Donkey Heart Rate and Heart Rate Variability: A Scoping Review

Abstract

Heart rate (HR) and heart rate variability (HRV) are commonly used physiological measures in animals. While several studies exist on horse HRV, less information is available for donkeys. This scoping review aims to understand the extent and type of published evidence on donkey HR and HRV, their clinical and research applications, the devices used, and the analysis performed. Only quantitative primary studies published in English were considered. Four different databases were queried through the Web of Science platform, with additional evidence identified by citation chasing. After a two-stage screening phase, data were extracted considering study and population characteristics, information on HR/HRV analysis, and applications. The majority of the 87 included articles (about 80%) concerned a sample size of up to 20 individuals and were published since 2011 (about 65%). Forty-one articles employed an electronic device for signal acquisition (mainly electrocardiographs and heart rate monitors), yet only two articles reported HRV parameters. The literature on donkey HRV is lacking, and this gap can be filled by gaining knowledge on donkey characteristics and finding useful tools for welfare assessment. Comparison with what is known about the horse allows a discussion of the technical and interpretative difficulties that can be encountered with donkeys.

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“…As for HRV analysis, the only parameter that varied significantly when comparing the (+) and (−) tests and their respective phases (pre, test, and post) was rMSSD, a parameter reflecting short-term changes in HRV due mainly to parasympathetic nervous system activity [34,51]. rMSSD was significantly lower in the 'post' (−) test phase than in both the 'pre' (−) test/(−) 'test' phases, and the 'post' (+) test phase.…”

“…On the contrary, based on what was reported by other authors, ultra-short segments of one minute were considered [33,84]. Other unresolved issues concerning the analysis of HRV in donkeys, which is still in its infancy, were previously discussed in a scoping review on HR and HRV in donkeys [34]. This review also revealed that only two other studies have so far analysed HRV in donkeys [35,36], which makes our results difficult to compare and, thus, need to be interpreted with caution.…”

“…Specifically, HRV measures fluctuations in the time interval between successive heartbeats, which are regulated by the autonomic nervous system [32,33]. In donkeys, this parameter has been studied as an indicator of stress by two studies so far [34], one comparing HRV parameters with two different training methods [35], the other analysing HRV variation before, during, and after an AAI session [36]. In contrast, HRV analysis was performed more frequently in horses, where it was used to investigate their emotional state in response to different stimuli [37][38][39][40].…”