In this traditional rural diet "extra protein" (in addition from what protein you get from potatoes and grains and legumes) is mainly supplied by dairy and eggs.

However, slaughtering a pig or two once a year in the autumn also doesn't imply eating pork once a year, for a single family a single pig provides a quite large amount of various cured/smoked/dried meat products that are consumed over the winter, so you still have some meat products (not in large quantities though) on most days.