Clover causeing collic in horse?

So this lady i'm riding for has 3 horses and their out year round but shes afraid if she just turns her horses out onto her beautiful pasture that their going to colic cause of the good amount of clover so shes sectioning off parts of the pasture at a time to let them graze on. Now im pretty sure none of them have a history of colic. it seems like alot of work to move the electric fencing every few days and she watches them pretty closely as it is should i tell her it would be ok to just let them out to graze during the day then turn them onto dry lot at night?