HORNS

The horns of domestic ruminants have osseous bases provided by the cornual processes of the frontal bones.

Figure 10-17 Left forelimb (on the left) and left hindlimb (on the right) of the horse, caudal view.

Unlike antlers, which are shed and replaced yearly, horns are permanent and grow continuously after their first appearance soon after birth.

The dermis is tightly adherent to the cornual process and bears numerous short papillae that are slanted api­cally, which ensures that the horn elongates as well as thickens as it grows (Figure 10-22). The horn substance resembles that of the hoof in being an admixture of tubules and intertubular horn. The horn (epiceras) pro­duced by the epidermis at the base is soft and somewhat transparent, resembling the periople of the hoof. It gives the horn its glossy sheen.

In general, horns are found in both sexes, although obviously not in naturally polled breeds, but those of males are usually more massive. Their shape is strongly characteristic of the breed and reflects the shape and size of the cornual process. In cattle, these processes are invaded by the frontal sinuses (Figure 10-22/7), which are therefore opened when an adult animal is dehorned.

The horny shell separates from the bony core on maceration, and this explains the (obsolete) zoological designation Cavicornia (hollow-horned animals) some­times given to ruminants with permanent horns. Rumi­nants of the deer family (Cervidae) have antlers and are specifically excluded from this grouping. Antlers are sturdy outgrowths of the skull that are initially covered with skin but become exposed when the skin dies. The dead skin, or velvet, is removed by rubbing it against trees and other objects. The osseous processes lose their blood supply when exposed, die, and are shed, and the animal is left relatively defenseless until a new set of antlers grows next season.