Abstract

The serum level of cortisol is been associated with different degrees of stress in a number of wild animal species in the last decades. Physical and chemical restraint are well known as stressful procedures, although they are necessary in many situations like electroejaculation for reproductive research purposes. The aim of this study was to determine the variations in the serum cortisol levels in African lions, comparing both sexes during chemical restraint, and just for the males, before and after electroejaculation. We studied 33 adult African lions (14 females and 19 males) belonging to the Fundação Parque Zoológico de São Paulo. The animals were restrained with xylazine (Rompun®, Bayer do Brasil, São Paulo, Brazil; 2 mg/kg IM) and ketamine (Vetaset®, Fort Dodge, São Paulo, Brazil; 10 mg/kg IM), delivered by dart gun. Three blood samples were serially collected every 20 minutes as soon as the animal was accessible. To assess the serum cortisol before and after electroejaculation, we performed the procedure in 15 adult male lions. After chemical restraint, using the same protocol already described, two blood samples were collected (before and after the electroejaculation). The serum obtained in the two experiments was frozen and stored at −20°C. The tests were performed by radioimmunoassay (RIA) with commercial kits for cortisol (Cortisol DPC MEDLAB®, Los Angeles, CA, USA). The inter- and intra-assay coefficients of variation were lower than 10%. The results were statistically analysed by the Student’s t-test (95%). The mean concentrations and standard deviations for serum cortisol during restraint were 12.02±6.05 µg/dl and 9.95±4.73 µg/dl, for males and females, respectively (p>0.05). Regarding the electroejaculated group, the results obtained before and after the procedure were 12.13±7.15 µg/dl and 10.80±6.25 µg/dl, showing no significant variation (p>0.05). In conclusion, based on the serum cortisol levels, there was no difference between sexes regarding the intensity of the stress response during the chemical restraint procedure. Similarly, there were no significant changes in the degree of stress before and after electroejaculation as well.