Complex sentence: Farmers in Eastern Canada (east of Manitoba) and most of British Columbia (non-Peace River) are exempt from the CWB's monopsony control of non-feed wheat and barley-these have their own marketing boards, but they are not compulsory.
Split into simpler sentences: Farmers in Eastern Canada (east of Manitoba) and most of British Columbia (non-Peace River) are exempt from the monopsony control of non-feed wheat and barley. Wheat and barley farmers from the East have their own marketing boards but they are not compulsory.