What means "hunger hair"?

"Hunger hair" is a colloquial term that refers to the long, coarse hairs on the withers and other parts of a horse's body. These hairs are often longer and thicker than the rest of the horse's coat and can be particularly noticeable in winter. The term refers to the idea that these hairs grow more when a horse is underweight due to lack of food or inadequate nutrition. In reality, however, these hairs can also be genetic or due to other factors such as hormonal changes.