Hair care
Scalp hair grows, on average, at a rate of about 1.25 centimeters per month, and shampoos or vitamins have not been shown to noticeably change this rate. Hair growth rate also depends upon what phase in the cycle of hair growth one is actually in; there are three phases. The speed of hair growth varies based upon genetics, gender, age, hormones, and may be reduced by nutrient deficiency (i.e., anorexia, anemia, zinc deficiency) and hormonal fluctuations (i.e., menopause, polycystic ovaries, thyroid disease).
Cass Ole
His mane as seen in the two movies was partially enhanced. Like many American horses, Cass Ole had his mane trimmed into a bridle path. While he did have a long mane typical for his breed, its natural length was about equal to the width of his neck, which is the average maximum length that a horse's mane will grow when not specially groomed. Therefore, to hide his bridle path trimming and to create the long flowing mane that was seen in the movie itself, hair extensions were stitched into his mane to provide a fuller and longer look on camera. To grow a mane past its natural length requires it to be kept in braids, regularly conditioned, takes at least a year's time to achieve significant length, and, like humans, some horses' manes simply will not grow beyond a certain length.