When we think of an “old” horse, we’re usually referring to a horse that is over the age of 20. However, some horses age more quickly in their late teens, while others in their early 20s still seem like their younger selves. Older horses typically deal with a variety of age-related changes: a) challenges to the immune system; b) hormonal imbalances; c) alterations in nutrient absorption; and d) physical changes in muscle tone and body condition.

Immune function is a critical consideration when it comes to provision of preventive care. Like the chicken and egg dilemma, such a potpourri of physical changes might be the source of decreases in immune function or they might occur because of declining immune function, referred to as inflamm-aging or immunosenescence.

• Immunosenescence is defined as a decreased ability of the immune system to respond to antigens such as foreign proteins.
• Inflamm-aging refers to chronic, low-grade inflammation caused by cytokines, which are signaling molecules that elicit inflammation. 

Certain white blood cells of the immune system—lymphocytes and macrophages—produce inflammatory cytokines as white blood cells age or accumulate cellular debris. Inflammation further exacerbates adverse effects on a horse’s immune system.

In this series of articles on Stable Management, we will look at some special considerations to ensure the health and wellbeing of your older horse.