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Equine veterinary journal2014; 47(1); 36-42; doi: 10.1111/evj.12250

Spontaneous electroencephalographic changes in a castration model as an indicator of nociception: a comparison between donkeys and ponies.

Abstract: Donkeys are believed to be less demonstrative of pain than ponies. Research into comparative sensory processing between these species is required to elucidate these behavioural differences. Objective: To compare changes in the electroencephalogram (EEG) recorded during castration between donkeys and ponies. Methods: Prospective clinical study. Methods: Six ponies and 6 donkeys were castrated under halothane anaesthesia after acepromazine premedication and thiopental anaesthetic induction. Markers were inserted into the EEG recording at the time of skin incision (skin) and emasculation (emasc) for both testicles (T1 and T2) during a closed castration. Raw EEG data were analysed and the EEG variables median frequency (F50 ), total power (Ptot ) and spectral edge frequency (F95 ) derived using standard techniques. Baseline values of F50 , Ptot and F95 for each animal were used to calculate the percentage change from baseline at T1skin, T2skin, T1emasc and T2emasc. Results: Decreased F50 values relative to baseline were observed in 4 ponies and 2 donkeys across all castration time points. In the remaining animals, the F50 value increased compared with baseline. Both donkey and pony groups showed an overall decrease in Ptot values compared with baseline at T1skin, but the magnitude of the decrease was significantly less (P = 0.004) in ponies than in donkeys. Donkeys demonstrated an overall greater increase (P = 0.05) in F95 values at T1skin relative to baseline compared with ponies. Conclusions: Electroencephalographic responses to the noxious stimulus of castration were noted in both donkeys and ponies. Donkeys demonstrated a greater change in Ptot in response to castration than ponies; thus, donkeys appear to demonstrate a cerebral cortical response to a noxious stimulus that is similar to or greater than that in ponies, suggesting that their subtle behavioural expression of pain is not due to a difference in cortical processing of noxious sensory stimuli.
© 2014 EVJ Ltd.
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Publication Date: 2014-04-01 PubMed ID: 24612132DOI: 10.1111/evj.12250Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

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This research examines the differences in response to pain between donkeys and ponies by comparing electroencephalographic (EEG) changes during castration. The findings suggest that despite behavioral differences in expressing pain, donkeys may have similar or even stronger cerebral responses to painful stimuli as ponies.

Research Methods

  • The researchers used a prospective clinical study design.
  • They included six ponies and six donkeys, who were all castrated under halothane anesthesia. The anesthesia was induced with acepromazine premedication and thiopental.
  • The EEG recordings were marked during two points of the castration process – skin incision and emasculation for both testicles.
  • The raw EEG data was analyzed using standard techniques to derive EEG variables: median frequency (F50), total power (Ptot), and spectral edge frequency (F95).
  • These variables were used to calculate the percentage change from baseline during four stages of the surgery, providing a measure of the animals’ neurological response to the painful stimulus.

Results

  • Four ponies and two donkeys showed a decrease in F50 values from baseline across all stages of castration. The remaining animals showed an increase compared to the base level.
  • Both donkeys and ponies showed an overall decrease in the Ptot values at the time of skin incision. However, this decrease was significantly less in ponies than in donkeys.
  • Donkeys demonstrated a larger increase in F95 values during the skin incision stage compared to ponies.

Conclusions

  • The EEG responses to the painful stimulus of castration were noted in both animals, showing that they both experience pain during the process.
  • The changes in the EEG values suggest that donkeys experience a similar or even greater neurological response to painful stimuli compared to ponies.
  • The finding contradicts the behavioral observation that donkeys appear to express less pain compared to ponies, suggesting that the biological processing of pain may be similar in both animals despite differences in their behavior.

Cite This Article

APA
Grint NJ, Johnson CB, Clutton RE, Whay HR, Murrell JC. (2014). Spontaneous electroencephalographic changes in a castration model as an indicator of nociception: a comparison between donkeys and ponies. Equine Vet J, 47(1), 36-42. https://doi.org/10.1111/evj.12250

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 47
Issue: 1
Pages: 36-42

Researcher Affiliations

Grint, N J
  • Animal Welfare and Behaviour Group, School of Veterinary Science, University of Bristol, UK.
Johnson, C B
    Clutton, R E
      Whay, H R
        Murrell, J C

          MeSH Terms

          • Animals
          • Electroencephalography / veterinary
          • Equidae / classification
          • Equidae / physiology
          • Equidae / surgery
          • Extinction, Biological
          • Male
          • Nociception / physiology
          • Orchiectomy / adverse effects
          • Orchiectomy / veterinary
          • Pain Measurement / methods
          • Pain Measurement / veterinary

          Citations

          This article has been cited 5 times.
          1. Raghazli R, Othman AH, Kaka U, Abubakar AA, Imlan JC, Hamzah H, Sazili AQ, Goh YM. Physiological and electroencephalogram responses in goats subjected to pre-and during slaughter stress. Saudi J Biol Sci 2021 Nov;28(11):6396-6407.
            doi: 10.1016/j.sjbs.2021.07.013pubmed: 34764757google scholar: lookup
          2. Orth EK, Navas González FJ, Iglesias Pastrana C, Berger JM, Jeune SSL, Davis EW, McLean AK. Development of a Donkey Grimace Scale to Recognize Pain in Donkeys (Equus asinus) Post Castration. Animals (Basel) 2020 Aug 13;10(8).
            doi: 10.3390/ani10081411pubmed: 32823676google scholar: lookup
          3. de Oliveira MGC, Luna SPL, Nunes TL, Firmino PR, de Lima AGA, Ferreira J, Trindade PHE, Júnior RAB, de Paula VV. Post-operative pain behaviour associated with surgical castration in donkeys (Equus asinus). Equine Vet J 2021 Mar;53(2):261-266.
            doi: 10.1111/evj.13306pubmed: 32525236google scholar: lookup
          4. Cousillas H, Oger M, Rochais C, Pettoello C, Ménoret M, Henry S, Hausberger M. An Ambulatory Electroencephalography System for Freely Moving Horses: An Innovating Approach. Front Vet Sci 2017;4:57.
            doi: 10.3389/fvets.2017.00057pubmed: 28512633google scholar: lookup
          5. Figueroa S, Levionnois OL, Mirra A. Quantitative Variables Derived from the Electroencephalographic Signal to Assess Depth of Anaesthesia in Animals: A Narrative Review. Animals (Basel) 2025 Aug 5;15(15).
            doi: 10.3390/ani15152285pubmed: 40805076google scholar: lookup
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