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Scientists comment on social media posts about the cattle feed additive Bovaer.
Prof Alastair Hay, Professor (Emeritus) of Environmental Toxicology, University of Leeds, said:
“The additive named ‘Bovaer 10’, which is administered to ruminants to reduce methane emissions, was approved as safe to use in the doses specified by the UK Food Standards Agency (FSA) on 29 March 2023.
“To help it reach a view the FSA also enrolled the help of other UK government agencies including the Animal Feed and Feed Additives Joint Expert Group and the Advisory Committee of Animal Feedingstuffs.
“The product has been approved for use in the UK for some 18 months.
“At the doses which are effective in reducing methane levels by some 21 -33% in cattle, the additive (chemical name: 3-nitroxypropanol) has not been shown to harm the animals. Some changes were noted in test animals of enzymes which are markers of liver function, however the changes noted were still within the usual reference ranges and were not considered to be linked directly to the test additive; the doses of additive tested where these changes were seen were over twice the maximum dose which has been approved for animals. Milk yields were unaffected at the dose where some enzyme changes were seen.
“The additive 3-nitroxypropanol (3-NOP) inhibits the enzyme methyl coenzyme M reductase (MCR), the enzyme that catalyzes the final step of methanogenesis in the digestive system of ruminants, like cows, goats and sheep.
“3-NOP is rapidly metabolized to 3-nitroxypropionic acid (3-NOPA) in cattle and 3-NOPA disappears from the plasma of cattle rapidly with most lost over a 3-hour period.
“Tests have been done on the milk of animals receiving 3-NOP and no metabolites were detected. The level of detection was 5 ug (micrograms) per kg of milk. Theoretical studies indicate that levels of 3-NOP possible in milk at the dosing levels proposed are some 100 times less than would occur at the dose accepted by the FSA as safe. The FSA states that a dose of 0.3mg (milligrams) per kilogram body weight is one it judges to be safe.
“The extensive tests on cancer risk indicate that the chemical additive does not damage DNA, is not genotoxic in other words, and that at the doses approved presents no cancer risk. In cancer studies in rodents the chemical was noted to be associated with some benign changes in mesenchymal cells in a few male animals tested (mesenchymal cells are found in many tissues and can be converted to connective tissue, lymphatic tissue, bone or cartilage). However, there is a safety factor of some 170 between the dose at which some benign tumours were seen in rodents and the dose of the additive considered safe by the FSA.
“3-NOP has properties which indicate that it can irritate the eyes and skin. It will be produced in particle sizes which will not penetrate the lungs, but if inhaled will affect the upper airways. Any workers formulating the product, or mixing with animal feed will thus need to wear masks and eye protection.
“Thus, there is no evidence to suggest that at the doses approved for use in animals that the additive is a risk to humans through consumption of milk.
“Given that the majority of humans eat meat and consume dairy products any action which can be shown to limit methane emissions deserves serious consideration and use of 3-NOP seems one such measure.”
An FSA spokesperson said:
“Milk from cows given Bovaer, a feed additive used to reduce methane emissions, is safe to drink. Bovaer has undergone rigorous safety assessments and is approved for use in Great Britain.”
Further information:
Declared interests
Prof Alastair Hay: I have no conflicts of interest to declare.