Documentaries about a Maine organic milk company and a now-defunct lobster processing venture are among the films featured at this year’s Camden International Film Festival. The four-day festival kicks off Thursday with a showing of “Betting the Farm,” the story of a group of Maine dairy farmers who formed their own milk company. The showing will be followed by an opening-night party. In all, more than 70 feature and short films will be shown in Camden and Rockland. The festival includes a two-day conference where independent documentary filmmakers can network, attend panel discussions and workshops, and pitch their films to broadcasters and distributors. Another Maine documentary, “Downeast,” focuses on a Massachusetts man’s unsuccessful efforts to open a lobster-processing plant in eastern Maine. The festival is now in its eighth year.