Pain-related facial expressions, heart rate variability and operator-assessed procedural ease during transvaginal follicular aspiration in mares: effect of procedure, sedation and butylscopolamine bromide - metamizole.

Facial expressions outperform HRV for OPU pain assessment; sedation plus butylscopolamine bromide-metamizole improves equine welfare.

This crossover study evaluated pain assessment methods and analgesic protocols during ovum pick-up (OPU) in six healthy adult mares across three experimental protocols: sham OPU without sedation, sham OPU with sedation, and regular OPU with sedation. Each protocol included five sequential phases assessing heart rate variability (HRV), pain-related facial expressions, operator-assessed procedural ease, and rectal peristaltic wave frequency. HRV parameters were predominantly influenced by sedation status rather than the OPU procedure itself, limiting HRV utility as a specific pain biomarker during OPU. Non-sedated mares exhibited higher heart rate and sympathetic nervous system index with lower parasympathetic activity compared to sedated mares. Pain-related facial expressions increased significantly during ovarian manipulation in non-sedated mares but were not further elevated by follicular puncture itself, suggesting manipulation contributes more to discomfort than needle puncture. Butylscopolamine bromide-metamizole significantly reduced rectal peristaltic waves (from 2.2 ± 1.5 to 0 waves; p < 0.012) in non-sedated mares and improved operator-assessed ease of ovarian handling. Sedation alone also reduced peristaltic activity. The study concludes that behavioral parameters, particularly facial expression scoring, are more sensitive than HRV for pain detection during OPU. These findings underscore the importance of refining multimodal analgesic protocols—including sedation and butylscopolamine bromide-metamizole—to improve equine welfare during reproductive procedures, and they highlight that OPU-associated discomfort is primarily linked to ovarian manipulation rather than follicular puncture.

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