“Cultivation of seaweed is on the increase in Norway; while seaweed products are primarily aimed at the human food sector, expanding into animal feed could increase profitability,” Professor Margareth Øverland from the Norwegian University of Life Sciences (NMBU) and director of Foods of Norway, told us.
She and her team have been researching bioactive compounds from brown seaweed, particularly sugar kelp (Saccharina latissima), as well as the whole biomass, in animal diets.
The sugar kelp used in the studies was supplied by Seaweed Solutions, a company based in Frøya, near Trondheim, Norway.
Bioactive compounds
Her team has been evaluating two key bioactive compounds—fucoidan and laminarin—which have health benefits such as immune support, antiviral, antibacterial, and antioxidant effects.
"Laminarin, a type of beta-glucan, has a unique structure that stimulates the immune system, activating immune responses. Fucoidan, on the other hand, is a more complex polysaccharide and functions more like a prebiotic. It not only supports immunity but also positively impacts the gut microbiome," explained Øverland.
Salmon trials
To prepare seaweed for use in salmon and broiler chicken feed, the team processed it to reduce ash and water content, and subsequently extracted the bioactive compounds using techniques like hydrolysis and ultrafiltration. These extracts were then chemically characterized and evaluated for their immune-boosting properties using immune cells from salmon.
“We conducted three major studies with salmon. In one study, in freshwater, the fish were fed a diet containing varying levels of fucoidan for about five weeks. The inclusion levels were in insignificant amounts—just grams—because finding the correct dosage is crucial. If the dosage is too high, it can have the opposite effect of what we intend. Other fish were given a control diet for comparison.
“Afterwards, we performed an in vitro test by extracting immune cells from the salmon's head kidney and exposing them to the pathogen Aeromonas salmonicida (As) to observe the immune response. The results indicated that fucoidan fractions might help regulate immune function. To further understand the mechanism, we also took samples from the distal intestine (DI) of some of the fish per diet group. These samples revealed an upregulation of pathways related to lymphatic development and T cell production, as well as activation of TH2 helper cells, adaptive immunity," outlined Øverland.
The team conducted a second study in which they fed salmon the optimal dose of fucoidan during the seawater transfer, a critical phase for salmon due to the multiple stressors and high mortality rates associated with it.
“The fish were also exposed to a pathogen, and we observed an increase in the production of antimicrobial peptides—essential for enhancing the fish’s resilience and preventing pathogen outbreaks. The results were so promising that we proceeded with a third experiment. In this challenge trial, Atlantic salmon were fed fucoidan-enriched diets and exposed to Tenacibaculum dicentrarchi, a bacterium responsible for winter ulcers, after seawater transfer.”
Winter ulcers, which are common during cold water and high salinity periods, have been a persistent issue for farmed salmon, particularly in Norway and Chile.
“Our goal was to determine whether this functional feed could protect the fish against the pathogen. In Chile, we saw a significant reduction in mortality rates, which further demonstrated the potential of seaweed extracts as functional feed ingredients to improve fish health and resilience," noted Øverland.
Seaweed extracts can benefit broiler chickens
The team has also assessed fucoidan in broiler chickens. In a study with 240 chickens, various levels of fucoidan were added to their diets over 28 days. While feed intake and growth rate were not affected, the inclusion of 1g fucoidan/kg feed improved feed conversion efficiency and protein digestibility.
Fucoidan also appeared to enhance gut health and activated immune responses in the birds. However, as seen in previous studies, the right inclusion level is crucial for optimal results, stressed Øverland.
Ruminant research
In addition, the researchers evaluated seaweed inclusion in ruminant rations.
Ruminants from goats to dairy cows can utilize less-processed seaweed due to their rumen’s fermentation capacity, said Øverland. “Ruminants can use the whole biomass.”
“We evaluated sugar kelp in the diets of several ruminant species, working closely with industry partners to track the entire seaweed value chain—from cultivation and harvesting to processing—before incorporating it into total mixed rations for the animals. When feeding dairy cows or beef cattle, it's important to stay within legal limits for iodine and arsenic, so we processed the seaweed by blanching to reduce these levels.
“In collaboration with Seaweed Solutions, we harvested and processed the seaweed, then transported it frozen to our university. There, we chopped it using a silage cutting machine, and some of the seaweed was also dried in the sun for 24 hours while we monitored the dry matter content to ensure it matched that of the silage. Afterward, we incorporated the seaweed into the animal feed,” added the feed expert.
The team assessed its use in a lamb diet to evaluate its effects on meat quality and nutritional value. Female Norwegian White lambs, six months old, were fed three different diets for 35 days before slaughter: a control diet (CON) and two seaweed-supplemented diets (SW), containing either 2.5% (SW1) or 5% (SW2) sugar kelp. The results showed that seaweed supplementation had positive effects on cooking loss, shear force, color stability, and oxidative stability in the meat during chilled storage. Additionally, the seaweed enriched the lamb meat with iodine and helped stabilize selenium content, said Øverland.
“We found the results with lambs so interesting that we decided to conduct another study with bulls.”
That study looked at how blanched seaweed affected the diets of finishing bulls and the quality of their meat. The team used a maximum of 0.8% dry matter of blanched kelp in their diets to stay within safe limits for iodine and arsenic. Nineteen Limousin crossbreed bulls were divided into two groups: one received a control diet, while the other was fed the diet supplemented with seaweed for 48 days before slaughter. The bulls on the seaweed diet had heavier carcasses, but both groups had similar fat levels.
“We didn’t observe any differences in feed intake. However, we did see similar trends to those noted with the lambs, including a reduction in cooking loss, a trend towards increased tenderness of the meat, and positive effects on the selenium and iodine content in the meat.”
Milk production
“We also wanted to find out if adding seaweed to dairy cow diets could improve their milk production and help increase iodine intake for people in Norway," said Øverland.
To do this, the team conducted a study with six Norwegian Red dairy cows. They were fed a diet of grass silage and concentrate, either with 1% sugar kelp (Saccharina latissima) added (the SW diet) or without it as a control (the CON diet).
They looked at how the seaweed affected how much the cows ate, how much milk they produced, and the milk’s chemical makeup. The results showed that the cows on the SW diet ate significantly more than those on the control diet. This increase in feed intake likely led to a significant boost in milk production, reported the team. The SW diet also tended to increase the fat content in the milk, resulting in more energy-corrected milk (ECM) than the control diet. Additionally, the cows on the SW diet produced more fat and protein in their milk. A key finding was that the iodine content in the milk from cows on the SW diet was seven times higher than in the control group.
Processing innovation
Overall, Øverland said the team’s research findings highlight the potential of seaweed extracts to improve animal health, making them a promising ingredient for functional feeds in aquaculture and chicken production while the use of seaweed biomass can improve several aspects of ruminant production.
But further research is needed to optimize seaweed processing techniques and accelerate the growth of the industry in Norway, she concluded.