Lassie was a rough Collie, also known as a long-haired Collie. Collies are an American Kennel Club-recognized breed known for their loyalty and high activity levels.
Although Lassie was said to be a female dog, the part was played by several different male collies. This is because males retain their long hair better than females do during the shedding season.
Collies are generally very intelligent and graceful. Males and females have similar characteristics, but females shed their undercoats about three times per year every 2 years. Males shed their undercoats once per year. Despite their long coats, Collies do not need excessive grooming. The coat should be brushed regularly, and it is a good idea to trim back the hair around the feet, ears and face.