O

OAKUM

Medicated hemp used for packing.

OBEL LAMENESS GRADES

A system of rating degrees of lameness resulting from laminitis developed by Niles Obel circa 1948. Obel Grade I features frequent shifting of weight between the feet, no discernible lameness at the walk, and bilateral lameness at the trot. Obel Grade II horses do not resist having a foreleg lifted, nor are they reluctant to walk, but they do show lameness at the walk. Obel Grade III horses do resist having a foreleg lifted, and are reluctant to walk. Obel Grade IV horses will walk only if forced.

OCCLUSION

Blocking of an opening or passage within an animal's body.

OFF

The horse's right side. The side of the horse that faces east when the animal is walking north. Opposite of near.

OFFSET KNEE

See: Bench Knee.

ONYCHOMYCOSIS

Means a fungal disease of the nail or claw. Denotes the decay of the inner hoof wall and the white line as a result of infection by highly adaptable microorganisms. a.k.a: White line disease; Onycholysis.

OPENED-TOED EGGBAR

See: Backwards Shoe.

OSSELETS

Arthritis of the fetlock joint, characterized by hard swelling.

OSSIFICATION

The hardening of soft tissues, such as ligament or cartilage, into bone. This is often a part of the natural aging process.

OSTEO- or OSTE-

Greek prefix meaning bone.

OSTEOLYSIS

Degeneration of bone.

OUT OF

Refers to the horse's maternal parentage. For example: Discovery is out of Ariadne.

OVER-REACHING

A fault in gait which causes the toe of a hind hoof to strike the back of the lateral fore leg or the heel of its hoof or horseshoe. Similar, but not identical, to forging.

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