Do bulls experience pain or stress during electroejaculation? Evidence from electroencephalography, behavioral, hormonal, and metabolite profiling

Vet World Vol.18 April-2025 Article - 2

Research Article

Veterinary World, 18(4): 763-772

https://doi.org/10.14202/vetworld.2025.763-772

Ubedullah Kaka^1,2, Nurhusien Yimer Degu^3,4, Pavan Kumar^5,6, Abubakar Ahmed Abubakar⁵, Yong-Meng Goh⁷, Muhammad Waseem Aslam⁸, Khaleeq Ur Rehman Bhutto⁸, Muhammad Abdul Basit^7,9, Wasim S. M. Qadi¹⁰, Norazlan Mohmad Misnan¹¹, Ahmed Mediani¹⁰, and Khor Kuan Hua¹

1. Department of Companion Animal Medicine and Surgery, Faculty of Veterinary Medicine, Universiti Putra Malaysia, 43400, Selangor, Malaysia.
2. Halal Products Research Institute, Putra Infoport, Universiti Putra Malaysia, 43400, Selangor, Malaysia.
3. Department of Veterinary Sciences, School of Medicine, IMU University, Bukit Jalil, 57000, Kuala Lumpur, Malaysia.
4. Division of Veterinary Reproduction, Faculty of Veterinary Medicine, Universitas Airlangga, 60115, Surabaya, Indonesia.
5. Institute of Tropical Agriculture and Food Security, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
6. Department of Livestock Products Technology, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, Punjab, India.
7. Department of Preclinical Sciences, Faculty of Veterinary Medicine, Universiti Putra Malaysia, 43400, Selangor, Malaysia.
8. Department of Clinical Studies, Faculty of Veterinary Medicine, Universiti Putra Malaysia, 43400, Selangor, Malaysia.
9. Department of Biosciences, Faculty of Veterinary Sciences, Bahauddin Zakariya University, Multan, 60000, Punjab, Pakistan.
10. Institute of Systems Biology (INBIOSIS), Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia.
11. Herbal Medicine Research Centre, Institute for Medical Research, National Institutes of Health, Shah Alam, 40170, Malaysia.

Background and Aim: Electroejaculation (EE) is widely used for semen collection in bulls but raises concerns about animal welfare due to potential pain and stress. The physiological impact of EE on bulls remains a topic of debate, with previous studies yielding inconclusive results. This study aims to objectively evaluate pain and stress responses in bulls subjected to EE using electroencephalography (EEG) alongside hormonal, behavioral, and metabolite profiling.

Materials and Methods: Eight bulls were subjected to EE in three replicates, with physiological and behavioral data collected before, during, and after the procedure. EEG parameters, including median frequency (MF) and total power (Ptot), were analyzed to assess cortical activity indicative of pain and stress. Blood samples were evaluated for stress-related hormones (adrenaline, noradrenaline, β-endorphin, and dopamine), while metabolomic analysis was conducted to identify biochemical alterations associated with stress. Behavioral indicators, including vocalization and muscle spasms, were recorded.

Results: EE induced significant increases (p < 0.05) in stress hormones at ejaculation, which gradually returned to baseline 20 min post-procedure. EEG metrics, such as MF and Ptot, significantly increased during EE (p < 0.05), indicating heightened cortical activity associated with nociception. Metabolomic analysis revealed distinct biochemical shifts, with variations in glucose, taurine, and norepinephrine profiles across baseline, stimulation, and recovery phases. Behavioral observations corroborated physiological findings, with bulls exhibiting signs of discomfort, such as struggling, arched back posture, and excessive salivation.

Conclusion: The combined EEG, hormonal, and metabolomic findings confirm that EE is a stressful and painful procedure for bulls. The study provides robust evidence of neurophysiological and biochemical responses indicative of pain. These findings highlight the need for alternative semen collection methods to minimize animal distress and improve welfare standards.

Keywords: bulls, electroejaculation, electroencephalography, hormonal indicators, metabolomics, pain, stress.

How to cite this article: Kaka U, Degu NY, Kumar P, Abubakar AA, Goh YM, Aslam MW, Bhutto KR, Basit MA, Qadi WSM, Misnan NM, Mediani A, and Hua KK (2025) Do bulls experience pain or stress during electroejaculation? Evidence from electroencephalography, behavioral, hormonal, and metabolite profiling, Veterinary World, 18(4): 763-772.

Received: 2024-08-16 Accepted: 2025-03-11 Published online: 2025-04-07

Corresponding author: Ubedullah Kaka and Nurhusien Yimer Degu E-mail: dr_ubedkaka@upm.edu.my and nurhusienyimerdegu@imu.edu.my

DOI: 10.14202/vetworld.2025.763-772

Copyright: Kaka, et al. This article is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/ by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http:// creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.