There is a similar product made from garlic, that is encapsulated so it just doesn't wash out with the cows saliva, that has a similar effect. You need about 50kg of it per cow, and it kills the methane producing bacteria. Yet the issue (which they no not fully communicate publicly, but one of the lead scientists told me in private), I guess is the same as with the seaweed. It is not all about reducing methane. We need to do a CO2eq calculations, which includes nitrous oxide at a much higher factor.

And there is much more of this GHG coming out of the treated cow. Which almost cancel the methan reduction effect.