Weight loss or ill thrift is a common presenting complaint for many medical problems of horses. These cases can be frustrating because physical exam
findings, including rectal palpation, are often unremarkable. However, an ordered approach to further evaluation is useful
for equine practitioners to diagnose many medical disorders as well as to determine when referral to a hospital may be the
next logical step. In addition, a standardized approach to horses with weight loss allows the practitioner a more realistic
expectation of what services a referral hospital may or may not be able to provide for their clients.
History and physical examination
During performance of the physical exam on horses with weight loss, it is important to collect a complete history while also
attempting to document the magnitude and time course of weight loss. A helpful tool can be implementation of body weight measurement
(weight tape) and body condition scoring (BCS) during semiannual or annual preventive care visits. Having this information
within the past few months would allow a practitioner to have a comparison basis to better document weight loss.
Performance of a rectal examination on horses with weight loss, especially when results of the remainder of the physical exam
are unremarkable, cannot be overemphasized. Rectal palpation can reveal abdominal masses including neoplasia or abscesses
due to metastatic Streptococcus equi subspecies equi or Corynebacterium pseudotuberculosis infections. In addition, abnormal
kidneys and ureteroliths can be palpated in some horses with chronic renal disease. When performing a rectal exam on a horse
with weight loss, it is important to attempt to reach the mesenteric root by palpating the aorta as far cranially as possible.
The root of the mesentery contains a number of lymph nodes and is a common location for abdominal abscesses.
Next, performing a complete oral exam also cannot be overemphasized. For example, horses referred for evaluation of a poor
appetite have had a stick lodged between diastemata of the upper dental arcades (Figure 1). A complete dental exam is also essential, especially in horses 15 years of age and older in which poor dentition may be
the primary problem (Figure 1).
Figure 1. A stick can be seen lodged between the upper dental arcades in the oral cavity of a horse that presented for weight
loss over the past week along with a decreased appetite (left); dental abnormalities such as the large hook on the caudal
upper cheek tooth (right) can also lead to weight loss and a decreased appetite.
Assessment of management and appetite
Before more serious medical conditions that lead to weight loss (and referral) are considered, it is essential to determine
whether or not the horse is actually consuming an adequate amount of feed daily to maintain body condition. In a group setting
dominant horses may chase younger and less competitive horses away from feed and correction of weight loss may simply require
separation from the group at feeding time or breaking the herd into smaller groups with less of a dominance hierarchy. Next,
during cold weather caloric requirements increase and if feed availability is not increased weight loss can ensue. In this
situation most of the horses in the herd are found to be thin, rather than a single individual. Thus, when the horse in question
is part of a herd, it is important to look at the remaining horses to determine overall body condition of the group: more
severe weight loss in an individual animal would support a medical condition while an overall decrease in condition of the
herd would support a management problem. To further answer the question of whether or not a horse is eating adequately or
not, it is often helpful to offer the horse a flake of hay or a couple of pounds of concentrate feed as part of the initial
evaluation. "Quidding" or dropping of chewed up hay boluses can be observed and the horse's aggressiveness of eating can also