A United Nations report has found that gaps exist in understanding the impact of methane mitigators – including red seaweed – on animal and human health, with more knowledge vital before many can be adopted with confidence.
The Food and Agriculture Organisation (FAO) report, Food Safety Implications from the Use of Environmental Inhibitors, drills deep into the key methane and nitrogen inhibitors being researched.
It highlights the strengths and weaknesses of compounds, including their possible toxicity.
One synthetic compound that has had a high profile is bromoform, also found naturally in red seaweed asparagopsis. The report notes variants of bromoform have been linked to cancer, while bromoform itself could not be classified for its carcinogenic risk due to limited evidence at hand.
In analysing red seaweed, the natural source of bromoform, the report notes in studies of up to 147 days there was no detected bromoform in products from treated animals.
However, it also cautions that the use of bromoform-containing seaweeds needs to be thoroughly assessed, given synthetic bromoform was evaluated as a possible human carcinogen.
It also notes signs of inflammation and abnormalities in rumen cell walls of cows fed asparagopsis.
Dr Steve Meller, CEO of red seaweed mitigation company CH4 Global, told Farmers Weekly that, given the amounts in which his product is supplied to animals, there is no risk associated with it.
“There are no residues in the milk, urine or organs etcetera at the levels we feed it at. It is not an issue,” he said.
In March Australian CSIRO head scientist Dr Chris McSweeney told Farmers Weekly he remains cautious about asparagopsis and bromoform, still subject to scrutiny in terms of bromoform’s residue and longer-term implications for sustained feeding.
Other seaweed types have been highlighted in the report for their toxicity and possible residues in food items, depending upon the particular seaweed. The residues include microplastics, persistent pollutants found in the ocean, and bacterial pathogens alongside major concerns about arsenic, cadmium, iodine and salmonella.
Last month NZ Food Safety deputy-director Vincent Arbuckle responded to concerns raised by CH4 Global about its challenges getting approval in NZ to use red seaweed.
Arbuckle noted the FAO report’s concerns about gaps in knowledge, and potential food safety and trade implications.
“That the CH4 product is ‘natural’ is not central to determining its status as an inhibitor because natural products, just like synthetic products, can have risks associated with them,” he said.
He also pointed out that in Australia, methane inhibitor products do not meet the definition in legislation that would subject them to the Australian equivalent of the NZ Food Safety regulator.
“Therefore, even if the Australian regulator felt inhibitors should be regulated, this cannot occur until there is a legislative change.”
The report, which includes input from New Zealand’s Environmental Protection Authority, notes that most research to date on methane inhibitors has focused on productivity improvements, and less on the impact on non-target organisms and human consumption of treated food products.
NZ’s own questionable experience with inhibitors is highlighted in the report.
The synthetic nitrogen inhibitor DCD was pulled from the market 10 years ago after small traces were unexpectedly detected in some milk products.
Some synthetic compounds’ toxicity risks have been underscored, including the likes of anthraquinones used in cosmetics, food colouring and medicines but still classified as “possibly carcinogenic” to humans.
The other high-profile methane mitigator, 3-NOP, trade name Bovaer, has not reported any safety concerns for consumers and no issues have been observed in rats.
Australian researchers are trialling the essential oil product Agolin in conjunction with red seaweed in sheep feeding trials. The report notes that little information is available on essential oil safety in livestock diets.
Arbuckle confirmed there are four applications to NZ Food Safety for urease inhibitors used in nitrogen fertilisers, used to minimise nitrogen losses on application. No applications have been received by the regulator for methane mitigation trademarked products.
