Housing and exercise of dogs: effects on behavior, immune function, and cortisol concentration

We examined the effect of supplemental exercise (either individually or with a conspecific) on the physical and psychological health of dogs by measuring immune, endocrine, and behavioral responses. Forty purpose-bred adult male beagles were assigned to one of four treatment conditions: exercised individually (EI), exercised with a conspecific (EC), nonexercised (NE), or cage control (CC). Each EI dog was removed from its cage, carried to an empty room, and allowed to exercise alone for 20 min/d 3 days a weeks for 12 weeks. Two EC dogs were allowed to exercise together following a similar schedule. To control for potential handling effects, NE dogs were removed from their cages, carried to the exercise room, but immediately returned to their cages, and CC dogs remained in their cages during scheduled exercise periods. Detailed behavioral observations, humoral immune responses to the antigen keyhole-limpet hemocyanin, peripheral blood mononuclear cell subsets, plasma cortisol concentration, body weight, and total and differential white blood cell (WBC) counts were routinely monitored. Results indicated few significant treatment effects on physiologic or behavioral measures. Specifically, EC dogs had lower percentages of B lymphocytes, and EC and EI dogs barked more than did NE or CC dogs. However, some physiologic and behavioral measures changed as a function of time regardless of treatment condition. Most notably, for all dogs over time, WBC counts, plasma cortisol values, and behavioral measures reflecting inactivity decreased, while measures reflecting high activity and abnormal behaviors increased. We concluded that neither exercise treatment substantially altered the physical health of research dogs, and perhaps more importantly, failed to prevent the development of abnormal behavior.