Les vacances de Poly (TV series 1963-1964)

Young Pascal is on holiday at a Summer Camp in Brittany while his beloved horse Poly has to stay back home at the farm. Poly becomes lonely and decides to set off on her own across France to find Pascal. It's a long journey for a small horse to undertake but luckily en route she makes a new friend called Tony who plans to help her get there. - IMDb