Thank you a lot ubiquitin and Sam2.
If the cow is shechted and found treif, then can it still be mevatel by intentionally mixing it?
I maybe used the wrong word “worse”, I meant to say that standard tests and chemical analysis is a good method for detecting blood (actually I think there is a max concentration allowed for that), I think it is not as good in detecting a mixture of milks from different species, especially if the nonkosher animal’s milk is not extracted mechanically and there are few cells and few species-specifics bacteria in the milk (yet perhaps it’s good enough, say, could a 1% threshold be detected? I am not sure about it), but in regards to finding traifa milk it seems to me it’s useless.