British indie director Andrea Arnold takes a sharp turn from acclaimed dramatic filmmaking (Red Road, Fish Tank, American Honey) into documentary.  Straightforwardly, and without comment, Cow depicts the life of dairy cow. Conceived by design, serene, sombre Luma is born on a farm and kept permanently pregnant to maximise her production of milk. Through monotonous agribusiness days, the undignified cycle of pumping, impregnation, gestation and birth continues. Filmed over several years, staying as close to Luma as possible using…