Complex sentence: Fowl and feathered game were primarily (but not exclusively) served as roasts, less frequently as entrées; furred game was more frequently served as an entrée, less frequently as roast.
Split into simpler sentences: Fowl and feathered game were primarily (but not exclusively) served as roasts, less frequently as entrées. Furred game was more frequently served as an entrée, less frequently as roast.