Ensure water sources are not frozen as decreased water intake will increase the risk of colic. This may mean breaking ice on water buckets at least twice daily. Placing a football in the water trough can help stop an ice layer from forming.
Icy conditions can cause laminitis to flare up due to the tearing effect on the laminae from movement on hard rutted surfaces. There is also some evidence that on bright but very cold days, sugar levels can build up in pasture and trigger a laminitic episode in the same way as rich fast growing spring grass can. Make sure you are familiar with the common poisonous plants in Scotland particularly Yew and Rhododendron. With snow covering the grass horses are tempted to eat plants they would not normally touch.