Livestock

Photosensitisation in Cattle: Welfare and Management

How plant and hepatic photosensitisation affects cattle welfare and how it is managed.

Key Facts

Photosensitisation causes severe sunburn-like lesions on unpigmented skin
Primary photosensitisation from St. John's wort and other plants is direct skin damage
Hepatic photosensitisation from liver damage allows phylloerythrin accumulation
Affected cattle must be removed from sunlight immediately

Welfare Considerations

Photosensitisation causes intense welfare suffering — lesions on muzzle, ears, and unpigmented skin cause pain, swelling, and secondary infection. Welfare-focused management identifies the cause (primary plant-based or secondary hepatic), removes affected cattle from sunlight immediately, treats with NSAIDs and topical preparations, and investigates the source of exposure. Hepatic photosensitisation requires investigation of the underlying liver condition.

What You Can Do

Remove cattle showing facial swelling and lesions on unpigmented skin from sunlight immediately
Seek veterinary assessment to determine whether photosensitisation is primary or hepatic
Identify and remove photosensitising plants from grazed pastures