Timeline of the experiment.

From the age of 7 days until the end of the experiment at the age of 28 days, animals of the stressed group were exposed to three stressors, including overcrowding, deprivation of cage enrichment, and mixing with unfamiliar animals (dark grey). The latter was paused for 24h before saliva collection (hatched area). The time points at which the body weight was recorded for weight gain (green), the hair was shaven for its cortisol determination (orange), and saliva was sampled for iTRAQ analysis, cortisol determination, and PRM validation (blue) are indicated.