy overall.
Dr Huws added "Of course, it's not just milk that would be healthier with the supplemented feed, it would also be all the various products produced from whole milk - butter, cheese, yoghurts, milkshakes, and more."
This is good news in a world where the population is set to reach 9Bn by 2050 and the need for nutritious, affordable, accessible, and safe food has never been as important.
The research is ongoing with funding from the Welsh Government with links to industrial partners Waitrose, DairyCrest, Wynnstay and Volac.