By Sofie Jackson & Antony Clements-Thrower A dog walker suffered life-changing injuries when a number of cows trampled her in a field, forcing her to escape the danger by climbing a tree. Janicke Tvedt, 57, and her friend David Hood had set out on a popular walk with Labrador Goose across fields and public rights of way near Shaws Farm in Ripon. When they spotted a number of cows, they left the field through a hedge. But then they came across a lone cow and a calf which attacked their pet. When Janicke went to save her dog, she was knocked to the ground and trampled, forcing her and Mr Hood to…