Is mass spec out of the question?

Perform a biochemical methane potential assay. 

Do you mean in cannulated cows or in Rusitec? For Rusitec there are some gas collection bags where you can collect all the gas from the "plastic rumens" and measure it later. Kind regards

I mean

Of rumen fluid, which was compiled from ruminants

(Sheep, goats, cows)

So that his work centrifuges

Under special circumstances

And access to liquid ...?

My question is what are ways to estimate methane from the resulting liquid after centrifugation?

Kind regards for you..