Efficacy of pain management for cattle castration: A systematic review and meta-analysis.

Much research has assessed methods of pain control for cattle castration, but there remains a lack of consensus regarding best practice. We conducted a systematic review and meta-analysis of published research including both an untreated control (i.e. castrated without pain mitigation) and at least one unimodal or multimodal analgesia treatment (i.e. castrated with a local anaesthetic alone, or in combination with a non-steroidal anti-inflammatory drug) to summarise findings on castration pain management. Studies were included if they castrated by surgery, elastration or crushing, and reported at least one of the following outcomes: cortisol, change in bodyweight, foot stomping, wound licking, a subjective assessment of pain using a visual analogue scale, or stride length. Our search identified 383 publications, of which 17 were eligible for inclusion. Most publications focused on surgical castration (n = 14), and the most frequently reported outcome was blood cortisol (n = 13). None of the included studies were assessed as having a low risk of bias, mostly due to a lack of reporting blinding procedures and reasons for missing data. Using a three-level random effect model, we concluded that multimodal analgesia reduced blood cortisol concentrations in the first hour following surgical castration in comparison to the control group; this effect was diminished but still evident at 3 and 4 h, but not beyond at 6, 12 and 24 h. Too few data were available to meaningfully assess other outcomes and methods. Variability in methods and outcomes between studies, and risks of bias, hinder our capacity to provide science-based recommendations for best practice.