The potential of seaweed to reduce methane emissions from livestock is real, but a balance needs to be struck between maintaining animal health, food quality and sustainable practices, according to newly published research on the topic.
Studies to date with red seaweeds fed to ruminants such as cattle, where the active compound in the seaweed is bromoform, found reductions in the region of 60% to 90%, says the scientific review by AgResearch scientist Dr Goldy de Bhowmick and senior scientist Maria Hayes from the Irish agriculture and food development authority, Teagasc.
Other studies, with brown and green seaweeds, showed reductions in methane production of between 20% and 45% in the lab, and 10% in animals, according to the review carried out as part of the SeaSolutions Project funded by the European Research Area on Sustainable Animal Production.
Tools to reduce on-farm methane emissions are being urgently sought by farmers to help meet the New Zealand government’s stated methane reduction targets. Farmers are also facing the prospect of emissions pricing being introduced that will impose costs based on methane emissions.
The effectiveness of seaweed and seaweed extracts is currently being tested in research involving NZ industries and scientists.
“Benefits of feeding seaweeds to ruminants are seaweed-specific and animal species-dependent,” the review published in the Global Challenges journal says.
“In some instances, positive effects on milk production and performance are observed where selected seaweeds are fed to ruminants, while other studies note reductions in performance traits. A balance between reducing methane and maintaining animal health and food quality is necessary.”
Seaweeds are a source of essential amino acids and minerals, and offer huge potential for use as feeds for animal health maintenance once formulations and doses are correctly prepared and administered.
“A negative aspect of seaweed use for animal feed currently is the cost associated with wild harvest and indeed aquaculture production and improvements must be made here if seaweed ingredients are to be used as a solution to control methane production from ruminants for continued production of animal/ruminant sourced proteins in the future,” the review says.
Recent studies have indicated that the compound bromoform in seaweed species such as asparagopsis has adverse effects on the environment and human health, thereby limiting its widespread use. This includes potential damage to the ozone layer when released into the atmosphere and the risk of toxicity related to the presence of bromoform residues in the milk or urine of lactating cows.
“Although mitigation of enteric methane (generated from the rumen) seems to be a very promising approach to reduce emissions, further refinement is needed especially considering the associated negative environmental and health implications,” the review says.
Globally, demand for seaweed for use as animal feed has increased in recent years. It is a recognised source of vitamins and minerals and is often found as an ingredient in dietary supplements for animals, especially ruminants in the form of licks or salt additives.
The review says that in general, consumption of seaweeds for human use does not compete with consumption of seaweed species for livestock use.
De Bhowmick says future research may focus on identifying alternative bioactive compounds in seaweed such as carbohydrates, lipids, peptides and polyphenols. Previous studies and a few initial trials suggest that these bioactive compounds have the potential to inhibit methanogens (microorganisms in the rumen that produce methane).
More: Read the full research paper here.
This article first appeared in the October edition of our sister publication, Dairy Farmer.