Understanding equine melanoma in grey horses — a near-universal condition with variable welfare impacts.
Equine melanoma presents a welfare management challenge unique to grey horses. The near-universal development of these tumours in aging grey horses means management decisions about when to intervene are complex. Many horses carry multiple melanomas for years without significant welfare impairment — the tumours grow slowly and cause minimal local or systemic effects.
Welfare impairment develops when melanomas enlarge significantly or undergo malignant transformation. Large perineal melanomas interfere with defecation and cause chronic straining, discomfort, and faecal retention. Tumours around the eye obstruct vision or cause ocular irritation. Internal metastasis causes systemic signs of malignancy — weight loss, poor performance, and organ dysfunction.
Treatment decisions should be guided by welfare impact. Small, stable, non-interfering tumours may require only monitoring. Rapidly growing or functionally obstructive tumours warrant intervention — surgical excision, cisplatin implants, or immunotherapy. Quality of life assessment guides the transition from active management to palliative care or humane euthanasia.