Bovidae sheep from the Yehuda mountains. According to the Talmud, a shofar may be made from the horn of any animal from the Bovidae family except that of a cow or calf (Rosh Hashanah, 26a), although a ram is preferable (Mishnah Berurah 586:1). Bovidae horns are made of keratin (the same material as human toenails and fingernails).

The shofar (Hebrew: שופר‎) is a horn, traditionally that of a ram, used for Jewish religious purposes. Shofar-blowing is incorporated in synagogue services on Rosh Hashanah and Yom Kippur.

Source: Wilkipedia