Stress is one of the major concerns in zoo animal management. There are well-known effects on behavioral patterns,1-4 cardiovascular and immune system,4,8 hypothalamus-pituitary-gonads axis (HPG)1,3,7,8 and ultimately on homeostasis4,8 and reproduction3,7 in different species. Among wild mammals, the cervids are one of the most stress-sensitive groups, which means that their restraint is a very stressful event, and the use of anesthetic or sedative drugs is always advisable in order to reduce the stress level and to enhance the safety of the procedure. Serum cortisol has been used as an indicator of stress level in different species.1-3,5,6,8,9 The aim of this project was to analyze levels of serum cortisol during three different protocols currently used at the São Paulo Zoo for chemical restraint of fallow deer (Dama dama), reflecting potentially different degrees of stress.
Materials and Methods
We studied 63 individuals (30 males and 33 females) maintained in The Zoo Safari/São Paulo Zoo, São Paulo, Brazil, divided in three different protocols as follows: a) xylazine hydrochloride (Rompun®, Bayer do Brasil, São Paulo, Brazil; 5 mg/kg IM) alone in 10 males and 12 females; b) the association of xylazine (3.5 mg/kg IM) and fentanyl citrate (Fentanyl®, Janssen USA; 0.01 mg/kg IM) in 14 males and 11 females; and c) the association of xylazine (2–3 mg/kg IM) and ketamine (Vetaset®, Fort Dodge, São Paulo, Brazil; 5–7 mg/kg IM) in six males and 10 females. All of them were injected by the use of blow darts. Right after the immobilization we collected the first blood sample and two more samples within an interval of 15 or 20 minutes. The serum obtained was frozen and kept in -20°C until assayed at the Department of Animal Reproduction of The Faculty of Veterinary Medicine and Animal Science, University of São Paulo. The levels of serum cortisol were determined by radioimmunoassay (RIA) using the commercial kit (Coat-a-Count® Cortisol, Diagnostic Products Corporation, Los Angeles, CA, USA). The coefficient of variation inter- and intra-assay were lower than 10%. The data obtained were compared by the T-test with 95% of confidence. The final value for each animal was obtained by the mean of the results of the three blood samples.
In the three protocols, the females showed higher levels of cortisol than the males (p<0.05). The results are presented as mean±SD, as follows:
Males - 0.83±0.66 µg/dl and females - 2.22±1.47 µg/dl
Males - 1.03±0.76 µg/dl and females - 2.22±1.86 µg/dl
Males - 1.32±1.11 µg/dl and females - 2.25±1.04 µg/dl
Comparing the different protocols (considering both sexes), the results were: a) 1.61±1.33 µg/dl, b) 1.54±1.45 µg/dl, and c) 1.87±1.15 µg/dl, showing no difference between groups (p>0.05).
The results showed a clear difference between sexes in the three tested protocols, being the cortisol higher in the females. The fallow deer live in groups with males being the dominants and often showing aggressive behavior against females. So, the females probably have higher levels of cortisol normally. The data found also suggested that there were no significant differences in the level of stress among the tested protocols.
The authors would like to thank the staff of the Zoo Safari Park and The São Paulo Zoological Park Foundation for their generous assistance and for the permission to access the animals.
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