James Evans has asked the Welsh Government for more information about the use of Bovaer in food products made by the Arla foods group.
The Brecon and Radnorshire MS said at the Senedd that some constituents have raised concerns with him about its long-term safety and potential side effects on animal health, the environment and even human health.
Bovaer is a feed additive that reduces methane emissions from cows and is intended to help reduce the environmental impact of dairy farming.
Mr Evans said: “It would be useful to get a statement from the Government on the tests that have been conducted to assess these risks, particularly in relation to the effects on animal welfare and the potential for residue in meat and dairy products.
“What steps is the Welsh Government taking to ensure comprehensive safety and monitoring of food products containing this substance?”
The Trefnydd, Jane Hutt, said she would share the question with Rural Affairs Minister, Huw Irranca-Davies,
She told Mr Evans: “This is important in terms of the counsultations that have been carried out on regulating animal welfare.
“But it is also a public health issue, so I will raise it with the Cabinet Secretaries accordingly.”