All candidates for the Milk Promotion Board shall be natural persons who are milk producers. A vacancy on the Milk Promotion Board during the term of office that represents a dairy cooperative shall be filled by the Milk Promotion Board with a producer from the respective dairy cooperative for the balance of the unexpired term. A vacancy on the Milk Promotion Board during the term of office that represents an elected producer shall be filled by the Milk Promotion Board with a producer from that respective district.