The hairless (hr) gene is involved in the congenital hypotrichosis of Valle del Belice sheep.

Congenital hypotrichosis in mammalian species consists of partial or complete absence of hair at birth. The hairless gene is often responsible for this disorder in men, mice and rats. Recent experimental data on Valle del Belice sheep reared in Sicily for milk production, support the genetic control of the ovine hypotrichosis as a Mendelian recessive trait.