Fish oil in feed boosts milk’s dietetic value

A doctoral research at the University of Helsinki has found that the nutritional quality of milk improves when fish oil or both fish oil and plant oil are added to the feed of lactating cows.

The study found adding oil to feed also has an impact on ruminal lipid metabolism­– changing the metabolism of fatty acids in the rumen, said the university in a press release, referring to the study.

Piia Kairenius from the Faculty of Agriculture and Forestry studied opportunities of altering the fatty acid composition of milk fat to improve human health.

Adding fish oil to the feed of lactating cows alone or together with plant oils increased the concentration of healthy polyunsaturated omega-3 fatty acids, such as EPA, DPA, and DHA in milk fat, among others.

This is based on an increase in the ruminal outflow of mono- and polyunsaturated fatty acids, which are beneficial to human health. As a result, their concentration in milk fat will also increase. At the same time, the synthesis of saturated fatty acids that have a negative impact on human health will decrease in the mammary gland.

However, fatty acids of fish and plant oil are modified in the bio-hydrogenation process in the rumen, increasing the proportion of long-chain trans-fatty acids transferred to milk fat. These trans-fatty acids may have a positive or negative impact on human health. Trans- fatty acids generated in industrial processes are known to increase the risk of cardiovascular diseases among the consumers.

“The nutritional impact of the intermediates of long-chain trans-fatty acids formed in ruminal lipid metabolism is not yet known, although some have even been found to have a positive impact,” said Kairenius.

According to Kairenius, it is important to understand the mechanisms that affect the composition of the milk fat of lactating cows and how the composition of milk fat can be altered by using, for example, different feeding strategies,.

“In developed countries dairy products are a significant source not only of high-quality proteins and other important nutrients for human beings but of fat, too. This study aims to examine the nutritional property of milk, dairy products and meat, to improve their quality and, therefore, to improve the health of consumers.”

Kairenius is scheduled to defend the doctoral dissertation entitled "Role of dietary fish oil and plant oil supplements in ruminal lipid metabolism and fish oil induced milk fat depression in lactating cows" on 13 November.