Scientists at Utah State University doubled CLA content in milk by feeding dairy herds calcium salts of palm and fish oil alone, and tripled it by adding extruded, full fat soybean oil to the feed as well.
The study, led by Dr Tilak Dhiman, has been published in this month's edition of the Journal of Dairy Science.
The study adds further evidence that cows' diets play an important role in the nutritional quality of dairy products made from their milk.
Some studies on animals have shown CLA to be effective in fighting and preventing certain cancers, while trials on both humans and animals have also shown CLA can help to reduce body fat in the long term.
The research team at Utah compared dairy cows on an ordinary basal diet containing 44 per cent forage and 56 per cent concentrate with those on a basal diet supplemented with various levels of fish oil and soybeans.
They found the best supplement combination for increasing CLA in both milk and cheese was cow feed containing 0.75 per cent soybean oil and 2.7 per cent fish oils.
Crucially for dairy firms, the scientists also found no significant change in taste to either the milk or the cheese after increasing CLA content. They used a team of trained sensory analysts to make sure.
One problem the study found was that there was a "slight tendency"for lower milk fat in the soybean oil group. "Dairy farmers are paid premium price for higher milk fat. Therefore, even a small decrease in milk fat could be of economic value to dairy producers."
The results, nevertheless, echo recently published research by Ireland's Teagasc food research centre. There, scientists doubled CLA content in cheese by feeding cows 100g of sunflower oil per day and leaving them to graze on grass.
Project leader Dr Catherine Stanton, from the biotechnology department at Teagasc, said the research was very important because it showed that CLA levels could be elevated significantly and that "you can do it through very simple management approaches".
Stanton told www.DairyReporter.com that CLA-enriched dairy products have great potential for producers in the current wave of consumer health trends.
"We have the information and the know-how, it's more a case of if the consumers are ready for it. You have to ask, do they know anything about it [CLA], and I think the answer to that at the moment is no."
She said CLA fatty acids could become the next 'omega-3' or 'probiotics' but it all depended on educating consumers.
One problem may be how to present CLA in both a way that consumers understand and so that it complies with unspoken functional food codes, especially in relation to CLA's suggested anti-cancer properties.
At a talk on functional dairy at the recent Drinktec expo, Dr Michael de Vrese, of Germany's Federal Research Centre for Nutrition and Food, said it was still generally forbidden to claim a product may directly prevent a particular disease, although risk reduction claims will be tolerated in the European Union.