What is this?

What is this?

Observation - What is this? - UK and Ireland. Description: This herb? has cropped up all over my pasture in the last couple of weeks. (end of May/earlyJune) Does anyone know what it is please? I need to know if it is poisonous to sheep/horses.

This herb? has cropped up all over my pasture in the last couple of weeks. (end of May/earlyJune) Does anyone know what it is please? I need to know if it is poisonous to sheep/horses.