Equine Mastitis Study Guide

Overview and Clinical Importance

Mastitis is defined as inflammation of the mammary gland, most commonly caused by bacterial infection. While mastitis is a major disease in dairy cattle, it occurs relatively infrequently in mares compared to other domestic species. The seemingly reduced incidence in mares can be partially explained by the smaller size and relatively concealed location of the mare's udder, coupled with a smaller storage capacity than cows and goats. Mastitis can affect lactating, peripartum, dry mares, mares at dry-off, or rarely prepubertal foals.

Understanding equine mastitis is essential for the NAVLE as it represents an important differential diagnosis for udder enlargement and can have significant impacts on both mare and foal health, including failure of passive transfer in neonates.

Equine Mammary Gland Anatomy

The equine udder comprises one pair of mammae (two mammary glands), each with a teat. Each mamma is drained by two independent mammary ductal trees, unlike the cow which has four quarters each drained by one ductal system. Thus, each equine teat typically has two orifices through which the main ducts discharge.