The project was carried out in phases, with the first phase being a literature search for suitable seaweed species. Wageningen Livestock Research examined the chemical composition of eleven seaweeds and tested them for their capacity to reduce methane formation in cattle. These results were sufficiently positive to proceed to a cow feeding experiment. The practical experiment was carried out on the Dairy Campus in Leeuwarden. Three types of seaweed were used during ten weeks, namely: (1) Chondrus crispus, (2) Saccharina latissima and (3) 50/50 Fucus serratus + Saccharina latissima. The seaweed was added to the feed in small doses. The methane production was then measured for each seaweed species. In addition to methane production, the amount of feed intake, animal health and milk production were also monitored.

The laboratory study showed a significant decrease in methane in a number of seaweed species (5-10%). However, this result could not be reproduced in the field study. This did not show a reduction in methane emissions, but there may be an increase in milk production.

The study showed that the feed intake of the seaweed treatments was equal to the feed intake of the control group without seaweed. In addition, it has been found that one seaweed treatment led to a significantly higher milk production (in number of kilograms). This is strongly related to a significantly higher lactose content (in grams per day) in this milk. The fat and protein contents of the milk in all seaweed treatments remained unchanged and were equal to the control. None of the seaweed treatments had an effect on enteric methane emissions from the rumen through the mouth and nose of the cow. A possible explanation is that the dose may have been too low to measure a noticeable effect.