Id love to but dont. We have massive fields (take about 45min to walk round the edge). No one ever poo picks and it really annoys me. If I did it myself you could emagine how long it would take with 40 horses in the field!!
I'm not on DIY as such, we rent a field by the acre, and then can put on it whatever we want ie stables and 20 horses if we please! But we do poo pick every day, although that is up to us, we have 6 acres and 4 ponies, 1 horse all out 24/7 at the moment, until my shelters/stables are built. At my grans we never do. We have 2 1/2 acres and 3 stables in the field, and the fillies are only on it september to march, the rest of the time they are out on the forest. So we chain harrow/manually spread the muck it and leave it for next year! Stables are done once a week as only used as and when they want to, the doors are left open.