You're right about the mare and foal. But this time of the year, cats can do very well hunting on juvenile birds and baby rabbits etc. Healthy cats are prolific hunters and are very good at looking after themselves when required. So move the horses, 50km isn't much, we get mares from all over the world travelling to Ireland to be covered by thoroughbred stallions here, often with very young foals.
Your mare needs good pasture now!!