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Article History

Received: 9 July 2018

Accepted: 7 September 2018

First Online: 19 September 2018

Ethics approval and consent to participate

: Serum samples used in this study were taken by veterinarians whenever apes were anaesthetized for management reasons. Therefore, all samples are fasting samples, comparable to samples in human studies []. Only samples from animals anaesthetized for transfer or health check were included. The respective zoo authorities approved all sample collection, and no ape was anaesthetized for the purpose of this study. Sample collection was approved by zoo authorities under the different regulations of Germany, Netherlands, Switzerland, Portugal, and United Kingdom, the different countries involved in the study. Measuring α-Kl in urine was not feasible because testing urine samples for measures of α-Kl levels revealed that urinary α-Kl is not stable [–]. Furthermore, urine samples stored at − 80 °C and – 20 °C degrade when exposed to room temperature or after repeated freeze-thaw cycles [], emphasizing that urine samples are not an alternative source for assessing α-Kl levels.

: Not applicable.

: The authors declare that they have no competing interests.

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