How does feeding cows seaweed affect the nutritional properties of milk?

10 May 2021

By Eric Newton

With the rise in interest regarding the benefits of feeding seaweed to cows such as reducing methane emissions, the growth of aquaculture as a cultivator for marine biodiversity, and the potential for the carving out of a new industry that could support developing areas, one must ask – how does feeding cows seaweed affect the nutritional properties of milk?

In 2014, researchers at James Cook University, Australia, ran a panel of in vitro studies to see which species of marine and freshwater macroalgae, or seaweed, could have an effect on total gas production and methane if fed to cows. As methane is a greenhouse gas, it would be beneficial if this is reduced while also making use of a potential underutilized feed source. The authors found the species Asparagopsis, a red tropical seaweed, to reduce enteric methane emissions significantly, and this was followed by increased international in vivo work.

While this significant research was taking place, there has been an increased interest in the exploration of other types of seaweed, and the potential beneficial effects that this could have on animal health. Ascophyllum nodosum, a common brown seaweed found within the northern Atlantic Ocean has also been touted as having beneficial effects when fed to cows in small amounts, such as increasing their essential mineral status, providing a hepatoprotective effect, and reducing the shedding of E. coli.

If these aspects of aquacultural supplementation in cows are to remain true over a long period of practice, this could benefit not only dairy farmers in developed countries, but also to seaweed farmers in developing countries who will experience a surge in interest and investment. Along with economic advantages, there also could be public health benefits too – as seaweed is commonly a macromineral and trace element accumulator which when consumed by the cow, could result in mineral-enriched milk and dairy products. An example of this could be the translation of higher iodine in cow diets to higher iodine intakes of the consumer per unit of milk consumed. Given that iodine-deficiency is the second-most prevalent deficiency in the world, a potential benefit of iodine-enriched milk from seaweed supplemented cows could mean nutritional benefits for populations that are at-risk.

The question then becomes “How does seaweed supplementation of dairy cows specifically affect milk macromineral and trace element composition?” – and that is what researchers at the University of Reading (UoR) are aiming to find out, paying close attention to such important parameters as iodine and heavy metals, by working in collaboration with Matís, an Icelandic government owned, non-profit, independent research company.

With this research, UoR and Matis plan to provide insight as to how feeding seaweed to cows, to gain the positive benefits of such as previously reported in other studies, affects the nutritional quality of the milk.

For more information or to get involved please contact PhD student Eric E. Newton (Email: or supervisor Dr Sokratis Stergiadis (Email:

The author proposes additional reading if interested:

(Antaya et al, 2019) Production, milk iodine, and nutrient utilization in Jersey cows supplemented with the brown seaweed Ascophyllum nodosum (kelp meal) during the grazing season (

(Machado et al, 2014) Effects of Marine and Freshwater Macroalgae on In Vitro Total Gas and Methane Production (

(Rey-Crespo et al, 2014) The use of seaweed from the Galician coast as a mineral supplement in organic dairy cattle (