Changes of <scp>N</scp>/<scp>L</scp> ratio and cortisol levels associated with experimental training in untrained rhesus macaques

Abstract

BACKGROUND: Animal training prior to beginning an experiment is an essential procedure and a very important course because it may affect the results of hematologic and hormonal variables and the functions influenced by those factors. Because this training inevitably causes animal stress, we wondered how much time is needed for untrained monkeys to recover from stresses associated with experimental training. METHODS: We measured the hematological and stress hormonal (e.g., cortisol) changes on weekly basis before and after experimental monkey chair training in newly acquired rhesus monkeys. RESULTS: The neutrophil-to-lymphocyte (N/L) ratio significantly increased during the initial phase of the training and then gradually decreased after 3 weeks. Elevated serum cortisol levels in the initial phase also significantly decreased after 3 weeks of chair training. CONCLUSIONS: We conclude that at least a 3-week period is needed in monkey chair training for recovery from training stress. These results suggest that many researchers using nonhuman primates should provide enough time (>3 weeks) for adaptation to the experimental environment prior to beginning a study.