Measurement of fecal corticosterone metabolites as a predictor of the habituation of rhesus macaques (Macaca mulatta) to jacketing

Abstract

Jacket use in NHP is a common practice and is often considered a form of refinement during experiments necessitating extended periods of catheterization. An important consideration when using jackets is the physiologic effects that jacketing has on NHP and its potential to confound research. Several studies have evaluated the stress response and habituation of NHP to various forms of restraint, but none have looked directly at the timeframe necessary for the habituation of rhesus macaques (Macaca mulatta) to jackets. We set out to determine whether 3 d was a sufficient timeframe for this species to become habituated to a jacket, with or without an undershirt, by evaluating 2 major physiologic parameters. After jacket placement, we measured food consumption and collected fecal samples to measure fecal corticosterone metabolites (FCM) daily for 2 wk. FCM measurements for NHP without undershirts were significantly increased for days 2 and 3 after jacketing before returning to baseline levels. FCM measurements for NHP with undershirts were significantly increased for only 1 d after jacketing, suggesting that the undershirt has a positive effect on jacket habituation. There were no measurable differences in food consumption during the jacket habituation period. Furthermore, no significant differences were noted between sexes. These findings suggest that FCM levels return to baseline 3 d after jacketing and could be a useful predictor of jacket habituation in rhesus macaques.

Figure 1.

Primate undershirt and jacket

Figure 2.

Mean FCM values (ng/g) and 95% confidence intervals according to jacketing group (A, jackets only; B, jackets and undershirts). Dashed line indicates the day of jacketing. Asterisks indicate significant changes from baseline. Fecal data on day 6 are omitted due to sedation of macaques for jacket assessments. FCM levels were significantly (P < 0.04) above baseline on days 2 and 3 in macaques that were jacketed only (group A) and on day 1 for those wearing undershirts and jackets. FCM levels were significantly (P = 0.0065) below baseline on day 9 in macaques wearing jackets only and showed a trend toward a significant decrease (P = 0.0570) on day 10 in animals wearing undershirts and jackets.