I don't know, is the short answer- no-one here uses dry lots so I guess all English grass is not rich??
I don't think so
My horses are out 24/7 on grass- good, grass.
They are not grain fed at all- only the weaned foals and the stallions and Rabbit get feed- Rabbit has to have it as he has no teeth!!!
He is still out on grass and would be really unhappy if he wasn't.
I understand the need to dry lot in some areas.
Having grass and dry lotting makes no sense to me at all, and I have never had fat show horses either- that takes a bit of work, it is true, but it does not take dry lots!!
And Yes, I do think all the colic and ulcers etc is directly related to the stress put on the digestive system by the unnatural diet.
Horses, any horse, any sort of horse- still a horse wild feral or man made, STILL just a horse- needs fibre 22 o/o 24 hours a day, take it away and you get trouble, simple as that.
Providing fibre that does not make you horse fat is fairly simple- I use chaff (straw and grass chop) to limit my show horses digestible feed intake whilst they are in their stalls but there is no time when they stand with nothing to eat.
I have NO idea where the myth that Minis need to be fed differently started but it is firmly entrenched now.