> I don't have any comparisons of the fatty acid content and profile of
> popular sources of red meat between, for example:
> (b) grass-fed farmed cattle
> (c) feedlot

Marketplace compared the fatty acid content of grass-fed vs feedlot beef:
www.cbc.ca/consumers/market/files/food/beef/test_results.html

Note that the omega-3 fatty content was the same in both samples tested.
The feedlot beef had three times the omega-6 fatty acid of the grass-fed
beef however.  Saturated fat was also elevated in the feedlot beef.  Note
that neither group had antibiotic residues in the samples tested.

Here's the beginning of the story:
www.cbc.ca/consumers/market/files/food/beef/

Rob