Filtering?

[TEA20]

Should I filter when transfering the brew from the fermenter to the barrell?

[Jim]

It's unnecessary and almost unheard of to filter home brewed beer.

In any case, there would be no yeast transferred to the barrel to cause secondary fermentation which gives the beer its sparkle (I'm assuming you aren't using a cornie keg - you can force carbonate in those, but not in a plastic pressure barrel).